GERTA KELLER TOPICAL PUBLICATIONS

Cenomanian-Turonian Anoxic Event 2

Micropaleontology in Multi-disciplinary research: Applications to OAE2 and KTB

TitleMicropaleontology in Multi-disciplinary research: Applications to OAE2 and KTB
Publication TypeBook Chapter
Year of Publication2013
AuthorsKeller, G
Book TitleProceedings of XXIII Indian Colloquium on Micropaloentology and Stratigraphy and International Symposium on Global Bioevents in Earth's History
Volume1
ChapterPart I, Pp. 1
EditionSpecial Publication
PublisherGeological Society of India
CityBangalore
ISBN978-93-80998-08-04
Keywordsapplications
URLhttp://www.geosocindia.com/index.php?page=shop.product_details&flypage=flypage-ask.tpl&product_id=227&category_id=20&option=com_virtuemart&Itemid=6

Stratigraphy of the Cenomanian–Turonian Oceanic Anoxic Event OAE2 in shallow shelf sequences of NE Egypt

TitleStratigraphy of the Cenomanian–Turonian Oceanic Anoxic Event OAE2 in shallow shelf sequences of NE Egypt
Publication TypeJournal Article
Year of Publication2011
AuthorsEl-Sabbagh, A, Tantawy, AAAM, Keller, G, Khozyem, H, Spangenberg, J, Adatte, T, Gertsch, B
JournalCretaceous Research
Volume32
Issue6
Pagination705 - 722
Date PublishedJan-12-2011
ISSN01956671
Abstract

Two shallow water late Cenomanian to early Turonian sequences of NE Egypt have been investigated to evaluate the response to OAE2. Age control based on calcareous nannoplankton, planktic foraminifera and ammonite biostratigraphies integrated with δ13C stratigraphy is relatively good despite low diversity and sporadic occurrences. Planktic and benthic foraminiferal faunas are characterized by dysoxic, brackish and mesotrophic conditions, as indicated by low species diversity, low oxygen and low salinity tolerant planktic and benthic species, along with oyster-rich limestone layers. In these subtidal to inner neritic environments the OAE2 δ13C excursion appears comparable and coeval to that of open marine environments. However, in contrast to open marine environments where anoxic conditions begin after the first δ13C peak and end at or near the Cenomanian–Turonian boundary, in shallow coastal environments anoxic conditions do not appear until the early Turonian. This delay in anoxia appears to be related to the sea-level transgression that reached its maximum in the early Turonian, as observed in shallow water sections from Egypt to Morocco.  PDF

URLhttp://linkinghub.elsevier.com/retrieve/pii/S0195667111000474
DOI10.1016/j.cretres.2011.04.006
Short TitleCretaceous Research

Middle and late Cenomanian oceanic anoxic events in shallow and deeper shelf environments of western Morocco

TitleMiddle and late Cenomanian oceanic anoxic events in shallow and deeper shelf environments of western Morocco
Publication TypeJournal Article
Year of Publication2010
AuthorsGertsch, B, Adatte, T, Keller, G, Tantawy, AAAM, Berner, Z, Mort, HP, Fleitmann, D
JournalSedimentology
Volume57
Issue6
Pagination1430 - 1462
Date PublishedJan-10-2010
KeywordsMiddle Cenomanian event, Morocco, oceanic anoxic event 2, palaeoclimate, shallow shelf environments
Abstract

The response of shallow-water sequences to oceanic anoxic event 2 and mid-Cenomanian events 1a and 1b was investigated along the west African margin of Morocco north of Agadir (Azazoul) and correlated with the deep-water sequence of the Tarfaya Basin (Mohammed Beach) based on biostratigraphy, mineralogy, phosphorus and stable isotopes. In the deeper Mohammed Beach section results show double peaks in δ13Corg for mid-Cenomanian events 1a and 1b (Rotalipora reicheli biozone, lower CC10a biozone), the characteristic oceanic anoxic event 2 δ13C excursion (Rotalipora cushmani extinction, top of CC10a biozone) and laminated (anoxic) black shale. In the shallow environment north of Agadir, a fluctuating sea-level associated with dysoxic, brackish and mesotrophic conditions prevailed during the middle to late Cenomanian, as indicated by oyster biostromes, nannofossils, planktonic and benthonic foraminiferal assemblages. Anoxic conditions characteristic of oceanic anoxic event 2 (for example, laminated black shales) did not reach into shallow-water environments until the maximum transgression of the early Turonian. Climate conditions decoupled along the western margin of Morocco between mid-Cenomanian event 1b and the Cenomanian–Turonian boundary, as also observed in eastern Tethys. North of Agadir alternating humid and dry seasonal conditions prevailed, whereas in the Tarfaya Basin the climate was dry and seasonal. This climatic decoupling can be attributed to variations in the Intertropical Convergence Zone and in the intensity of the north-east trade winds in tropical areas.  PDF

URLhttp://doi.wiley.com/10.1111/j.1365-3091.2010.01151.x
DOI10.1111/sed.2010.57.issue-610.1111/j.1365-3091.2010.01151.x

Cenomanian–Turonian transition in a shallow water sequence of the Sinai, Egypt

TitleCenomanian–Turonian transition in a shallow water sequence of the Sinai, Egypt
Publication TypeJournal Article
Year of Publication2008
AuthorsGertsch, B, Keller, G, Adatte, T, Berner, Z, Kassab, AS, Tantawy, AAAM, El-Sabbagh, AM, Stüben, D
JournalInternational Journal of Earth Sciences
Volume99
Issue1
Pagination165 - 182
Date PublishedJan-01-2010
ISSN1437-3254
Abstract

Environmental and depositional changes across the Late Cenomanian oceanic anoxic event (OAE2) in the Sinai, Egypt, are examined based on biostratigraphy, mineralogy, δ13C values and phosphorus analyses. Comparison with the Pueblo, Colorado, stratotype section reveals the Whadi El Ghaib section as stratigraphically complete across the late Cenomanian–early Turonian. Foraminifera are dominated by high-stress planktic and benthic assemblages characterized by low diversity, low-oxygen and low-salinity tolerant species, which mark shallow-water oceanic dysoxic conditions during OAE2. Oyster biostromes suggest deposition occurred in less than 50 m depths in low-oxygen, brackish, and nutrient-rich waters. Their demise prior to the peak δ13C excursion is likely due to a rising sea-level. Characteristic OAE2 anoxic conditions reached this coastal region only at the end of the δ13C plateau in deeper waters near the end of the Cenomanian. Increased phosphorus accumulations before and after the δ13C excursion suggest higher oxic conditions and increased detrital input. Bulk-rock and clay mineralogy indicate humid climate conditions, increased continental runoff and a rising sea up to the first δ13C peak. Above this interval, a dryer and seasonally well-contrasted climate with intermittently dry conditions prevailed. These results reveal the globally synchronous δ13C shift, but delayed effects of OAE2 dependent on water depth.  PDF

URLhttp://link.springer.com/article/10.1007%2Fs00531-008-0374-4
DOI10.1007/s00531-008-0374-4
Short TitleInt J Earth Sci (Geol Rundsch)

Oceanic events and biotic effects of the Cenomanian-Turonian anoxic event, Tarfaya Basin, Morocco

TitleOceanic events and biotic effects of the Cenomanian-Turonian anoxic event, Tarfaya Basin, Morocco
Publication TypeJournal Article
Year of Publication2008
AuthorsKeller, G, Adatte, T, Berner, Z, Chellai, EH, Stüben, D
JournalCretaceous Research
Volume29
Issue5-6
Pagination976 - 994
Date PublishedJan-10-2008
ISSN01956671
Abstract

Profound biotic changes accompanied the late Cenomanian δ13C excursion and OAE2 in planktic foraminifera in the Tarfaya Basin of Morocco. Planktic foraminifera experienced a severe turnover, though no mass extinction, beginning with the rapid δ13C excursion and accelerating with the influx of oxic bottom waters during the first peak and trough of the excursion. Species extinctions equaled the number of evolving species, though only the disaster opportunists Guembelitria and Hedbergella thrived along with a low oxygen tolerant benthic assemblage. The succeeding δ13C plateau and organic-rich black shale deposition marks the anoxic event and maximum biotic stress accompanied by a prolonged drop in diversity to just two species, the dominant (80–90%) low oxygen tolerant Heterohelix moremani and surface dweller Hedbergella planispira. After the anoxic event other species returned, but remained rare and sporadically present well into the lower Turonian, whereas Heterohelix moremani remained the single dominant species. The OAE2 biotic turnover suggests that the stress to calcareous plankton was related to changes in the watermass stratification, intensity of upwelling, nutrient flux and oxic levels in the water column driven by changes in climate and oceanic circulation. Results presented here demonstrate a 4-stage pattern of biotic response to the onset, duration, and recovery of OAE2 that is observed widely across the Tethys and its bordering epicontinental seas.  PDF

URLhttp://linkinghub.elsevier.com/retrieve/pii/S0195667108000773
DOI10.1016/j.cretres.2008.05.020
Short TitleCretaceous Research

Organic carbon deposition and phosphorus accumulation during Oceanic Anoxic Event 2 in Tarfaya, Morocco

TitleOrganic carbon deposition and phosphorus accumulation during Oceanic Anoxic Event 2 in Tarfaya, Morocco
Publication TypeJournal Article
Year of Publication2008
AuthorsHaydon, MP, Adatte, T, Keller, G, Bartels, D, Föllmi, KB, Steinmann, P, Berner, Z, Chellai, EH
JournalCretaceous Research
Volume29
Issue5-6
Pagination1008 - 1023
Date PublishedJan-10-2008
ISSN01956671
Abstract

With a multi-proxy approach, an attempt was made to constrain productivity and bottom-water redox conditions and their effects on the phosphorus accumulation rate at the Mohammed Plage section on the Tarfaya coast, Morocco, during the Cenomanian-Turonian Anoxic Event (OAE 2). A distinct δ13Corg isotope excursion of +2.5‰ occurs close to the top of the section. The unusually abrupt shift of the isotope excursion and disappearance of several planktonic foraminiferal species (e.g. Rotalipora cushmani and Rotalipora greenhornensis) in this level suggests a hiatus of between 40–60 kyrs at the excursion onset. Nevertheless, it was possible to determine both the long-term environmental history as well as the processes that took place immediately prior to and during OAE 2. TOC% values increase gradually from the base of the section to the top (from ∼2.5% to ∼10%). This is interpreted as the consequence of a long-term eustatic sea-level rise and subsidence causing the encroachment of less oxic waters into the Tarfaya Basin. Similarly a reduction in the mineralogically constructed ‘detrital index’ can be explained by the decrease in the continental flux of terrigenous material due to a relative sea-level rise. A speciation of phosphorus in the upper part of the section, which spans the start and mid-stages of OAE 2, shows overall higher abundances of Preactive mass accumulation rates before the isotope excursion onset and lower values during the plateau. Due to the probable short hiatus, the onset of the decrease in phosphorus content relative to the isotope excursion is uncertain, although the excursion plateau already contains lower concentrations. The Corg/Ptotal and V/Al ratios suggest that this reduction was mostly likely caused by a decrease in the available bottom oxygen content (probably as a result of higher productivity) and a corresponding fall in the phosphorus retention ability of the sediment. Productivity appears to have remained high during the isotope plateau possibly due to a combination of ocean-surface fertilisation via increased aridity (increased K/Al and Ti/Al ratios) and/or higher dissolved inorganic phosphorus content in the water column as a result of the decrease in sediment P retention. The evidence for decreased P-burial has been observed in many other palaeoenvironments during OAE 2. Tarfaya's unique upwelling paleosituation provides strong evidence that the nutrient recycling was a global phenomenon and therefore a critical factor in starting and sustaining OAE 2.  PDF

URLhttp://linkinghub.elsevier.com/retrieve/pii/S0195667108000761
DOI10.1016/j.cretres.2008.05.026
Short TitleCretaceous Research

Phosphorus and the roles of productivity and nutrient recycling during oceanic anoxic event 2

TitlePhosphorus and the roles of productivity and nutrient recycling during oceanic anoxic event 2
Publication TypeJournal Article
Year of Publication2007
AuthorsHaydon, MP, Adatte, T, Föllmi, KB, Keller, G, Steinmann, P, Matera, V, Berner, Z, Stüben, D
JournalGeology
Volume35
Issue6
Pagination483
Date PublishedJan-01-2007
ISSN0091-7613
Abstract

Four sections documenting the impact of the late Cenomanian oceanic anoxic event (OAE 2) were studied in basins with different paleoenvironmental regimes. Accumulation rates of phosphorus (P) bound to iron, organic matter, and authigenic phosphate are shown to rise and arrive at a distinct maximum at the onset of OAE 2, with an associated increase in δ13C values. Accumulation rates of P return to pre-excursion values in the interval where the δ13C record reaches its first maximum. An offset in time between the maximum in P accumulation and peaks in organic carbon burial, hydrogen indices, and Corg/Preact molar ratios is explained by the evolution of OAE 2 in the following steps. (1) An increase in productivity increased the flux of organic matter and P into the sediments; the preservation of organic matter was low and its oxidation released P, which was predominantly mineralized. (2) Enhanced productivity and oxidation of organic matter created dysoxic bottom waters; the preservation potential for organic matter increased, whereas the sediment retention potential for P decreased. (3) The latter effect sustained high primary productivity, which led to an increase in the abundance of free oxygen in the ocean and atmosphere system. After the sequestration of CO2 in the form of black shales, this oxygen helped push the ocean back into equilibrium, terminating black shale deposition and removing bioavailable P from the water column.  PDF

URLhttp://geology.geoscienceworld.org/cgi/doi/10.1130/G23475A.1
DOI10.1130/G23475A.1

The Chicxulub Impact and K-T Mass Extinction in Texas

TitleThe Chicxulub Impact and K-T Mass Extinction in Texas
Publication TypeReport
Year of Publication2007
AuthorsKeller, G
Series TitleBulletin of the South Texas Geol. Soc.
Document NumberXLVII (9)
Pagination15-44
Date Published05/2007
InstitutionSouth Texas Geol. Soc.
CitySan Antonio
TypeBulletin
Abstract

The K-T sequences along the Brazos River of Falls County, Texas, provide the most important and critical information regarding the age and biotic effects of the Chicxulub impact outside of Mexico. New investigations based on outcrops and new cores drilled by DOSECC and funded by the National Science Foundation reveal a complex history of three tectonically undisturbed and stratigraphically well-separated events: the Chicxulub impact spherule ejecta layer, a sea-level lowstand sandstone complex, and the K-T mass extinction. The newly discovered Chicxulub impact spherule layer is the oldest of the three events and marks the time of the impact about 300,000 years before the K-T boundary (base of zone CF1), consistent with similar observations from NE Mexico and the Chicxulub crater core Yaxcopoil-l. The sea level lowstand sandstone complex predates the K-T boundary by about 100,000 years and contains clasts with Chicxulub impact spherules eroded from the original impact spherule layer. The third event is the K-T boundary mass extinction, which is not linked to the Chicxulub impact. These results indicate that a combination of impacts (Chicxulub and K-T), volcanism and climate changes caused increasingly stressful environmental conditions that culminated in the end-Cretaceous mass extinction.  PDF

Chicxulub impact predates K–T boundary: New evidence from Brazos, Texas

TitleChicxulub impact predates K–T boundary: New evidence from Brazos, Texas
Publication TypeJournal Article
Year of Publication2007
AuthorsKeller, G, Adatte, T, BERNER, ZSOLT, Harting, M, Baum, G, Prauss, M, Tantawy, A, Stüben, D
JournalEarth and Planetary Science Letters
Volume255
Issue3-4
Pagination339 - 356
Date PublishedJan-03-2007
ISSN0012821X
Abstract

Multidisciplinary studies, including stratigraphy, sedimentology, mineralogy and geochemistry, of the new core Mullinax-1 and outcrops along the Brazos River and Cottonmouth Creek, Falls County, Texas, reveal the complex history of the Chicxulub impact, the event deposit and the K–T boundary event. The K–T boundary, as identified by the negative δ13C shift, first occurrence of Danian planktic foraminifera and palynomorphs occurs 80 cm above the event deposit in core Mullinax-1. The underlying 80 cm interval was deposited in a shallow low oxygen environment during the latest Maastrichtian, as indicated by high stress microfossil assemblages, small shells and burrows infilled with framboidal pyrite. The underlying event deposit, commonly interpreted as K–T impact tsunami, consists of a basal conglomerate with clasts containing Chicxulub impact spherules, repeated upward fining units of spherule-rich sands, followed by hummocky cross-bedded and laminated sands, which are burrowed by Thalassinoides, Planolites and Ophiomorpha and truncated by erosion. This suggests a series of temporally separated storm events with recolonization of the ocean floor by invertebrates between storms, rather than a series of waning tsunami-generated waves. The lithified clasts with impact spherules at the base of the event deposit provide strong evidence that the Chicxulub impact ejecta layer predates the event deposit, but was eroded and re-deposited during the latest Maastrichtian sea level lowstand. The original Chicxulub ejecta layer was discovered in a 3 cm thick yellow clay layer interbedded in undisturbed late Maastrichtian clay- and mudstones 40 cm below the base of the event deposit and near the base of planktic foraminiferal zone CF1, which spans the last 300 kyr of the Maastrichtian. The yellow clay consists of cheto smectite derived from alteration of impact glass, as indicated by rare altered glass spherules with similar chemical compositions as reworked spherules from the event deposit and Chicxulub impact spherules from NE Mexico and Haiti. The Brazos sections thus provide strong evidence that the Chicxulub impact predates the K–T boundary by about 300 kyr, consistent with earlier observations in NE Mexico and the Chicxulub crater core Yaxcopoil-1.  PDF

URLhttp://linkinghub.elsevier.com/retrieve/pii/S0012821X06009162
DOI10.1016/j.epsl.2006.12.026
Short TitleEarth and Planetary Science Letters

Basinward transport of Chicxulub ejecta by tsunami-induced backflow, La Popa basin, NE Mexico: COMMENT

TitleBasinward transport of Chicxulub ejecta by tsunami-induced backflow, La Popa basin, NE Mexico: COMMENT
Publication TypeJournal Article
Year of Publication2005
AuthorsKeller, G, Adatte, T
JournalGeology
Volume33
Paginatione88
Abstract

Lawton et al. (2005) describe valley-like deposits in the continental to shallow marine La Popa basin northwest of Monterrey, Mexico, and interpret these as the result of Chicxulub impact induced-tsunami backflow. They further speculate that the thick siliciclastic units, known from the deep paleocanyons of the continental slope to the south and southeast, can also be explained as tsunami backflow deposits. We find no evidence to support this notion in their paper or in more than 45 exposures we examined to the south. Below we comment on their tsunami backflow interpretation and the lack of evidence from Mexico to Texas.  PDF

URLhttp://geology.gsapubs.org/content/33/1/e88.1.short
DOI10.1130/0091-7613-33.1.e88

Impacts, volcanism and mass extinction: random coincidence or cause and effect?

TitleImpacts, volcanism and mass extinction: random coincidence or cause and effect?
Publication TypeJournal Article
Year of Publication2005
AuthorsKeller, G
JournalAustralian Journal of Earth Sciences
Volume52
Issue4-5
Pagination725 - 757
Date PublishedJan-09-2005
ISSN0812-0099
Abstract

Large impacts are credited with the most devastating mass extinctions in Earth's history and the Cretaceous – Tertiary (K/T) boundary impact is the strongest and sole direct support for this view. A review of the five largest Phanerozoic mass extinctions provides no support that impacts with craters up to 180 km in diameter caused significant species extinctions. This includes the 170 km-diameter Chicxulub impact crater regarded as 0.3 million years older than the K/T mass extinction. A second, larger impact event may have been the ultimate cause of this mass extinction, as suggested by a global iridium anomaly at the K/T boundary, but no crater has been found to date. The current crater database suggests that multiple impacts, for example comet showers, were the norm, rather than the exception, during the Late Eocene, K/T transition, latest Triassic and the Devonian – Carboniferous transition, but did not cause significant species extinctions. Whether multiple impacts substantially contributed to greenhouse warming and associated environmental stresses is yet to be demonstrated. From the current database, it must be concluded that no known Phanerozoic impacts, including the Chicxulub impact (but excluding the K/T impact) caused mass extinctions or even significant species extinctions. The K/T mass extinction may have been caused by the coincidence of a very large impact (> 250 km) upon a highly stressed biotic environment as a result of volcanism. The consistent association of large magmatic provinces (large igneous provinces and continental flood-basalt provinces) with all but one (end-Ordovician) of the five major Phanerozoic mass extinctions suggests that volcanism played a major role. Faunal and geochemical evidence from the end-Permian, end-Devonian, end-Cretaceous and Triassic/Jurassic transition suggests that the biotic stress was due to a lethal combination of tectonically induced hydrothermal and volcanic processes, leading to eutrophication in the oceans, global warming, sea-level transgression and ocean anoxia. It must be concluded that major magmatic events and their long-term environmental consequences are major contributors, though not the sole causes of mass extinctions. Sudden mass extinctions, such as at the K/T boundary, may require the coincidence of major volcanism and a very large Impact.  PDF

URLhttp://www.tandfonline.com/doi/abs/10.1080/08120090500170393
DOI10.1080/08120090500170393
Short TitleAustralian Journal of Earth Sciences

Basinward transport of Chicxulub ejecta by tsunami-induced backflow, La Popa basin, NE Mexico: Comment and Reply: COMMENT

TitleBasinward transport of Chicxulub ejecta by tsunami-induced backflow, La Popa basin, NE Mexico: Comment and Reply: COMMENT
Publication TypeJournal Article
Year of Publication2005
AuthorsStinnesbeck, W, Schafhauser, A, Götz, S
JournalGeology
Volume33
Paginatione86
Abstract

Valley-fi ll deposits in the continental to shallow marine La Popa basin to the northwest of Monterrey, Mexico, are interpreted by Lawton et al. (2005) as the result of Chicxulub impact-induced tsunami backfl ow. There is little if any support for this notion in their paper and it contradicts their earlier publication on the same outcrops (Lawton et al., 2001).  PDF

URLhttp://geology.gsapubs.org/content/33/1/e86.short
DOI10.1130/0091-7613-33.1.e86

High-resolution geochemical record of Cretaceous-Tertiary boundary sections in Mexico: New constraints on the K/T and Chicxulub events

TitleHigh-resolution geochemical record of Cretaceous-Tertiary boundary sections in Mexico: New constraints on the K/T and Chicxulub events
Publication TypeJournal Article
Year of Publication2005
AuthorsStüben, D, Kramar, U, Harting, M, Stinnesbeck, W, Keller, G
JournalGeochimica et Cosmochimica Acta
Volume69
Issue10
Pagination2559 - 2579
Date PublishedJan-05-2005
ISSN00167037
Abstract

The investigation of eight Cretaceous–Tertiary (K/T) sections in Mexico, based on major and trace element, platinum group element (PGE), stable isotope, and multivariate statistical analysis, reveals a complex depositional history across the Chicxulub and K/T boundary events. At the biostratigraphically determined K/T boundary, a minor but significant Ir-dominated PGE anomaly (0.2– 0.8 ng/g) is present in most sections. This Ir anomaly originated from an impact event and is always stratigraphically and geochemically decoupled from the underlying spherule-rich ejecta deposit related to the Chicxulub event. In all sections examined, one to three glass spherule ejecta layers and one or two chondrite-dominated PGE anomalies are separated by a bioturbated siliciclastic deposit and/or hemipelagic marl, which indicates the occurrence of at least two impact events separated by a considerable amount of time. In addition, bentonite layers and Pt and Pd-dominated PGE anomalies below and above the K/T boundary indicate volcanic activity. Above the K/T boundary, reduced bioproductivity is documented by a decrease in the biogenically bound fraction of nutrients and fluctuating ratios of immobile elements (e.g., Ti/Zr). Variations in detrital elements reflect changes in the depositional environment. Carbon and oxygen isotope and trace element distribution patterns indicate a gradually changing climate during the latest Maastrichtian, an abrupt change at the K/T boundary, and a slight recovery during the lowermost Paleocene.  PDF

URLhttp://linkinghub.elsevier.com/retrieve/pii/S0016703704008622
DOI10.1016/j.gca.2004.11.003
Short TitleGeochimica et Cosmochimica Acta

Late Maastrichtian and K/T paleoenvironment of the eastern Tethys (Israel): mineralogy, trace and platinum group elements, biostratigraphy and faunal turnovers

TitleLate Maastrichtian and K/T paleoenvironment of the eastern Tethys (Israel): mineralogy, trace and platinum group elements, biostratigraphy and faunal turnovers
Publication TypeJournal Article
Year of Publication2005
AuthorsAdatte, T, Keller, G, Stüben, D, Harting, M, Kramar, U, Stinnesbeck, W, Abramovich, S, Benjamini, C
JournalBulletin de la Societe Geologique de France
Volume176
Pagination37-55
Abstract

The late Maastrichtian to early Danian at Mishor Rotem, Israel, was examined based on geochemistry, bulk rock and clay mineralogies, biostratigraphy and lithology. This section contains four red clay layers of suspect impact or volcanic origin interbedded in chalk and marly chalks. PGE anomalies indicate that only the K/T boundary red layer has an Ir dominated PGE anomaly indicative of an impact source. The late Maastrichtian red clays have Pd dominated PGE anomalies which coincide with increased trace elements of terrigenous and volcanogenic origins. Deccan or Syrian-Turkey arc volcanism is the likely source of volcanism in these clay layers. Glauconite, goethite and translucent amber spherules are present in the clay layers, but the Si-rich spherules reported by Rosenfeld et al. [l989] could not be confirmed. The absence of Cheto smectite indicates that no altered impact glass has been present. The red layers represent condensed sedimentation on topographic highs during sea level highstands. In the Negev area, during the late Maastrichtian, the climate ranged from seasonally wet to more arid conditions during zones CF3 and CF2, with more humid wet conditions in the latest Maastrichtian zone CF1 and in the early Danian, probably linked to greenhouse conditions. Planktic foraminifera experienced relatively high stress conditions during this time as indicated by the low species richness and low abundance of globotruncanids. Times of intensified stress are indicated by the disaster opportunist Guembelitria blooms, which can be correlated to central Egypt and also to Indian Ocean localities associated with mantle plume volcanism. Marine plankton thus support the mineralogical and geochemical observations of volcanic influx and reveal the detrimental biotic effects of intense volcanism.  PDF

URLhttp://bsgf.geoscienceworld.org/content/176/1/37.abstract
DOI10.2113/176.1.37

Age and paleoenvironment of the Cenomanian–Turonian global stratotype section and point at Pueblo, Colorado

TitleAge and paleoenvironment of the Cenomanian–Turonian global stratotype section and point at Pueblo, Colorado
Publication TypeJournal Article
Year of Publication2004
AuthorsKeller, G, Pardo, A
JournalMarine Micropaleontology
Volume51
Issue1-2
Pagination95 - 128
Date PublishedJan-04-2004
ISSN03778398
Abstract

Biostratigraphy and stable isotopes indicate that the global stratotype section and point (GSSP) at Pueblo contains an essentially complete sedimentary record across the global ocean anoxic event (OAE 2) and the Cenomanian–Turonian boundary. The OAE 2 δ13C shift occurred over a period of about 90 ky and was accompanied by a major sea level transgression, which at its peak was marked by an incursion of oxygen-rich waters creating a benthic oxic zone that lasted about 100 ky. A mid-Cenomanian δ13C shift, sea level transgression and faunal turnover occurred about 2 my before OAE 2. δ18O values of the planktic foraminifer Hedbergella planispira and its relative abundance changes reveal cyclic variations in surface salinity due to alternating freshwater influx and marine incursions, whereas dominance by the low oxygen tolerant Heterohelix species indicates a well-developed oxygen minimum zone (OMZ) for most of the middle to late Cenomanian and early Turonian.

Profound faunal changes accompanied these oceanographic events, including the extinction of 30% of the species assemblage and an equal gain in evolutionary diversification, though the overall combined relative abundances of outgoing and incoming species were less than 2% and 4%, respectively, of the total assemblages. The faunal turnover began with the sea level transgression and rapid increase in δ13C values, and accelerated with the influx of oxygen-rich deep water, increased water mass stratification and competition during the benthic oxic zone. The incursion of oxygen-rich deep waters at this time was also observed in Morocco and may represent a global event of a still unknown source.  PDF

URLhttp://linkinghub.elsevier.com/retrieve/pii/S0377839803001051
DOI10.1016/j.marmicro.2003.08.004
Short TitleMarine Micropaleontology

More evidence that the Chicxulub impact predates the K/T mass extinction

TitleMore evidence that the Chicxulub impact predates the K/T mass extinction
Publication TypeJournal Article
Year of Publication2004
AuthorsKeller, G, Adatte, T, Stinnesbeck, W, üben, D, BERNER, ZSOLT, Kramar, U, Harting, M
JournalMeteoritics & Planetary Science
Volume39
Issue7
Pagination1127 - 1144
Date PublishedJan-07-2004
ISSN10869379
Abstract

Yaxcopoil-1 (Yax-1), drilled within the Chicxulub crater, was expected to yield the final proof that this impact occurred precisely 65 Myr ago and caused the mass extinction at the Cretaceous-Tertiary (K/T) boundary. Instead, contrary evidence was discovered based on five independent proxies (sedimentologic, biostratigraphic, magnetostratigraphic, stable isotopic, and iridium) that revealed that the Chicxulub impact predates the K/T boundary by about 300,000 years and could not have caused the mass extinction. This is demonstrated by the presence of five bioturbated glauconite layers and planktic foraminiferal assemblages of the latest Maastrichtian zone CF1 and is corroborated by magnetostratigraphic chron 29r and characteristic late Maastrichtian stable isotope signals. These results were first presented in Keller et al. (2004). In this study, we present more detailed evidence of the presence of late Maastrichtian planktic foraminifera, sedimentologic, and mineralogic analyses that demonstrate that the Chicxulub impact breccia predates the K/T boundary and that the sediments between the breccia and the K/T boundary were deposited in a normal marine environment during the last 300,000 years of the Cretaceous.  PDF

URLhttp://blackwell-synergy.com/doi/abs/10.1111/maps.2004.39.issue-7http://doi.wiley.com/10.1111/j.1945-5100.2004.tb01133.x
DOI10.1111/maps.2004.39.issue-710.1111/j.1945-5100.2004.tb01133.x

Chicxulub impact predates the K-T boundary mass extinction

TitleChicxulub impact predates the K-T boundary mass extinction
Publication TypeJournal Article
Year of Publication2004
AuthorsKeller, G, Adatte, T, Stinnesbeck, W, Rebolledo-Vieyra, M, J. Fucugauchi, U, Kramar, U, Stüben, D
JournalProceedings of the National Academy of Sciences
Volume101
Issue11
Pagination3753 - 3758
Date PublishedApr-03-2005
ISSN0027-8424
Abstract

Since the early l990s the Chicxulub crater on Yucatan, Mexico, has been hailed as the smoking gun that proves the hypothesis that an asteroid killed the dinosaurs and caused the mass extinction of many other organisms at the Cretaceous-Tertiary (K-T) boundary 65 million years ago. Here, we report evidence from a previously uninvestigated core, Yaxcopoil-1, drilled within the Chicxulub crater, indicating that this impact predated the K-T boundary by ≈300,000 years and thus did not cause the end-Cretaceous mass extinction as commonly believed. The evidence supporting a pre- K-T age was obtained from Yaxcopoil-1 based on five independent proxies, each with characteristic signals across the K-T transition: sedimentology, biostratigraphy, magnetostratigraphy, stable isotopes, and iridium. These data are consistent with earlier evidence for a late Maastrichtian age of the microtektite deposits in northeastern Mexico. PDF

URLhttp://www.pnas.org/cgi/doi/10.1073/pnas.0400396101
DOI10.1073/pnas.0400396101
Short TitleProceedings of the National Academy of Sciences

Low-Diversity, Late Maastrichtian and Early Danian Planktic Foraminiferal Assemblages of the Eastern Tethys

TitleLow-Diversity, Late Maastrichtian and Early Danian Planktic Foraminiferal Assemblages of the Eastern Tethys
Publication TypeJournal Article
Year of Publication2004
AuthorsKeller, G
JournalThe Journal of Foraminiferal Research
Volume34
Issue1
Pagination49 - 73
Date PublishedJan-01-2004
ISSN0096-1191
Abstract

The eastern Tethys, from Israel to Egypt, experienced unusually adverse environmental conditions for planktic foraminifera during the last two million years of the Maastrichtian, as evident by very low species richness, blooms of opportunistic Guembelitria species in surface waters, dominance of low-oxygen-tolerant heterohelicids in subsurface waters, and near absence of deeper dwelling globotruncanids. Comparison of southern Israel (Mishor Rotem section) with central Egypt (Gebel Qreiya section) reveals that adverse conditions intensified towards the south with foraminiferal assemblages mimicking stress conditions of the early Danian, dominated (75– 90%) by Guembelitria blooms. Faunal assemblages indicate an expanded oxygen minimum and dysoxic zone throughout the region, though at the greater depths represented by localities of southern Israel, bottom waters remained aerobic. Primary productivity was extremely low, as indicated by stable isotopes and low total organic content in sediments. These adverse environmental conditions are likely related to the regional paleobathymetry of the tectonically active Syrian Arc that spans Syria to Egypt. The paleorelief of intra-shelf and intra-slope basins of the Syrian Arc, with their differential rates of subsidence and sedimentation, active folding and faulting, likely controlled the intensity of circulation, upwelling, watermass stratification and the extent of the oxygen minimum zone. The late Maastrichtian rapid climate and sea level changes exacerbated these conditions.  PDF

URLhttp://jfr.geoscienceworld.org/cgi/doi/10.2113/0340049
DOI10.2113/0340049
Short TitleThe Journal of Foraminiferal Research

Cenomanian–Turonian and δ13C, and δ18O, sea level and salinity variations at Pueblo, Colorado

TitleCenomanian–Turonian and δ13C, and δ18O, sea level and salinity variations at Pueblo, Colorado
Publication TypeJournal Article
Year of Publication2004
AuthorsKeller, G, BERNER, ZSOLT, Adatte, T, Stüben, D
JournalPalaeogeography, Palaeoclimatology, Palaeoecology
Volume211
Issue1-2
Pagination19 - 43
Date PublishedJan-08-2004
ISSN00310182
Abstract

Stable isotopes of the surface dwelling planktic foraminifera Hedbergella planispira, its abundance variations, and mineralogical analysis of the Cenomanian–Turonian at Pueblo, CO, reveal cyclic variations in surface salinity due to changes in precipitation, freshwater influx, marine incursions and long-term sea-level fluctuations. Hedbergella planispira is a proxy for salinity variations, as indicated by 2–4x more negative δ18O values in intervals of peak abundances as compared to intervals with reduced populations. Negative δ18O values reflect periods of brackish surface waters caused by freshwater influx during wet humid periods, accompanied by increased clastic transport. More positive δ18O values reflect more normal marine salinities as a result of arid periods and/or marine incursions and correlate with intervals of increased biogenic carbonate deposition. The magnitude of salinity variations during the low sea-level of the Hartland Shale is twice that during the sea-level transgression of the Bridge Creek Limestone. The rapid positive δ13C shift that marks the onset of Oceanic Anoxic Event 2 (OAE 2) at Pueblo occurred over a period of about 100 ky (93.90–94.00 Ma), and coincided with the major sea level transgression that culminated in the deposition of the basal Bridge Creek Limestone. A positive δ13C shift also occurred in the Rotalipora cushmani zone prior to OAE 2 and coincided with a sea level rise and enhanced preservation of terrestrial organic matter. The likely cause for OAE 2 is depletion of 12C in the water column as a result of high primary productivity, whereas an earlier R. cushmani zone event was primarily caused by increased input of terrigenous organic matter. Both δ13C events are associated with enhanced organic matter preservation and anoxic or dysoxic bottom waters.  PDF

URLhttp://linkinghub.elsevier.com/retrieve/pii/S0031018204002007
DOI10.1016/j.palaeo.2004.04.003
Short TitlePalaeogeography, Palaeoclimatology, Palaeoecology

Disaster opportunists Guembelitrinidae: index for environmental catastrophes

TitleDisaster opportunists Guembelitrinidae: index for environmental catastrophes
Publication TypeJournal Article
Year of Publication2004
AuthorsKeller, G, Pardo, A
JournalMarine Micropaleontology
Volume53
Issue1-2
Pagination83 - 116
Date PublishedJan-10-2004
ISSN03778398
KeywordsGuembelitria blooms; Volcanism; impacts; K–T; late Maastrichtian
Abstract

Blooms of the disaster opportunist Guembelitria species are proxies for environmental catastrophes, whether impact orvolcanism, leading to severe biotic stress crises that may range from temporary exclusion of ecological specialists and generalists to mass extinctions. During the late Maastrichtian and early Danian (zones P0 and Pla), Guembelitria blooms show global distributions, but with the largest blooms (40–80% Guembelitria) in low and middle latitudes and only minor blooms (10–20%) in high latitudes. Late Maastrichtian Guembelitria blooms are, so far, known from the Indian Ocean and eastern Tethys. The most intense Guembelitria blooms (>60% Guembelitria) occurred in shallow continental shelf areas, slope/shelf margins and volcanic provinces of the Indian Ocean. What these environments have in common is high nutrient influx (eutrophication) either from continental runoff, upwelling along continental margins or volcanic input. At times of biotic crises, Guembelitria blooms may have spread rapidly to the exclusion of most or all other species, much like today’s red tides, but with near global distributions. A simple model can explain the ecological succession and recovery phases that follow major biotic perturbations caused by impacts or volcanism that lead to exclusion of specialist and most generalist species. Within such highly stressed environments, Guembelitria is the only genus to thrive, and without competition, rapidly reproduce and exponentially increase their populations. When nutrients are depleted, populations rapidly decrease, leading to ecologic niches for other generalists and ecosystem recovery. Small low-O2-tolerant heterohelicid populations mark this second stage, followed by small trochospiral and planispiral species. With further environmental recovery, increasing competition, niche development and restoration of a well-stratified water mass, oligotrophic conditions are restored, opening habitats for the highly specialized and diverse species and a return to normal diverse assemblages. This ecological succession is observed in association with mantle plume volcanism in the Indian Ocean and eastern Tethys during the late Maastrichtian, and in association with the K–T impact and volcanism during the early Tertiary.  PDF

URLhttp://linkinghub.elsevier.com/retrieve/pii/S0377839804000672
DOI10.1016/j.marmicro.2004.04.012
Short TitleMarine Micropaleontology

Yaxcopoil-1 and the Chicxulub impact

TitleYaxcopoil-1 and the Chicxulub impact
Publication TypeJournal Article
Year of Publication2004
AuthorsStinnesbeck, W, Keller, G, Adatte, T, Harting, M, Stüben, D, Istrate, G, Kramar, U
JournalInternational Journal of Earth Sciences
Volume93
Issue6
Pagination1042 - 1065
Date PublishedJan-12-2004
ISSN1437-3254
Abstract

CSDP core Yaxcopoil-1 was drilled to a depth of 1,511 m within the Chicxulub crater. An organic-rich marly limestone near the base of the hole (1,495 to 1,452 m) was deposited in an open marine shelf environment during the latest Cenomanian (uppermost Rotalipora cushmani zone). The overlying sequence of limestones, dolomites and anhydrites (1,495 to 894 m) indicates deposition in various carbonate platform environments (e.g., sabkhas, lagoons). A 100-m-thick suevite breccia (894–794 m) identifies the Chicxulub impact event. Above the suevite breccia is a dolomitic limestone with planktic foraminiferal assemblages indicative of Plummerita hantkeninoides zone CF1, which spans the last 300 ky of the Maastrichtian. An erosional surface 50 cm above the breccia/dolomite contact marks the K/T boundary and a hiatus. Limestones above this contact contain the first Tertiary planktic foraminifera indicative of an upper P. eugubina zone P1a(2) age. Another hiatus 7 cm upsection separates zone P1a(2) and hemipelagic limestones of planktic foraminiferal Zone P1c. Planktic foraminiferal assemblages of Zone Plc to P3b age are present from a depth of 794.04 up to 775 m. The Cretaceous carbonate sequence appears to be autochthonous, with a stratigraphic sequence comparable to late Cretaceous sediments known from outside the Chicxulub crater in northern and southern Yucatan, including the late Cenomanian organic-rich marly limestone. There is no evidence that these sediments represent crater infill due to megablocks sliding into the crater, such as major disruption of sediments, chaotic changes in lithology, overturned or deep dipping megablocks, major mechanical fragmentation, shock or thermal alteration, or ductile deformation. Breccia units that are intercalated in the carbonate platform sequence are intraformational in origin (e.g., dissolution of evaporites) and dykes are rare. Major disturbances of strata by the impact therefore appear to have been confined to within less than 60 km from the proposed impact center. Yaxcopoil-1 may be located outside the collapsed transient crater cavity, either on the upper end of an elevated and tilted horst of the terrace zone, or even outside the annular crater cavity. The Chicxulub site thus records a large impact that predates the K/T boundary impact and mass extinction.  PDF

URLhttp://link.springer.com/10.1007/s00531-004-0431-6http://www.springerlink.com/index/pdf/10.1007/s00531-004-0431-6
DOI10.1007/s00531-004-0431-6
Short TitleInt J Earth Sci (Geol Rundsch)

The non-smoking gun

TitleThe non-smoking gun
Publication TypeWeb Article
Year of Publication2003
AuthorsKeller, G, Adatte, T, Stinnesbeck, W
Description13(11): 8-11
PublisherGeoscientist
CityLondon
Abstract

This conclusion was announced by Keller, Stinnesbeck and Adatte at the April (2003) EGU-AUG meeting in Nice, France, based on over 10 years of KT research (1) culminating with the new drill core Yaxcopoil-1 in the Chicxulub crater. This evidence has triggered a renewed debate over the cause and impact location of the KT mass extinction and the role of Chicxulub. A public debate is sponsored by the Geological Society of London beginning with its November 1 (2003) issue of Geoscientist.  PDF

Biotic effects of impacts and volcanism

TitleBiotic effects of impacts and volcanism
Publication TypeJournal Article
Year of Publication2003
AuthorsKeller, G
JournalEarth and Planetary Science Letters
Volume215
Issue1-2
Pagination249 - 264
Date PublishedJan-10-2003
ISSN0012821X
KeywordsBiotic effects, Cretaceous–Tertiary, DSDP Site 216, Impacts, Maastrichtian, Volcanism
Abstract

The biotic effects of late Maastrichtian mantle plume volcanism on Ninetyeast Ridge and Deccan volcanism mirror those of the Cretaceous–Tertiary (KT) mass extinction and impact event. Planktonic foraminifera responded to high stress conditions with the same impoverished and small-sized species assemblages dominated by the disaster/opportunists Guembelitria cretacea, which characterize the KT mass extinction worldwide. Similar high stress late Maastrichtian assemblages have recently been documented from Madagascar, Israel and Egypt. Biotic effects of volcanism cannot be differentiated from those of impacts, though every period of intense volcanism is associated with high stress assemblages, this is not the case with every impact. The most catastrophic biotic effects occurred at the KT boundary (65.0 Ma) when intense Deccan volcanism coincided with a major impact and caused the mass extinction of all tropical and subtropical species. The Chicxulub impact, which now appears to have predated the KT boundary by about 300 kyr, coincided with intense Deccan volcanism that resulted in high biotic stress and greenhouse warming, but no major extinctions. The unequivocal connection between intense volcanism and high stress assemblages during the late Maastrichtian to early Danian, and the evidence of multiple impacts, necessitates revision of current impact and mass extinction theories.  PDF

URLhttp://linkinghub.elsevier.com/retrieve/pii/S0012821X0300390X
DOI10.1016/S0012-821X(03)00390-X
Short TitleEarth and Planetary Science Letters

Late Maastrichtian paleoclimatic and paleoceanographic changes inferred from Sr/Ca ratio and stable isotopes

TitleLate Maastrichtian paleoclimatic and paleoceanographic changes inferred from Sr/Ca ratio and stable isotopes
Publication TypeJournal Article
Year of Publication2003
AuthorsStüben, D, Kramar, U, Berner, ZA, Meudt, M, Keller, G, Abramovich, S, Adatte, T, Hambach, U, Stinnesbeck, W
JournalPalaeogeography, Palaeoclimatology, Palaeoecology
Volume199
Issue1-2
Pagination107 - 127
Date PublishedJan-10-2003
ISSN00310182
Abstract

Milankovitch-scale cycles can be recognized in high-resolution δ13C, δ18O, Sr/Ca, mineralogical, and magnetic susceptibility data in hemipelagic sediments that span the last 700 kyr of the Maastrichtian at Elles, Tunisia. Oxygen isotope data reveal three cool periods between 65.50 and 65.55 Ma (21.5-23.5 m), 65.26 and 65.33 Ma (8-11 m), and 65.04 and 65.12 Ma (1.5-4 m), and three warm periods between 65.33 and 65.38 Ma (12-16 m), 65.12 and 65.26 Ma (4-8 m), and 65.00 and 65.04 Ma (0-1.5 m). The cool periods are characterized by small surface-to-deep temperature gradients that reflect intensive mixing of the water column. The surface-to-deep Sr/Ca gradient generally correlates with the oscillating ΔT trend (temperature difference between surface and bottom waters). The carbon isotope composition of planktonic foraminifera indicates a continuous decrease in surface bioproductivity during Late Maastrichtian. Decreasing Δ13C values (difference between the δ13C values of surface and bottom dwelling foraminifera) and the carbon isotope ratios of the planktonic species at the onset of gradual warming at 65.50 Ma reflect a reduction in surface productivity as a result of decreased upwelling that accompanied global warming and possibly increased atmospheric pCO2 related to Deccan Trap volcanism. Time series analysis applied to magnetic susceptibility, δ18O, and Sr/Ca data identifies the 20 kyr precession, 40 kyr obliquity, and 100 kyr eccentricity Milankovich cycles.  PDF

URLhttp://linkinghub.elsevier.com/retrieve/pii/S0031018203004991
DOI10.1016/S0031-0182(03)00499-1
Short TitlePalaeogeography, Palaeoclimatology, Palaeoecology

Fe-rich and K-rich mafic spherules from slumped and channelized Chicxulub ejecta deposits in the northern La Sierrita area, NE Mexico

TitleFe-rich and K-rich mafic spherules from slumped and channelized Chicxulub ejecta deposits in the northern La Sierrita area, NE Mexico
Publication TypeJournal Article
Year of Publication2003
AuthorsSchulte, P, Stinnesbeck, W, Stüben, D, Kramar, U, Berner, Z, Keller, G, Adatte, T
JournalInternational Journal of Earth Sciences
Volume92
Pagination114-142
ISSN1437-3254
KeywordsChicxulub, Ejecta, Iron-rich, K-T boundary, Mafic composition, Mexico, Spherules
Abstract

Spherule deposits, commonly interpreted as ejecta from the Chicxulub impact at Yucatn, Mexico, are present in many K-T (Cretaceous-Tertiary) sections. Geological mapping of the northern La Sierrita area, NE Mexico, revealed the presence of (1) multiple spherule deposits embedded in late Maastrichtian marls, which are folded or disaggregated (breccia-like). They are up to 6 m thick, locally present in two outcrop areas, and show limited lateral continuity. These deposits consist of mm– cm sized spherical to drop-shaped vesiculated spherules, angular to filamentous (ejecta-) fragments and abundant carbonate. They are interpreted as primary ejecta fallout deposits that have been affected by subsequent local slumps-slides, liquefaction, and debris flows; welded components suggest an initial ground surge-like ejectadispersion mode. (2) A spherule deposit, 10–60 cm thick that constitutes the base of a channelized sand-siltstone deposit at, or close to, the K-T boundary and is characterized by wide lateral continuity. It is of similar petrologic composition to deposit (1), though slightly enriched in terrigeneous detritus, thus reflecting influx from proximal shelf areas. It is interpreted to result from debris flows and turbidite currents, though no size sorting and abrasion of ejecta has been observed. Petrological, mineralogical, and geochemical criteria suggest that ejecta components from both types of spherule deposits are similar and originated from the Chicxulub impact, with multiple deposits produced by subsequent remolding, reworking, and redeposition. Spherules and fragments have an Fe- (25–30 wt%), Al-, Mg-rich and Si-poor (<25 wt% SiO2) composition, and are altered to chlorite and iron-oxides, though rare K-rich mafic glass (~50 wt% SiO2; 5–8 wt% K) is also present. They contain Ti-, Fe-, K-rich schlieren, Fe-, Mg-rich globules, and rare m-sized metallic and sulfidic Ni-, Co-rich inclusions. Carbonate as clasts and within spherules and fragments shows textures indicative of quenching and/or liquid immiscibility. Although potential ejecta fractionation and alteration make accurate evaluation difficult, this composition suggests an ejecta origin mainly from mafic lithologies and carbonaceous sediments, in addition to a contribution from intermediate felsic rocks and the possibility of meteoritic contamination.  PDF

URLhttp://dx.doi.org/10.1007/s00531-002-0304-9
DOI10.1007/s00531-002-0304-9

Age and paleoenvironment of the Maastrichtian to Paleocene of the Mahajanga Basin, Madagascar: a multidisciplinary approach

TitleAge and paleoenvironment of the Maastrichtian to Paleocene of the Mahajanga Basin, Madagascar: a multidisciplinary approach
Publication TypeJournal Article
Year of Publication2003
AuthorsAbramovich, S, Keller, G, Adatte, T, Stinnesbeck, W, Hottinger, L, Stüben, D, Berner, Z, Ramanivosoa, B, Randriamanantenasoa, A
JournalMarine Micropaleontology
Volume47
Issue1-2
Pagination17 - 70
Date PublishedJan-01-2003
ISSN03778398
KeywordsMadagascar; Maastrichtian; Paleocene; age; paleoclimate; paleoenvironment
Abstract

Lithology, geochemistry, stable isotopes and integrated high-resolution biostratigraphy of the Berivotra and Amboanio sections provide new insights into the age, faunal turnovers, climate, sea level and environmental changes of the Maastrichtian to early Paleocene of the Mahajanga Basin of Madagascar. In the Berivotra type area, the dinosaur-rich fluvial lowland sediments of the Anembalemba Member prevailed into the earliest Maastrichtian. These are overlain by marginal marine and near-shore clastics that deepen upwards to hemipelagic middle neritic marls by 69.6 Ma, accompanied by arid to seasonally cool temperate climates through the early and late Maastrichtian. An unconformity between the Berivotra Formation and Betsiboka limestone marks the K–T boundary, and juxtaposes early Danian (zone Plc? or Pld) and latest Maastrichtian (zones CF2–CF1, Micula prinsii) sediments. Seasonally humid warm climates began near the end of the Maastrichtian and prevailed into the early Danian, accompanied by increased volcanic activity. During the late Danian (zones P1d–P2), a change to seasonally arid climates was accompanied by deepening from middle to outer neritic depths.  PDF

URLhttp://linkinghub.elsevier.com/retrieve/pii/S0377839802000944
DOI10.1016/S0377-8398(02)00094-4
Short TitleMarine Micropaleontology

Multiple impacts across the Cretaceous–Tertiary boundary

TitleMultiple impacts across the Cretaceous–Tertiary boundary
Publication TypeJournal Article
Year of Publication2003
AuthorsKeller, G, Stinnesbeck, W, Adatte, T, üben, D
JournalEarth-Science Reviews
Volume62
Issue3-4
Pagination327 - 363
Date PublishedJan-09-2003
ISSN00128252
KeywordsMultiple impacts; Maastrichtian–Danian; Microtektites; Microkrystites; Ir; PGE anomalies
Abstract

The stratigraphy and age of altered impact glass (microtektites, microkrystites) ejecta layers from the Chicxulub crater are documented in Late Maastrichtian and Early Danian sediments in Mexico, Guatemala, Belize and Haiti. In northeastern Mexico, two to four ejecta layers are present in zone CF1, which spans the last 300 ky of the Maastrichtian. The oldest ejecta layer is dated at 65.27F0.03 Ma based on sediment accumulation rates and extrapolated magnetostratigraphy. All younger ejecta layers from the Maastrichtian and Early Danian Parvularugoglobigerina eugubina zone Pla(l) may represent repeated episodes of reworking of the oldest layer at times of sea level changes and tectonic activity. The K/T boundary impact event (65.0 Ma) is not well represented in this area due to widespread erosion. An Early Danian Pla(l) Ir anomaly is present in five localities (Bochil, Actela, Coxquihui, Trinitaria and Haiti) and is tentatively identified as a third impact event at about 64.9 Ma. A multiimpact scenario is most consistent with the impact ejecta evidence. The first impact is associated with major Deccan volcanism and likely contributed to the rapid global warming of 3–4 °C in intermediate waters between 65.4 and 65.2 Ma, decrease in primary productivity and onset of terminal decline in planktic foraminiferal populations. The K/T boundary impact marks a major drop in primary productivity and the extinction of all tropical and subtropical species. The Early Danian impact may have contributed to the delayed recovery in productivity and evolutionary diversity. PDF

URLhttp://linkinghub.elsevier.com/retrieve/pii/S0012825202001629
DOI10.1016/S0012-8252(02)00162-9
Short TitleEarth-Science Reviews

Spherule deposits in Cretaceous-Tertiary boundary sediments in Belize and Guatemala

TitleSpherule deposits in Cretaceous-Tertiary boundary sediments in Belize and Guatemala
Publication TypeJournal Article
Year of Publication2003
AuthorsKeller, G, Stinnesbeck, W, Adatte, T, Holland, B, Stüben, D, Harting, M, Leon, Cd., Cruz, Jd.
JournalJournal of the Geological Society
Volume160
Issue5
Pagination783 - 795
Date PublishedJan-09-2003
ISSN0016-7649
Abstract

Large spheroid deposits at Albion Island and Armenia in northern and central Belize and the spherule deposits of southern Belize and eastern Guatemala have the same glass origin based on the presence of almost pure Cheto smectite derived from alteration of impact glass from the Chicxulub impact on Yucatan, Mexico. The same origin has also been determined for altered glass spherules in Mexico, Haiti and the Caribbean. However, the spherule layers have variable ages as a result of erosion and redeposition, with an early Danian (Parvularugoglobigerina eugubina) zone Pla(1) age in southern Belize, Guatemala, Haiti, southern Mexico and the Caribbean, and a pre-K–T (Plummerita hantkeninoides) zone CF1 age of 65.27 ± 0.03 Ma in NE Mexico. A pre-K–T age for the Chicxulub impact has now also been determined from the new Yaxcopoil 1 core drilled in the impact crater. These data show that Chicxulub was not the K–T impact that caused the end-Cretaceous mass extinction, but an earlier impact event. A multiple impact hypothesis, volcanism and climate change appears the likely scenario for the end-Cretaceous mass extinction.  PDF

URLhttp://jgs.lyellcollection.org/cgi/doi/10.1144/0016-764902-119http://jgs.geoscienceworld.org/cgi/doi/10.1144/0016-764902-119
DOI10.1144/0016-764902-119
Short TitleJournal of the Geological Society

Planktonic foraminiferal response to the latest Maastrichtian abrupt warm event: a case study from South Atlantic DSDP Site 525A

TitlePlanktonic foraminiferal response to the latest Maastrichtian abrupt warm event: a case study from South Atlantic DSDP Site 525A
Publication TypeJournal Article
Year of Publication2003
AuthorsAbramovich, S, Keller, G
JournalMarine Micropaleontology
Volume48
Issue3-4
Pagination225 - 249
Date PublishedJan-07-2003
ISSN03778398
Abstract

An abrupt global warming of 3-4°C occurred near the end of the Maastrichtian at 65.45-65.10 Ma. The environmental effects of this warm event are here documented based on stable isotopes and quantitative analysis of planktonic foraminifera at the South Atlantic DSDP Site 525A. Stable isotopes of individual species mark a rapid increase in temperature and a reduction in the vertical water mass stratification that is accompanied by a decrease in niche habitats, reduced species diversity and/or abundance, smaller species morphologies or dwarfing, and reduced photosymbiotic activity. During the warm event, the relative abundance of a large number of species decreased, including tropical^subtropical affiliated species, whereas typical mid-latitude species retained high abundances. This indicates that climate warming did not create favorable conditions for all tropical^subtropical species at mid-latitudes and did not cause a massive retreat in the local mid-latitude population. A noticeable exception is the ecological generalist Heterohelix dentata Stenestad that dominated during the cool intervals, but significantly decreased during the warm event. However, dwarfing is the most striking response to the abrupt warming and occurred in various species of different morphologies and lineages (e.g. biserial, trochospiral, keeled globotruncanids). Dwarfing is a typical reaction to environmental stress conditions and was likely the result of increased reproduction rates. Similarly, photosymbiotic activity appears to have been reduced significantly during the maximum warming, as indicated by decreased δ13C values. The foraminiferal response to climate change is thus multifaceted resulting in decreased species diversity, decreased species populations, increased competition due to reduced niche habitats, dwarfing and reduced photosymbiotic activity.  PDF

URLhttp://linkinghub.elsevier.com/retrieve/pii/S0377839803000215
DOI10.1016/S0377-8398(03)00021-5
Short TitleMarine Micropaleontology

Characterization of late Campanian and Maastrichtian planktonic foraminiferal depth habitats and vital activities based on stable isotopes

TitleCharacterization of late Campanian and Maastrichtian planktonic foraminiferal depth habitats and vital activities based on stable isotopes
Publication TypeJournal Article
Year of Publication2003
AuthorsAbramovich, S, Keller, G, üben, D, BERNER, ZSOLT
JournalPalaeogeography, Palaeoclimatology, Palaeoecology
Volume202
Issue1-2
Pagination1 - 29
Date PublishedJan-12-2003
ISSN00310182
Abstract

Depth habitats of 56 late Cretaceous planktonic foraminiferal species from cool and warm climate modes were determined based on stable isotope analyses of deep-sea samples from the equatorial Pacific DSDP Sites 577A and 463, and South Atlantic DSDP Site 525A. The following conclusions can be reached: Planoglobulina multicamerata (De Klasz) and Heterohelix rajagopalani (Govindan) occupied the deepest plankton habitats, followed by Abathomphalus mayaroensis (Bolli), Globotruncanella havanensis (Voorwijk), Gublerina cuvillieri Kikoine, and Laeviheterohelix glabrans (Cushman) also at subthermocline depth. Most keeled globotruncanids, and possibly Globigerinelliodes and Racemiguembelina species, lived at or within the thermocline layer. Heterohelix globulosa (Ehrenberg) and Rugoglobigerina, Pseudotextularia and Planoglobulina occupied the subsurface depth of the mixed layer, and Pseudoguembelina species inhabited the surface mixed layer. However, depth ranking of some species varied depending on warm or cool climate modes, and late Campanian or Maastrichtian age. For example, most keeled globotruncanids occupied similar shallow subsurface habitats as Rugoglobigerina during the warm late Campanian, but occupied the deeper thermocline layer during cool climatic intervals. Two distinct types of ‘vital effect’ mechanisms reflecting photosymbiosis and respiration effects can be recognized by the exceptional N13C signals of some species. (1) Photosymbiosis is implied by the repetitive pattern of relatively enriched N13C values of Racemiguembelina (strongest), Planoglobulina, Rosita and Rugoglobigerina species, Pseudoguembelina excolata (weakest). (2) Enriched respiration 12C products are recognized in A. mayaroensis, Gublerina acuta De Klasz, and Heterohelix planata (Cushman). Isotopic trends between samples suggest that photosymbiotic activities varied between localities or during different climate modes, and may have ceased under certain environmental conditions. The appearance of most photosymbiotic species in the late Maastrichtian suggests oligotrophic conditions associated with increased water-mass stratification.  PDF

URLhttp://linkinghub.elsevier.com/retrieve/pii/S0031018203005728
DOI10.1016/S0031-0182(03)00572-8
Short TitlePalaeogeography, Palaeoclimatology, Palaeoecology

Guembelitria-dominated late Maastrichtian planktic foraminiferal assemblages mimic early Danian in central Egypt

TitleGuembelitria-dominated late Maastrichtian planktic foraminiferal assemblages mimic early Danian in central Egypt
Publication TypeJournal Article
Year of Publication2002
AuthorsKeller, G
JournalMarine Micropaleontology
Volume47
Issue1-2
Pagination71 - 99
Date PublishedJan-01-2003
ISSN03778398
Abstract

During the late Maastrichtian (66.8-65.5 Ma) the Asyut Basin in central Egypt experienced a breakdown of the surface to bottom gradient of the 13C/12C ratio with planktic N13C values 0.2-0.8x lighter than benthic values. Planktic foraminiferal species diversity was reduced by more than 50%, with assemblages dominated (60-90%) by the opportunistic blooms of the disaster species Guembelitria cretacea, which mimic the early Danian. The prolonged breakdown in productivity occurred during a time of tectonic activity and increased terrestrial runoff that may have resulted in highly eutrophic waters, coupled with a sea-level regression (65.5 Ma) that led to restricted circulation. Increased productivity during the short climate warming between 65.4 and 65.2 Ma is associated with increased species diversity, abundant rugoglobigerinids and common heterohelicids. At the end of the Maastrichtian, decreased productivity coincided with the K/T impact and mass extinction, followed by characteristically early Danian low diversity assemblages. The similarity of the late Maastrichtian and post-K/T impact Guembelitria-dominated assemblages reveals that the planktic foraminiferal response to the K/T catastrophe was not unique, but followed a predictable pattern of response to severe environmental perturbations.  PDF

URLhttp://linkinghub.elsevier.com/retrieve/pii/S0377839802001160
DOI10.1016/S0377-8398(02)00116-0
Short TitleMarine Micropaleontology

High-stress paleoenvironment during the late Maastrichtian to early Paleocene in Central Egypt

TitleHigh-stress paleoenvironment during the late Maastrichtian to early Paleocene in Central Egypt
Publication TypeJournal Article
Year of Publication2002
AuthorsKeller, G, Adatte, T, Burns, SJ, Tantawy, AAziz
JournalPalaeogeography, Palaeoclimatology, Palaeoecology
Volume187
Issue1-2
Pagination35 - 60
Date PublishedJan-11-2002
ISSN00310182
Keywordshigh-stress late Maastrichtian paleoenvironment
Abstract

Biostratigraphic, mineralogical, geochemical and isotopic analyses of the Gebel Qreiya section in the Asyut Basin of central Egypt indicate a depositional environment interrupted by periods of erosion due to local tectonic activity exacerbated by eustatic sea-level fluctuations, and by high-stress environmental conditions akin to those normally experienced during the Cretaceous-Tertiary boundary transition. During the late Maastrichtian (66.8-65.4 Ma) this region experienced a breakdown of the biologically mediated surface to bottom gradient of the 13C/12C ratio with planktic N13C values 0.2-0.8x lighter than benthic values. Planktic foraminiferal species diversity was reduced by more than 50%, with faunal assemblages dominated (75-90%) by the opportunistic disaster species Guembelitria cretacea, which alternate with abundance of small, low oxygen-tolerant heterohelicids (Heterohelix navarroensis, H. dentata, H. globulosa). This prolonged breakdown in ocean primary productivity occurred during a time of global climate cooling and sea-level regressions (at 66.8 and 65.5 Ma), though clay mineralogy suggests that locally low seasonality warm, wet, tropical and subtropical conditions prevailed. The high detrital influx suggests that the biologically high-stress environment was primarily linked to the existing shallow shelf conditions in southern Egypt, and possibly to local tectonic activity and restricted circulation. A normal carbon isotope gradient was briefly reestablished during the short climate warming and rising sea level between 65.4 and 65.2 Ma, a time of increased species diversity, peak abundance of rugoglobigerinids and common heterohelicids. During the last 200 000 years of the Maastrichtian, increased precipitation and terrestrial runoff (increased phyllosilicates and kaolinite) and increasing total organic carbon values are associated with Heterohelix-dominated planktic foraminiferal assemblages. The K/T boundary is marked by a red clay layer and Ir anomaly of 5.4 ppb. During the early Danian, planktic foraminiferal populations and stable isotope data indicate that similarly fluctuating high-stress conditions prevailed in central Egypt as elsewhere in the marginal eastern Tethys.  PDF

URLhttp://linkinghub.elsevier.com/retrieve/pii/S0031018202005047
DOI10.1016/S0031-0182(02)00504-7
Short TitlePalaeogeography, Palaeoclimatology, Palaeoecology

Special Paper 356: Multiple spherule layers in the late Maastrichtian of northeastern Mexico

TitleSpecial Paper 356: Multiple spherule layers in the late Maastrichtian of northeastern Mexico
Publication TypeBook
Year of Publication2002
AuthorsKeller, G, Adatte, T, Stinnesbeck, W, Affolter, M, Schilli, L, Lopez-Oliva, JGuadalupe
Volume356
Number of Pages145 - 161
PublisherGeological Society of America
Abstract

The discovery of as many as 4 spherule layers within 10 m of pelagic marls below the sandstone-siltstone complex and Cretaceous-Tertiary (K-T) boundary in the La Sierrita area of northeastern Mexico reveals a more complex K-T scenario than previously imagined. These spherule layers were deposited within pelagic marls of the Mendez Formation; the oldest layer is as much as 10 m below the K-T boundary. The marls are of latest Maastrichtian calcareous nannofossil Micula prinsii zone and planktic foraminiferal zone CF1 (Plummerita hantkeninoides) age; the latter spans the last 300 k.y. of the Maastrichtian. The oldest spherule layer was deposited near the base of zone CF1 and marks the original spherule-producing event. This is indicated by the presence of a few marl clasts and benthic foraminifera that are frequently surrounded by welded glass, and many welded spherules with schlieren features, indicating that deposition occurred while the glass was still hot and ductile. It is possible that some, or all, of the three stratigraphically younger spherule layers have been reworked from the original spherule deposit, as suggested by the common marl clasts, terrigenous input, reworked benthic and planktic foraminifera, and clusters of agglutinated spherules. These data indicate that at least one spherule-producing event occurred during the late Maastrichtian and provide strong evidence for multiple catastrophic events across the K-T transition.  PDF

URLhttp://www.gsajournals.org/perlserv/?request=get-specialpub-toc&isbn=0-8137-2356-6http://specialpapers.gsapubs.org/cgi/doi/10.1130/0-8137-2356-6.145
DOI10.1130/0-8137-2356-610.1130/0-8137-2356-6.145

Paleoecology of the Cretaceous–Tertiary mass extinction in planktonic foraminifera

TitlePaleoecology of the Cretaceous–Tertiary mass extinction in planktonic foraminifera
Publication TypeJournal Article
Year of Publication2002
AuthorsKeller, G, Adatte, T, Stinnesbeck, W, Luciani, V, Karoui-Yaakoub, N, Zaghbib-Turki, D
JournalPalaeogeography, Palaeoclimatology, Palaeoecology
Volume178
Issue3-4
Pagination257 - 297
Date PublishedJan-02-2002
ISSN00310182
KeywordsTunisia; paleoecology; K-T planktonic foraminifera
Abstract

Paleobiogeographic patterns of the Cretaceous^Tertiary (K-T) mass extinction in planktonic foraminifera in Tunisia, spanning environments from open marine upper bathyal, to shelf and shallow marginal settings, indicate a surprisingly selective and environmentally mediated mass extinction. This selectivity is apparent in all of the environmental proxies used to evaluate the mass extinction, including species richness, ecological generalists, ecological specialists, surface and subsurface dwellers, whether based on the number of species or the relative percent abundances of species. The following conclusions can be reached for shallow to deep environments: about three quarters of the species disappeared at or near the K-T boundary and only ecological generalists able to tolerate wide variations in temperature, nutrients, salinity and oxygen survived. Among the ecological generalists (heterohelicids, guembelitrids, hedbergellids and globigerinellids), only surface dwellers survived. Ecological generalists which largely consisted of two morphogroups of opportunistic biserial and triserial species also suffered selectively. Biserials thrived during the latest Maastrichtian in well stratified open marine settings and dramatically declined in relative abundances in the early Danian. Triserials thrived only in shallow marginal marine environments, or similarly stressed ecosystems, during the latest Maastrichtian, but dominated both open marine and restricted marginal settings in the early Danian. This highly selective mass extinction pattern reflects dramatic changes in temperature, salinity, oxygen and nutrients across the K-T boundary in the low latitude Tethys ocean which appear to be the result of both long-term environmental changes (e.g., climate, sea level, volcanism) and short-term effects (bolide impact). PDF

URLhttp://linkinghub.elsevier.com/retrieve/pii/S0031018201003996
DOI10.1016/S0031-0182(01)00399-6
Short TitlePalaeogeography, Palaeoclimatology, Palaeoecology

Trace elements, stable isotopes, and clay mineralogy of the Elles II K–T boundary section in Tunisia: indications for sea level fluctuations and primary productivity

TitleTrace elements, stable isotopes, and clay mineralogy of the Elles II K–T boundary section in Tunisia: indications for sea level fluctuations and primary productivity
Publication TypeJournal Article
Year of Publication2002
AuthorsStüben, D, Kramar, U, Berner, Z, Stinnesbeck, W, Keller, G, Adatte, T
JournalPalaeogeography, Palaeoclimatology, Palaeoecology
Volume178
Issue3-4
Pagination321 - 345
Date PublishedJan-02-2002
ISSN00310182
Abstract

Trace elements and stable isotopes in bulk rocks and foraminifera, bulk rock and clay mineral compositions, are used as palaeoproxies to evaluate sea level fluctuations, climatic changes and variations in primary productivity across the K-T transition at Elles II in Tunisia from 1 m (~33 kyr) below to 1 m (~70 kyr) above the K-T boundary. Results on clay minerals, major and trace elements, stable isotopes in bulk rock samples (e.g. Ca, Cu, Zn, Rb, Sr, Zr, Ba, δ13C and δ18O), and in foraminifera (Sr/Ca, N13C, N18O) indicate that the latest Maastrichtian (last~33 kyr) in Tunisia was marked by a relatively warm, but humid climate and a rising sea level. The transgressive surface is marked by deposition of a foraminiferal packstone just below the K-T boundary followed by maximum flooding across the K-T boundary (red layer and black clay layer). Humid warm conditions accompanied the maximum flooding, along with increased total organic carbon values and rapidly decreasing primary productivity. At the K-T boundary, an impact event (Ir anomaly, Ni-rich spinels, spherules) exacerbated already stressed environmental conditions leading to the mass extinction of tropical planktic foraminifera. Increasingly more humid conditions prevailed within the lowermost Danian Zone P0 (~50 kyr) culminating in a sea level lowstand near the top of P0. A slow recovery of the ecosystem in Zone P1a coincided with a rising sea level and gradually less humid climatic conditions.  PDF

URLhttp://linkinghub.elsevier.com/retrieve/pii/S0031018201004011
DOI10.1016/S0031-0182(01)00401-1
Short TitlePalaeogeography, Palaeoclimatology, Palaeoecology

High stress late Maastrichtian paleoenvironment: inference from planktonic foraminifera in Tunisia

TitleHigh stress late Maastrichtian paleoenvironment: inference from planktonic foraminifera in Tunisia
Publication TypeJournal Article
Year of Publication2002
AuthorsAbramovich, S, Keller, G
JournalPalaeogeography, Palaeoclimatology, Palaeoecology
Volume178
Issue3-4
Pagination145 - 164
Date PublishedJan-02-2002
ISSN00310182
Abstract

High resolution (~5-10 kyr) planktonic foraminiferal analysis at Elles, Tunisia, reveals major changes in the structure of the Tethyan marine ecosystem during the upper Maastrichtian. During the first 1.5 Myr of the late Maastrichtian (68.3-66.8 Ma) relatively stable environmental conditions and cool temperatures are indicated by diverse planktonic foraminiferal populations with abundant intermediate and surface dwellers. A progressive cooling trend between ~66.8-65.45 Ma resulted in the decline of globotruncanid species (intermediate dwellers). This group experienced a further decline at the climax of a rapid warm event about 300 kyr before the K-T boundary. At the same time relative abundances of long ranging dominant species fluctuated considerably reflecting the high stress environmental conditions. Times of critical high stress environments during the late Maastrichtian, and particularly at the K-T boundary, are indicated by low species diversity and blooms of the opportunistic genus Guembelitria at warm-cool transition intervals. During the last 100 kyr of the Maastrichtian rapid cooling is associated with accelerated species extinctions followed by the extinction of all tropical and subtropical species at the K-T boundary.  PDF

URLhttp://linkinghub.elsevier.com/retrieve/pii/S0031018201003947
DOI10.1016/S0031-0182(01)00394-7
Short TitlePalaeogeography, Palaeoclimatology, Palaeoecology

Special Paper 356: Two anomalies of platinum group elements above the Cretaceous-Tertiary boundary at Beloc, Haiti: Geochemical context and consequences for the impact scenario

TitleSpecial Paper 356: Two anomalies of platinum group elements above the Cretaceous-Tertiary boundary at Beloc, Haiti: Geochemical context and consequences for the impact scenario
Publication TypeBook
Year of Publication2002
AuthorsStüben, D, Kramar, U, BERNER, ZSOLT, Eckhardt, J-D, Stinnesbeck, W, Keller, G, Adatte, T, Heide, K
Volume356
Number of Pages163 - 188
PublisherGeological Society of America
Abstract

A detailed geochemical investigation of an expanded Cretaceous-Tertiary (K-T) boundary section near Beloc (B3), Haiti, reveals a complex pattern of sedimentation of multiple origins as a result of erosional, biogenic, volcanic, and impact events. Carbonate-rich uppermost Maastrichtian sediments with high excess rates for Cu, Zn, and Sr (biogenic origin) indicate high productivity (δ13C) and warm temperatures (δ18O). These sediments are overlain by Paleocene (early Danian zone P1a) spherulerich clayey layers that indicate lower productivity, lower temperatures, and high input of glass and biogenic carbonate. Reworked Maastrichtian sediments are mixed with spherule-rich layers. This spherule-rich deposit is topped by a thin layer rich in Fe that also contains an Ir-dominated anomaly of platinum group elements (PGE) with an almost chondritic abundance pattern, which appears to be the result of a cosmic influx. Monotonous limestones above this interval reflect recovery to normal pelagic sedimentation, which is interrupted by a second PGE anomaly in an Fe-rich clayey layer in the middle part of zone P1a. All PGEs are enriched in this interval and the PGE pattern is basalt like, suggesting a volcanic source. Both PGE anomaly horizons coincide with productivity and temperature changes.  PDF

URLhttp://www.gsajournals.org/perlserv/?request=get-specialpub-toc&isbn=0-8137-2356-6http://specialpapers.gsapubs.org/cgi/doi/10.1130/0-8137-2356-6.163
DOI10.1130/0-8137-2356-610.1130/0-8137-2356-6.163

Late Cretaceous to early Paleocene climate and sea-level fluctuations: the Tunisian record

TitleLate Cretaceous to early Paleocene climate and sea-level fluctuations: the Tunisian record
Publication TypeJournal Article
Year of Publication2002
AuthorsThierry, A, Keller, G, Stinnesbeck, W
JournalPalaeogeography, Palaeoclimatology, Palaeoecology
Volume2754
Start Page1
Keywordsbulk, clay minerals, climate fluctuations, geochemistry, K-T boundary, Maastrichtian, organic matter, sea-level, Tunisia, Upper Campanian
Abstract

Climate and sea-level fluctuations across the Cretaceous-Tertiary (K-T) transition in Tunisia were examined based on bulk rock and clay mineralogies, biostratigraphy and lithology in five sections (El Melah, El Kef, Elles, Ain Settara and Seldja) spanning from open marine to shallow inner neritic environments. Late Campanian to early Danian trends examined at El Kef and Elles indicate an increasingly more humid climate associated with sea-level fluctuations and increased detrital influx that culminates at the K-T transition. This long-term trend in increasing humidity and runoff in the Tethys region is associated with middle and high latitude cooling. Results of short-term changes across the K-T transition indicate a sea-level lowstand in the latest Maastrichtian about 25^100 ka below the K-T boundary with the regression marked by increased detrital influx at El Kef and Elles and a short hiatus at Ain Settara. A rising sea-level at the end of the Maastrichtian is expressed at Elles and El Kef by deposition of a foraminiferal packstone. A flooding surface and condensed sedimentation mark the K^T boundary clay which is rich in terrestrial organic matter. The P0- P1a transition is marked by a sea-level lowstand corresponding to a short hiatus at Ain Settara where most of P0 is missing and a period of non-deposition and erosion in the lower part of P1a (64.95 Ma). At Seldja, P0 and possibly the topmost part of CF1 are missing. These sea-level fluctuations are associated with maximum humidity. These data suggest that in Tunisia, long-term environmental stresses during the last 500 ka before the K-T boundary and continuing into the early Danian are primarily related to climate and sea-level fluctuations. Within this long-term climatic trend the pronounced warm and humid event within the latest Maastrichtian Zone CF1 may be linked to greenhouse conditions induced by Deccan volcanism. The absence of any significant clay mineral variations at or near the K-T boundary and Ir anomaly suggests that the bolide impact had a relatively incidental short-term effect on climate in the Tethys region.   PDF

Paleoenvironment across the Cretaceous-Tertiary transition in eastern Bulgaria

TitlePaleoenvironment across the Cretaceous-Tertiary transition in eastern Bulgaria
Publication TypeBook Chapter
Year of Publication2002
AuthorsAdatte, T, Keller, G, Burns, S, Stoykova, KH, Ivanov, MI, Vangelov, D, Kramar, U, Stüben, D
Book TitleCatastrophic Events and Mass Extinctions: Impacts and Beyond: Boulder, Colorado
PublisherGeological Society of America Special Paper 356
CityBoulder
Abstract

The Cretaceous-Tertiary (K-T) transition in eastern Bulgaria (Bjala) was analyzed in terms of lithology, mineralogy, stable isotopes, trace elements, and planktic foraminifera. The sequence represents a boreal-Tethyan transitional setting, spans from the last 300 k.y. of the Maastrichtian (zone CF1) through the early Danian (zones P0-Plc), and contains several short hiatuses. It differs from low-latitude Tethyan sequences primarily by lower diversity assemblages, pre-K-T faunal changes, a reduced K-T δ13C shift, and the presence of two clay layers with platinum group element anomalies. The first clay layer marks the K-T boundary impact event, as indicated by an iridium anomaly (6.1 ppb), the mass extinction of tropical and subtropical planktic foraminifera, and cooling. The second clay layer is stratigraphically within the upper Parvularugoglobigerina eugubina (Pla) zone and contains a small Ir enrichment (0.22 ppb), a major Pd enrichment (1.34 ppb), and anomalies in Ru (0.30 ppb) and Rh (0.13 ppb) that suggest a volcanic source.  PDF

Slumping and a sandbar deposit at the Cretaceous-Tertiary boundary in the El Tecolote section (northeastern Mexico): An impact-induced sediment gravity flow

TitleSlumping and a sandbar deposit at the Cretaceous-Tertiary boundary in the El Tecolote section (northeastern Mexico): An impact-induced sediment gravity flow
Publication TypeJournal Article
Year of Publication2001
AuthorsSoria, AR, Liesa, CL, Mata, MPilar, Arz, JA, Alegret, L, Arenillas, I, Meléndez, A
JournalGeology
Volume29
Pagination231-234
Abstract

Slumps affecting uppermost Méndez Formation marls, as well as the spherulitic layer and basal part of the sandy deposits of the Cretaceous-Tertiary (K-T) boundary clastic unit, are described at the new K-T El Tecolote section (northeastern Mexico). These K-T clastic deposits represent sedimentation at middle-bathyal water depths in channel and nonchannel or levee areas of reworked materials coming from environments ranging from outer shelf to shallower slope via a unidirectional, high- to low-density turbidite flow. We emphasize the development and accretion of a lateral bar in a channel area from a surging low-density turbidity current and under a high-flow regime. The slumps discovered on land and the sedimentary processes of the K-T clastic unit reflect destabilization and collapse of the continental margin, support the mechanism of gravity flows in the deep sea, and represent important and extensive evidence for the impact effects in the Gulf of México triggered by the Chicxulub event.  PDF

URLhttp://geology.gsapubs.org/content/29/3/231.abstract
DOI10.1130/0091-7613(2001)029<0231:SAASDA>2.0.CO;2

Are Ir anomalies sufficient and unique indicators for cosmic events?

TitleAre Ir anomalies sufficient and unique indicators for cosmic events?
Publication TypeJournal Article
Year of Publication2001
AuthorsKramar, U, üben, D, Berner, Z, Stinnesbeck, W, Philipp, H, Keller, G
JournalPlanetary and Space Science
Volume49
Issue8
Pagination831 - 837
Date PublishedJan-07-2001
ISSN00320633
Abstract

Ir anomalies are often considered unique indicators for cosmic events. The present paper compares the contents and patterns of platinum group element (PGE) anomalies of magmatic and sedimentary origins with similar anomalies found in the Cretaceous–Tertiary (K/T) boundary impact clay and other PGE enriched layers across the K/T boundary and early Danian (Parvularugoglobigerina eugubina zone) at Beloc, Haiti. This analysis demonstrates that PGE patterns provide more conclusive evidence for the reconstruction of paleoevents than that can be achieved by Ir content alone.  PDF

URLhttp://linkinghub.elsevier.com/retrieve/pii/S0032063301000368
DOI10.1016/S0032-0633(01)00036-8
Short TitlePlanetary and Space Science

Palaeoenvironment of the Cenomanian–Turonian transition at Eastbourne, England

TitlePalaeoenvironment of the Cenomanian–Turonian transition at Eastbourne, England
Publication TypeJournal Article
Year of Publication2001
AuthorsKeller, G, Han, Q, Adatte, T, Burns, SJ
JournalCretaceous Research
Volume22
Issue4
Pagination391 - 422
Date PublishedJan-08-2001
ISSN01956671
KeywordsCenomanian–Turonian; Eastbourne; planktic foraminifera; stable isotopes; sea-level changes
Abstract

Lithology, stable isotopes and planktic foraminiferal analyses of the Eastbourne section at Gun Gardens (southeast England) reflect sea-level fluctuations and changing climatic and oceanographic conditions across the Cenomanian–Turonian transition. The δ13C excursion began with a 1.8‰ positive shift in Plenus Marls Beds 1–3 (R. cushmani Zone), a trough in Bed 4, a second δ13C shift of 0.8‰ in Bed 7 and a gradually decreasing plateau during deposition of the Ballard Cliff Member. Lithological variations, sharp erosion surfaces, bioturbation and increased detrital influx indicate that sea-level fluctuations, cooling and a marine regression accompanied the δ13C excursion within the Plenus Marls, followed by warming and a major marine transgression in the upper part of the Plenus Marls and Ballard Cliff Member. Two faunal turnover phases coincided with the two-phased δ13C excursion. Phase I in Bed 3 is marked by the extinction of the deeper dwelling planktic foraminifer Rotalipora, the origination of the thermocline dweller Dicarinella, dominance of the low oxygen tolerant Heterohelix species, and common surface dwellers Guembelitria and Whiteinella. This faunal turnover reflects a lower sea level, enhanced productivity and temporary expansion of the oxygen minimum zone associated with climate cooling and increased upwelling. Phase II near the top of the Plenus Marls (Beds 7–8) is marked by the temporary disappearance of about 50% of the species, increased abundance of surface dwellers and a shift to dominance of low-oxygen tolerant Heterohelix species globally. This faunal turnover may reflect increased primary productivity and a long-term expansion of the oxygen minimum zone associated with climate warming and a marine transgression. Faunal turnover phase II stratigraphically correlates with the global oceanic anoxic event in Italy (Bonarelli Level) and Tunisia (Bahloul Formation), whereas phase I correlates with the onset of organic-rich facies in the upper R. cushmani Zone of these regions. High resolution biostratigraphic correlation is based on planktic foraminifera and the subdivision of Whiteinella archeocretacea Zone into three subzones.  PDF

URLhttp://linkinghub.elsevier.com/retrieve/pii/S0195667101902642
DOI10.1006/cres.2001.0264
Short TitleCretaceous Research

Maastrichtian to Paleocene depositional environment of the Dakhla Formation, Western Desert, Egypt: sedimentology, mineralogy, and integrated micro- and macrofossil biostratigraphies

TitleMaastrichtian to Paleocene depositional environment of the Dakhla Formation, Western Desert, Egypt: sedimentology, mineralogy, and integrated micro- and macrofossil biostratigraphies
Publication TypeJournal Article
Year of Publication2001
AuthorsTantawy, AA, Keller, G, Adatte, T, Stinnesbeck, W, Kassab, A, Schulte, P
JournalCretaceous Research
Volume22
Issue6
Pagination795 - 827
Date PublishedJan-12-2001
ISSN01956671
Abstract

Integrated sedimentology, mineralogy, geochemistry, and microfossil and macrofossil biostratigraphies of the Maastrichtian– early Paleocene Dakhla Formation of the Western Desert, Egypt, provide improved age resolution, information on the cyclic nature of sediment deposition, and the reconstruction of depositional environments. Age control based on integrated biostratigraphies of planktic foraminifera, calcareous nannofossils and macrofossils yields the following ages for stratigraphic and lithologic sequences. The contact between the Duwi and Dakhla formations marks the Campanian/Maastrichtian boundary (zone CF8a/b boundary) and is dated at about 71 Ma. The age of the Dakhla Formation is estimated to span from 71 Ma at the base to about 63 Ma at the top (zones CF8a–Plc). The Cretaceous/Tertiary (K/T) boundary is within the upper unit of the Kharga Shale Member and marked by a hiatus that spans from 64.5 Ma in the lower Paleocene (base Plc) to at least 65.5 Ma (base CF2, base M. prinsii zones) in the upper Maastrichtian at Gebel Gifata, the type locality of the Dakhla Formation. As a result, the Bir Abu Minqar horizon, deposited between about 64.2 and 64.5 Ma (Plc(l) zone), directly overlies the K/T boundary hiatus. Major hiatuses also span the late Maastrichtian–early Paleocene in sections to the northwest (c. 61.2–65.5 Ma at North El Qasr, c. 61.2–69 Ma at Bir Abu Minqar and c. 61.2–65.5 Ma at Farafra), and reflect increased tectonic activity.

During the Maastrichtian–early Paleocene a shallow sea covered the Western Desert of Egypt and the clastic sediment source was derived primarily from tectonic activity of the Gilf El Kebir spur to the southwest of Dakhla and the Bahariya arch. Uplift in the region resulted in major hiatuses in the late Maastrichtian–early Paleocene with increased erosion to the southwest. The area was located near the palaeoequator and experienced warm, wet, tropical to subtropical conditions characterized by low seasonality contrasts and predominantly chemical weathering (high kaolinite and smectite). A change towards perennially more humid conditions with enhanced runoff (increased kaolinite) occurred towards the end of the Maastrichtian and in the early Paleocene with shallow seas fringed by Nypa palm mangroves. Sediment deposition was predominantly cyclic, consisting of alternating sandstone/shale cycles with unfossiliferous shales deposited during sea-level highstands in inner neritic to lagoonal environments characterized by euryhaline, dysaerobic or low oxygen conditions. Fossiliferous calcareous sandstone layers were deposited in well-oxygenated shallow waters during sea-level lowstand periods.  PDF

URLhttp://linkinghub.elsevier.com/retrieve/pii/S0195667101902915
DOI10.1006/cres.2001.0291
Short TitleCretaceous Research