MISCELLANEOUS EVENTS

5000 year sedimentary record of hurricane strikes on the central coast of Belize

Title5000 year sedimentary record of hurricane strikes on the central coast of Belize
Publication TypeJournal Article
Year of Publication2009
AuthorsMcCloskey, TA, Keller, G
JournalQuaternary International
Volume195
Pagination53–68
Date Publishedfeb
Abstract

The central coast of Belize has been subject to hurricane strikes throughout recorded history with immense human and material cost to the Belizean people. What remains unknown is the long-term frequency of hurricane strikes and the effects such storms may have had on the ancient Maya civilization. Our sedimentary study of major hurricane strikes over the past 5000 years provides preliminary insights. We calculate that over the past 500 years major hurricanes have struck the Belize coast on average once every decade. One giant hurricane with probably particularly catastrophic consequences struck Belize sometime before AD 1500. A temporal clustering of hurricanes suggests two periods of hyperactivity between ∼4500 and 2500 14C yr BP, which supports a regional model of latitudinal migration of hurricane strike zones. Our preliminary hurricane data, including the extreme apparent size of the giant event, suggest that prehistoric hurricanes were capable of having exerted significant environmental stress in Maya antiquity.   PDF

URLhttps://doi.org/10.1016/j.quaint.2008.03.003
DOI10.1016/j.quaint.2008.03.003

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

The Eocene-Oligocene planktic foraminiferal transition: extinctions, impacts and hiatuses

TitleThe Eocene-Oligocene planktic foraminiferal transition: extinctions, impacts and hiatuses
Publication TypeJournal Article
Year of Publication1993
AuthorsMolina, E, Gonzalvo, C, Keller, G
JournalGeological Magazine
Volume130
Pagination483
Date Published07/1993
Abstract

Biostratigraphic study and re-examination of 22 late Eocene to early Oligocene sections provides data in support of three and possibly a fourth late Eocene impact events in the G. index Zone during a period of about 1 Ma of the middle Priabonian between 34.7 and 35.7 Ma. No major species extinctions or significant species abundance changes directly coincide with these impact events. Species extinctions are gradual and selective, affecting primarily cool-temperature-intolerant surface dwellers. These extinctions began with the onset of global cooling during the early middle Eocene and culminated near the Eocene/Oligocene boundary. The global cooling was associated with the isolation of Antarctica as Australia moved northward, the development of a circum-Antarctic circulation, growth of Antarctic ice sheet beginning by late middle Eocene time and a change from a thermospheric to thermohaline circulation. We find no evidence that the multiple late Eocene impact events directly contributed to the climatic deterioration already in progress.  PDF

 

URLhttps://doi.org/10.1017/s0016756800020550
DOI10.1017/s0016756800020550

Late neogene history of the Pacific-Caribbean gateway

TitleLate neogene history of the Pacific-Caribbean gateway
Publication TypeJournal Article
Year of Publication1989
AuthorsKeller, G, Zenker, CE, Stone, SM
JournalJournal of South American Earth Sciences
Volume2
Pagination73–108
Date Published01/1989
Abstract

Planktic foraminiferal provinces of Caribbean DSDP Hole 502A and East Pacific DSDP Hole 503A have been analyzed and compared with benthic and planktic isotope records, carbonate, hiatus events, and sea level changes. Four major events are evident in the closure history of the Pacific-Caribbean gateway, at 6.2, 4.2, 2.4 and 1.8 Ma. The faunal change at 6.2 Ma coincides with the δ13C shift and is primarily caused by upwelling in the western Caribbean. This suggests restricted circulation of intermediate water and deflection northeastward, strengthening the Gulf Stream as reflected in the first major erosion on Blake Plateau. The second faunal change, at 4.2 Ma, coincides with increased surface water salinity evident in δ18O data and indicates increasingly restricted surface water exchange. Divergence of faunal provinces beginning at 2.4 Ma is marked by increasing abundance of high salinity tolerant species (Globigerinoides ruber) in the Caribbean. This suggests that initial closure of the Pacific-Caribbean gateway and cessation of sustained surface current flow between the Pacific and Caribbean occurred as late as 2.4 Ma. Maximum divergence of faunal provinces begins at 1.8 Ma and continues to the present. This implies that at least incipient littoral-neritic leakage occurred across the Pacific-Caribbean gateway between 2.4 and 1.8 Ma, with final closure by 1.8 Ma.  PDF

URLhttps://doi.org/10.1016/0895-9811(89)90028-x
DOI10.1016/0895-9811(89)90028-x

Paleodepth distribution of Neocene deep-sea hiatuses

TitlePaleodepth distribution of Neocene deep-sea hiatuses
Publication TypeJournal Article
Year of Publication1987
AuthorsKeller, G, BARRON, JOHNA
JournalPaleoceanography
Volume2
Pagination697–713
Date Published12/1987
Abstract

The depth of formation of Miocene to middle Pliocene deep-sea hiatuses (NH1 to NH8)has been determined using 152 Deep Sea Drilling Project sites in the Atlantic, Pacific and Indian oceans. Megahiatuses representing maxima in deep-sea erosion, occur at three water depths: below 3800 m, at intermediate depths between about 2000 and 3000 m, and in shallower waters above 1500 m paleodepth. Both the paleodepths and distribution of these hiatus maxima suggest that flow of Antarctic Bottom Water, Antarctic Intermediate Water, and North Atlantic Deep Water masses largely caused this erosion. Correlation of the hiatuses with oxygen isotope, carbonate and sea level records indicates that prior to 11 Ma, brief hiatuses including those resulting from nondeposition in high-productivity equatorial regions largely correlate with global cooling episodes, high-carbonate content, and lowstands of sea level. During the last 11 m.y., hiatuses also seem to correlate with cooling episodes, but carbonate dissolution is characteristic and sea levels may have been rising or at a lowstand. During the NH4, NH7, and NH8 intervals, it is possible that a rise in sea level corresponds with polar cooling, but there is uncertainty in correlation. Brief hiatuses during rising sea levels can be explained by basin-shelf fractionation of carbonates. Hiatuses during sea level lowstands and cooling episodes may result from intensified bottom water circulation and increased corrosiveness of bottom water due to higher levels of CO2 and increased productivity during increased upwelling.  PDF

URLhttps://doi.org/10.1029/pa002i006p00697
DOI10.1029/pa002i006p00697

Stepwise mass extinctions and impact events: Late Eocene to early Oligocene

TitleStepwise mass extinctions and impact events: Late Eocene to early Oligocene
Publication TypeJournal Article
Year of Publication1986
AuthorsKeller, G
JournalMarine Micropaleontology
Volume10
Pagination267–293
Date Publishedsep
Abstract

Species ranges and relative abundances of dominant planktonic foraminifers of eight late Eocene to early Oligocene deep-sea sections are discussed to determine the nature and magnitude of extinctions and to investigate a possible cause-effect relationship between impact events and mass extinctions.

Late Eocene extinctions are neither catastrophic nor mass extinctions, but occur stepwise over a period of about 1–2 million years. Four stepwise extinctions are identified at the middle/late Eocene boundary, the upperGlobigerapsis semiinvoluta zone, theG. semiinvoluta/Globorotalia cerroazulensis zone boundary and at the Eocene/Oligocene boundary. Each stepwise extinction event represents a time of accelerated faunal turnover characterized by generally less than 15% species extinct and in itself is not a significant extinction event. Relative species abundance changes at each stepwise extinction event, however, indicate a turnover involving > 60% of the population implying major environmental changes.

There microtektite horizons are present in late Eocene sediments; one in the upperG. semiinvoluta zone (38.2 Ma) and two closely spaced layers only a few thousand years apart in the lower part of theGloborotalia cerroazulensis zone (37.2 Ma). Each of the three impact events appears to have had some effect on microplankton communities. However, the overriding factor that led to the stepwise mass extinctions may have been the result of multiple causes as there is no evidence of impacts associated with the step preceding, or the step following the deposition of the presently known microtektite horizons.   PDF

URLhttps://doi.org/10.1016/0377-8398(86)90032-0
DOI10.1016/0377-8398(86)90032-0

Late Eocene Impact Events and Stepwise Mass Extinctions

TitleLate Eocene Impact Events and Stepwise Mass Extinctions
Publication TypeBook Chapter
Year of Publication1986
AuthorsKeller, G
Book TitleDevelopments in Palaeontology and Stratigraphy
Pagination403–412
PublisherElsevier
Abstract

Late Eocene extinctions are neither catastrophic nor mass extinctions, but occur stepwise in a sequence of four steps over a period of 3.4 million years. Closely associated with two of the stepwise extinction events are three microtektite horizons; one in the upper part of Globigerapsis semiinvoluta Zone at 38.2 Ma, and two closely spaced layers in the lower part of Globorotalia cerroazulensis Zone at 37.3 and 37.2 Ma. Species extinctions and relative species abundance declines are closely associated with microtektite layers and suggest, but do not prove, a cause-effect relationship between impact events and some of the stepwise mass extinctions.

URLhttps://doi.org/10.1016/s0920-5446(08)70144-4
DOI10.1016/s0920-5446(08)70144-4

The evolution of Miocene surface and near-surface marine temperatures: Oxygen isotopic evidence

TitleThe evolution of Miocene surface and near-surface marine temperatures: Oxygen isotopic evidence
Publication TypeBook Chapter
Year of Publication1985
AuthorsSavin, SM, Abel, L, Barrera, E, Hodell, D, Kennett, JP, Murphy, M, Keller, G, Killingley, J, Vincent, E
Book TitleGeological Society of America Memoirs
Pagination49–82
PublisherGeological Society of America
Abstract

Oxygen isotopic analyses of planktonic foraminifera have provided a picture ofmany aspects of the evolution of the temperature structure of surface and near-surfaceoceans during the Miocene. In time slice studies oceanographic conditions have beeninterpreted from synoptic maps of isotopic data at between 22 and 27 locations in theAtlantic, Pacific and Indian Oceans. Three time slice intervals were examined: 22 Ma(foraminifera! zone N4B) and 16 Ma (N8) in early Miocene time; and 8 Ma (N17) in lateMiocene time. In time series studies, the evolution of oceanographic conditions at singlelocalities during an extended period of time were inferred from 18O values of planktonicforaminifera.Surface waters warmed throughout the early Miocene at almost all localities examined.At 22 Ma, the Pacific Ocean was characterized by relatively uniform temperaturesin the equatorial region but a marked east-west asymmetry in the tropical South Pacific,with higher temperatures in the west. Between 22 Ma and 16 Ma, tropical Pacificsurface waters warmed, but wanned more in the east than the west. At 16 Ma, theasymmetric distribution of temperatures in the South Pacific Ocean remained, and thelatitudinal temperature gradient, inferred from the isotopic data, was gentler than that ofeither the late Miocene or Modern ocean.Between the late early Miocene and late Miocene, surface waters at most lowlatitudePacific sites warmed while those at high latitudes cooled or remained unchanged.However, surface waters at high northern latitudes in the Atlantic Ocean aswell as in the eastern equatorial Atlantic cooled, while water temperatures remainedrelatively unchanged at most South Atlantic sites. Surface waters warmed in the southernmostAtlantic, off the tip of South Africa. By 8 Ma, the east-to-west asymmetry of thetemperature distribution in the tropical South Pacific Ocean had lessened. Surface watertemperatures had become quite similar to those of the Modern ocean except that those inthe equatorial Pacific Ocean were lower than today's. This is reflected in the latitudinalgradient of surface temperatures at 8 Ma which is less steep than that of moderntemperatures.The pattern of surface temperatures and their evolution through the Miocene isconsistent with the biogeographic distributions of planktonic foraminifera described byKennett et al. (this volume). The isotopic data provide a more detailed picture of theevolution of Miocene surface temperatures than had been hitherto available, and serveas a framework against which hypotheses can be tested regarding the cause of themiddle Miocene cooling of deep waters and the formation of the East Antarctic ice sheet.  PDF

URLhttps://doi.org/10.1130/mem163-p49
DOI10.1130/mem163-p49

Depth stratification of planktonic foraminifers in the Miocene ocean

TitleDepth stratification of planktonic foraminifers in the Miocene ocean
Publication TypeBook Chapter
Year of Publication1985
AuthorsKeller, G
Book TitleGeological Society of America Memoirs
Pagination177–196
PublisherGeological Society of America
Abstract

A depth stratification of planktonic foraminifers based on oxygen isotopic ranking is proposed for the Miocene. Species are grouped into surface, intermediate, and deep dwellers based upon oxygen isotopic composition of individual species. The depth stratification is applied to planktonic foraminiferal populations in three Miocene time-slices (21 Ma, 16 Ma, and 8 Ma) in the equatorial, north, west, and east Pacific. The late Miocene time-slice is compared with modern Pacific GEOSECS transect water-mass profiles of temperature and salinity in order to illustrate the similarities between the depth ranking of planktonic foraminifers and temperature and salinity conditions. The geographic distribution of inferred surface, intermediate, and deep water dwellers was found to be very similar to modern temperature profiles: surface dwellers appear to be associated with warmest temperatures (>20°C), upper intermediate water dwellers with temperatures between 10 and 20°C, and lower intermediate and deep water dwellers with temperatures below 10°C. Tropical high-salinity water appears to be associated with the upper intermediate Globorotalia menardii group in the modern ocean.

Depth stratification applied to two Miocene time-series analyses in the equatorial Pacific (Sites 77B and 289) indicates increased vertical and latitudinal provincialism between early, middle, and late Miocene time. The early and middle Miocene equatorial Pacific was dominated by the warm surface water group, which shows distinct east-west provincialism. This provincialism is interpreted as the periodic strengthening of the equatorial surface circulation during polar cooling phases. During the late Miocene the upper intermediate group increased and the surface group declines. At the same time the east-west provincialism disappeared. This faunal change may have been associated with the major Antarctic glaciation and resultant strengthening of the general gyral circulation and the strengthening of the Equatorial Countercurrent due to the closing of the Indonesian Seaway at that time.   PDF

URLhttps://doi.org/10.1130/mem163-p177
DOI10.1130/mem163-p177

Evolution of the Miocene ocean in the eastern North Pacific as inferred from oxygen and carbon isotopic ratios of foraminifera

TitleEvolution of the Miocene ocean in the eastern North Pacific as inferred from oxygen and carbon isotopic ratios of foraminifera
Publication TypeBook Chapter
Year of Publication1985
AuthorsBarrera, E, Keller, G, Savin, SM
Book TitleGeological Society of America Memoirs
Pagination83–102
PublisherGeological Society of America
Abstract

Oxygen and carbon isotopic ratios of planktonic and benthonic foraminifera have provided information about the evolution of the oceans at low- and mid-latitude sites in the Miocene eastern North Pacific Ocean.

DSDP Site 495 (12° N; 91° W) provides a record of early and middle Miocene oceanographic conditions in the eastern equatorial Pacific. Oxygen isotopic evidence indicates that G. sacculifer, D. altispira and G. siakensis were shallow-dwelling, tropical planktonic species. G. venezuelana deposited its test at greater depths, probably below the thermocline. Carbon isotopic evidence conflicts with that of the oxygen isotopes in that it suggests that G. siakensis calcified under conditions similar to those of G. venezuelana.

Temperature variability at Site 495 during early and middle Miocene time was relatively small. However, while middle Miocene deep waters at this site cooled, simultaneously with a major phase of growth of the Antarctic ice sheet, surface and near-surface waters warmed.

The oxygen isotopic record at Site 470 in the eastern North Pacific (29° N; 117° W) indicates that middle and late Miocene surface temperatures at this site were relatively stable, but were probably lower than modern surface temperatures.

At Site 173 (40° N; 125° W) middle and late Miocene surface temperatures were consistently lower than those at the more southerly Site 470, and were also significantly more variable. There is no indication that surface temperatures have changed significantly at Site 173 since late Miocene time. The inferred greater variability of surface temperatures at Site 173 may reflect greater variability of the intensity of upwelling at that site than at Site 470 during Miocene time.

At Site 495 both the planktonic and benthonic foraminiferal carbon isotopic records vary sympathetically with published benthonic foraminiferal isotopic records from the Atlantic and Pacific Oceans, indicating that the carbon isotopic ratios at that site largely reflect global fluctuations in the isotopic composition of dissolved inorganic carbon.

At Site 470 the planktonic carbon isotopic record fluctuates sympathetically with published benthonic records, indicating that the middle and late Miocene 13C/12C ratios of dissolved inorganic carbon in surface waters at this site reflected global fluctuations in 13C/12C. The planktonic carbon isotopic record at Site 173 could not be correlated with global carbon isotopic fluctuations, indicating that, in part, local effects controlled the 13C/12C ratio of dissolved inorganic carbon in surface waters at that site.   PDF

URLhttps://doi.org/10.1130/mem163-p83
DOI10.1130/mem163-p83

Miocene planktonic foraminiferal biogeography and paleoceanographic development of the Indo-Pacific region

TitleMiocene planktonic foraminiferal biogeography and paleoceanographic development of the Indo-Pacific region
Publication TypeBook Chapter
Year of Publication1985
AuthorsKennett, JP, Keller, G, Srinivasan, MS
Book TitleGeological Society of America Memoirs
Pagination197–236
PublisherGeological Society of America
Abstract

Biogeographic patterns of Pacific planktonic foraminifera have been quantitatively mapped for two time-slices in the early Miocene (22 and 16 Ma) and one in the late Miocene (8 Ma). Important differences are apparent between the early and late Miocene that resulted from changes in surface water circulation within the Pacific Ocean and between the tropical Pacific and Indian Oceans.

In the early Miocene, tropical Pacific planktonic foraminifera were dominated by different taxa in the eastern and western areas, but by the late Miocene the assemblages were similar across the entire tropical Pacific. East to west faunal differences were probably due to differences in the surficial water-mass structure and temperature. It is likely that a deeper thermocline existed in the west favoring shallow water dwellers such as Globigerinoides and Globigerina angustiumbilicata, and a shallower thermocline in the east favoring slightly deeper-dwelling forms, especially Globorotalia siakensis and G. mayeri. During the late Miocene a trans-equatorial assemblage developed, dominated by Globorotalia menardii-G. limbata and Globigerinoides groups. These faunal changes are interpreted to reflect both the development, during the middle Miocene, of the Equatorial Undercurrent system when the Indonesian Seaway effectively closed and the general strengthening of the gyral circulation and Equatorial Countercurrent that resulted from increased Antarctic glaciation and high-latitude cooling during the middle Miocene.

The trans-equatorial planktonic foraminiferal distribution patterns typical of the late Miocene did not persist to the present-day oceans when east-west differences are again evident. However, these differences in modern assemblages are exhibited within forms that usually inhabit deeper waters. There is a successive changing dominance from west to east of Pulleniatina obliquiloculata to Globorotalia tumida to Neoglobo-quadrina dutertrei. The modern west to east differences in these deeper-dwelling forms reflect an intensification of the Equatorial Undercurrent system and its shallowing towards the east to depths well within the photic zone. Shallow-water forms, such as Globigerinoides, maintain trans-tropical distribution patterns in the modern ocean unlike the early Miocene that lacked an effective equatorial countercurrent system in the Pacific.

The distribution of faunas in the North Pacific indicates that the gyral circulation system was only weakly developed in the early Miocene, but was strong by the late Miocene. In the northwest Pacific, temperate faunas were displaced northward as the Kuroshio Current intensified in the late Miocene. In the South Pacific, more distinct latitudinal faunal provinces appeared during the middle to late Miocene along with a northward expansion of the polar-subpolar provinces and contraction of the tropical province. These faunal changes resulted from the continued areal expansion of the polar and subpolar water masses as Australia drifted northward from Antarctica and from the steepening of pole to equator thermal gradients related to increased Antarctic glaciation.  PDF

URLhttps://doi.org/10.1130/mem163-p197
DOI10.1130/mem163-p197

Paleontologic data on the Age of the Orca Group, Alaska Report 85

TitlePaleontologic data on the Age of the Orca Group, Alaska Report 85
Publication TypeReport
Year of Publication1985
AuthorsPlafker, G, Keller, G, Barron, JD, ,
Series TitleUnited States Department of the Interior, Geological Survey
Document Number85-429
Abstract

The Orca Group is a widespread, very thick, and complexly deformed accretionary sequence of flysch and tholeiitic basalt in the Prince William Sound area of Alaska (Winkler, 1976; Winkler and Plafker, 1981). Despite a number of extensive field studies of the Orca Group, reliable data on the age of the unit has been exceedingly elusive. On the basis of sparse paleontologic and radiometric data, the sequence was assigned a Pal eocene and early Eocene(?) age (Addicott and Plafker, 1971; Plafker and Lanphere 1974; Winkler, 1976, Winkler and Plafker, 1981). New paleontologic data suggest that some strata assigned to the Orca Group are of middle Eocene age and possibly as young as late Eocene or Oligocene. However, data suggesting an age younger than about 50 Ma appear to be incompatible with radiometricanydetermined ages for plutons that intrude the Orca. This paper summarizes the published and unpublished paleontologic data from the Orca Group, considers their implications for the age of the unit, and points out the problems in age assignments. PDF

 

Middle Oligocene cooling from equatorial Pacific (DSDP) Site 77B

TitleMiddle Oligocene cooling from equatorial Pacific (DSDP) Site 77B
Publication TypeJournal Article
Year of Publication1984
AuthorsKeigwin, L, Keller, G
JournalGeology
Volume12
Pagination16
Abstract

An apparently complete 150-m Oligocene sequence of pelagic sediment at equatorial Pacific Deep Sea Drilling Project Site 77B has been analyzed for stable-isotope and quantitative planktonic foraminiferal studies. Lower abundance of inferred warm-water species and enrichment of 18O and 12C in foraminiferal tests during the interval 29 to 32 m.y. ago suggest cooler climate, lowered sea level, and significant volume of continental ice compared to earlier and later times in the Oligocene.  PDF

URLhttps://doi.org/10.1130/0091-7613(1984)12<16:mocfep>2.0.co;2
DOI10.1130/0091-7613(1984)12<16:mocfep>2.0.co;2

Paleoclimatic evidence for Cenozoic migration of Alaskan terranes

TitlePaleoclimatic evidence for Cenozoic migration of Alaskan terranes
Publication TypeJournal Article
Year of Publication1984
AuthorsKeller, G, von Huene, R, McDougall, K, Bruns, TR
JournalTectonics
Volume3
Pagination473–495
Date Publishedaug
Abstract

Chronostratigraphic and paleoclimatic comparisons of microfossils from deep-sea cores, from samples of an exploratory drill hole, and from dredged rock of the Gulf of Alaska with coeval microfossil assemblages on the North American continent provide constraints on the northward migration of the Yakutat block, the Prince William terrane and the Pacific plate during Tertiary time. The comparative paleolatitudes of microfauna and flora provide three main constraints. (1) The Prince William terrane was in its present position with respect to North America (at high latitudes, 50° ± 5°N) by middle Eocene time (40–42 Ma), consistent with models derived from paleomagnetic data. (2) The adjacent Yakutat block was 30° ± 5° south of its present position in early Eocene (50 Ma), 20° ± 5° south in middle Eocene (40–44 Ma), and 15° ± 5° south in late Eocene time (37–40 Ma), thus requiring a northward motion of about 30° since 50 Ma. Moreover, the Yakutat block was at least 10° south of the Prince William terrane during Eocene time. These data are consistent with migration of the Yakutat block with the Pacific and Kula plates for at least the last 50 Ma. (3) site 192 on the Pacific plate was at about 15° ± 5°N latitude in the late Cretaceous (68 Ma), at 30° ± 5°N in early Eocene (50 Ma), at 40° ± 5°N in middle Eocene (40–44 Ma), at 45° ± 5°N in late Eocene (37–40 Ma), and north of 50° ± 5°N in latest Eocene to early Oligocene time (34–37 Ma). These paleolatitudes, based on planktonic foraminiferal assemblages, indicate northward drift consistent with the North America-Pacific plate reconstructions from about 68 Ma to 40 Ma (Engebretson, 1982). However, from Cretaceous to early Eocené time, faunal data indicate significantly lower latitudinal positions, and from Oligocwne to early Miocene time, significantly higher latitudinal positions. These discrepancies can be explained by the northward expansion of tropical faunas during the globally warm early Tertiary and southward expansion of cold subarctic faunas as a result of global cooling during Oligocene time.   PDF

URLhttps://doi.org/10.1029/tc003i004p00473
DOI10.1029/tc003i004p00473

Paleoceanographic implications of Miocene deep-sea hiatuses

TitlePaleoceanographic implications of Miocene deep-sea hiatuses
Publication TypeJournal Article
Year of Publication1983
AuthorsKeller, G, Barron, JA
JournalGeological Society of America Bulletin
Volume94
Pagination590
Abstract

Miocene paleoceanographic evolution exhibits major changes resulting from the opening and closing of passages, the subsequent changes in oceanic circulation, and development of major Antarctic glaciation. The consequences and timing of these events can be observed in variations in the distribution of deep-sea hiatuses, sedimentation patterns, and biogeographic distribution of planktic organisms.

The opening of the Drake Passage in the latest Oligocene to early Miocene (25-20 Ma) resulted in the establishment of the deep circumpolar current, which led to thermal isolation of Antarctica and increased global cooling. This development was associated with a major turnover in planktic organisms, resulting in the evolution of Neogene assemblages and the eventual extinction of Paleogene assemblages. The erosive patterns of two widespread hiatuses (PH, 23.0-22.5 Ma; and NH 1, 20-18 Ma) indicate that a deep circumequatorial circulation existed at this time, characterized by a broad band of carbonate-ooze deposition. Siliceous sedimentation was restricted to the North Atlantic and a narrow band around Antarctica.

A major reorganization in deep-sea sedimentation and hiatus distribution patterns occurred near the early/middle Miocene boundary, apparently resulting from changes in oceanic circulation. Beginning at this time, deep-sea erosion occurred throughout the Caribbean (hiatus NH 2, 16-15 Ma), suggesting disruption of the deep circumequatorial circulation and northward deflection of deep currents, and/o r intensification of the Gulf Stream. Sediment distribution patterns changed dramatically with the sudden appearance of siliceous-ooze deposition in the marginal and east equatorial North Pacific by 16.0 to 15.5 Ma, coincident with the decline of siliceous sedimentation in the North Atlantic. This silica switch may have been caused by the introduction of Norwegian Overflow Water into the North Atlantic acting as a barrier to outcropping of silica-rich Antarctic Bottom Water. The main aspects of the present oceanic circulation system and sediment distribution pattern were established by 13.5 to 12.5 Ma (hiatus NH 3), coincident with the establishment of a major East Antarctic ice cap. Antarctic glaciation resulted in a broadening belt of siliceous-ooze deposition around Antarctica, increased siliceous sedimentation in the marginal and east equatorial North Pacific and Indian Oceans, and further northward restriction of siliceous sediments in the North Atlantic. Periodic cool climatic events were accompanied by lower eustatic sea levels and widespread deep-sea erosion at 12 to 1 1 Ma (NH 4), 10 to 9 Ma (NH 5), 7.5 to 6.2 Ma (NH 6), and 5.2 to 4.7 Ma (NH 7).  PDF

URLhttps://doi.org/10.1130/0016-7606(1983)94<590:piomdh>2.0.co;2
DOI10.1130/0016-7606(1983)94<590:piomdh>2.0.co;2

Paleotemperature Oscillations in the Middle and Late Miocene of the Northeastern Pacific

TitlePaleotemperature Oscillations in the Middle and Late Miocene of the Northeastern Pacific
Publication TypeJournal Article
Year of Publication1983
AuthorsBarron, JA, Keller, G
JournalMicropaleontology
Volume29
Pagination150
Abstract

The paleoclimatic and paleoceanographic history of the Middle and Late Miocene marginal eastern North Pacific has been studied in a north-to-south transect encompassing DSDP Site 173, the Newport Beach surface section, and DSDP Site 470, based on quantitative diatom and planktic foraminiferal analyses. Fourteen cold and 12 warm events that show close agreement with other microfossil studies as well as oxygen isotope records from low-latitude Pacific sites have been identified. Hiatuses are recognized at 7 to 6.5 Ma, 9.8 to 8.5 Ma, and 12 to 11 Ma at the three reference localities, and they correspond to widely recognized deep-sea hiatuses in the World Ocean.   PDF

URLhttps://doi.org/10.2307/1485565
DOI10.2307/1485565

Biochronology and paleoclimatic implications of Middle Eocene to Oligocene planktic foraminiferal faunas

TitleBiochronology and paleoclimatic implications of Middle Eocene to Oligocene planktic foraminiferal faunas
Publication TypeJournal Article
Year of Publication1983
AuthorsKeller, G
JournalMarine Micropaleontology
Volume7
Pagination463–486
Date Publishedapr
Abstract

Planktic foraminiferal assemblages have been analyzed quantitatively in six DSDP sites in the Atlantic (Site 363), Pacific (Sites 292, 77B, 277), and Indian Ocean (Sites 219, 253) in order to determine the nature of the faunal turnover during Middle Eocene to Oligocene time. Biostratigraphic ranges of taxa and abundance distributions of dominant species are presented and illustrate striking similarities in faunal assemblages of low latitude regions in the Atlantic, Pacific and Indian oceans. A high resolution biochronology, based on dominant faunal characteristics and 55 datum events, permits correlation between all three oceans with a high degree of precision. Population studies provide a view of the global impact of the paleoclimatic and paleoceanographic changes occurring during Middle Eocene to Oligocene time.

Planktic foraminiferal assemblage changes indicate a general cooling trend between Middle Eocene to Oligocene time, consistent with previously published oxygen isotope data. Major faunal changes, indicating cooling episodes, occur, however, at discrete intervals: in the Middle Eocene 44-43 Ma (P13), the Middle/Late Eocene boundary 41-40 Ma (P14P15), the Late Eocene 39-38 Ma (P15P16), the Eocene/Oligocene boundary 37-36 Ma (P18), and the Late Oligocene 31-29 Ma (P20P21). With the exception of the E0 boundary, faunal changes occur abruptly during short stratigraphic intervals, and are characterized by major species extinctions and first appearances. The Eocene/Oligocene boundary cooling is marked primarily by increasing abundances of cool water species. This suggests that the E0boundary cooling, which marks a major event in the oxygen isotope record affected planktic faunas less than during other cooling episodes. Planktic foraminiferal faunas indicate that the E0 boundary event is part of a continued cooling trend which began during the Middle Eocene.

Two hiatus intervals are recognized in low and high latitude sections at the Middle/Late Eocene boundary and in the Late Eocene (P15P16). These hiatuses suggest that vigorous bottom water circulation began developing in the Middle Eocene, consistent with the onset of the faunal cooling trend, and well before the development of the psychrosphere at the E0boundary.   PDF

URLhttps://doi.org/10.1016/0377-8398(83)90011-7
DOI10.1016/0377-8398(83)90011-7

Paleoclimatic analyses of middle Eocene through Oligocene planktic foraminiferal faunas

TitlePaleoclimatic analyses of middle Eocene through Oligocene planktic foraminiferal faunas
Publication TypeJournal Article
Year of Publication1983
AuthorsKeller, G
JournalPalaeogeography, Palaeoclimatology, Palaeoecology
Volume43
Pagination73–94
Date Published08/1983
Abstract

Quantitative faunal analyses and oxygen isotope ranking of individual planktic foraminiferal species from deep sea sequences of three oceans are used to make paleoceanographic and paleoclimatic inferences. Species grouped into surface, intermediate and deep water categories based on δ18O values provide evidence of major changes in water-mass stratification, and individual species abundances indicate low frequency cool-warm oscillations. These data suggest that relatively stable climatic phases with minor cool-warm oscillations of ∼0.5 m.y. frequency are separated by rapid cooling events during middle Eocene to early Oligocene time.

Five major climatic phases are evident in the water-mass stratification between middle Eocene through Oligocene time. Phase changes occur at P14/P15, P15/P16, P20/P21 and P21/P22 Zone boundaries and are marked by major faunal turnovers, rapid cooling in the isotope record, hiatuses and changes in the eustatic sea level. A general cooling trend between middle Eocene to early late Oligocene is indicated by the successive replacement of warm middle Eocene surface water species by cooler late Eocene intermediate water species and still cooler Oligocene intermediate and deep water species. Increased water-mass stratification in the latest Eocene (P17), indicated by the coexistence of surface, intermediate and deep dwelling species groups, suggest that increased thermal gradients developed between the equator and poles nearly coincident with the development of the psychrosphere. This pattern may be related to significant ice accumulation between late Eocene and early late Oligocene time.  PDF

URLhttps://doi.org/10.1016/0031-0182(83)90049-4
DOI10.1016/0031-0182(83)90049-4

Multiple microtektite horizons in upper eocene marine sediments: no evidence for mass extinctions.

TitleMultiple microtektite horizons in upper eocene marine sediments: no evidence for mass extinctions.
Publication TypeJournal Article
Year of Publication1983
AuthorsKeller, G, D'Hondt, S, Vallier, TL
JournalScience
Volume221
Issue4606
Abstract

Microtektites have been recovered from three horizons in eight middle Eocene to middle Oligocene marine sediment sequences. Five of these occurrences are coeval and of latest Eocene age (37.5 to 38.0 million years ago); three are coeval and of early late Eocene age (38.5 to 39.5 million years ago); and three are of middle Oligocene age (31 to 32 million years ago). In addition, rare probable microtektites have been found in sediments with ages of about 36.0 to 36.5 million years. The microtektite horizon at 37.5 to 38.0 million years can be correlated with the North American tektite-strewn field, which has a fission track age (minimum) of 34 to 35 million years and a paleomagnetic age of 37.5 to 38.0 million years. There is no evidence for mass faunal extinctions at any of the microtektite horizons. Many of the distinct faunal changes that occurred in the middle Eocene to middle Oligocene can be related to the formation of the Antarctic ice sheet and the associated cooling phenomena and intensification of bottom currents that led to large-scale dissolution of calcium carbonate and erosion, which created areally extensive hiatuses in the deep-sea sediment records. The occurrence of microtektite horizons of several ages and the lack of evidence for faunal extinctions suggest that the effects of extraterrestrial bolide impacts may be unimportant in the biologic realm during middle Eocene to middle Oligocene time.

North Pacific Late Miocene correlations using microfossils, stable isotopes, percent (CaCO)3, and magnetostratigraphy

TitleNorth Pacific Late Miocene correlations using microfossils, stable isotopes, percent (CaCO)3, and magnetostratigraphy
Publication TypeJournal Article
Year of Publication1982
AuthorsKeller, G, Barron, JA, Burckle, LH
JournalMarine Micropaleontology
Volume7
Pagination327–357
Date Publishedsep
URLhttps://doi.org/10.1016/0377-8398(82)90009-3
DOI10.1016/0377-8398(82)90009-3

Planktonic foraminiferal biostratigraphy, paleoceanographic implications, and deep sea correlation of the Plio-Pleistocene Centerville Beach section, Northern California

TitlePlanktonic foraminiferal biostratigraphy, paleoceanographic implications, and deep sea correlation of the Plio-Pleistocene Centerville Beach section, Northern California
Publication TypeJournal Article
Year of Publication1981
AuthorsKeller, G, Ingle, Jr., JC
JournalGeological Society of America Special Paper
Volume181
Pagination127-135

Integrated planktic foraminiferal and diatum biochronology for the northeast Pacific and the Monterey Formation, in The Monterey Formation and related siliceous rocks of California

TitleIntegrated planktic foraminiferal and diatum biochronology for the northeast Pacific and the Monterey Formation, in The Monterey Formation and related siliceous rocks of California
Publication TypeJournal Article
Year of Publication1981
AuthorsKeller, G, Barron, JA
JournalPacific Section, Society of Economic Paleontologists and Mineralogists
Pagination43-54

Benthic foraminiferal biofacies of the eastern Pacific margin between 40°S and 32°N, in Quaternary depositional environments of the Pacific coast

TitleBenthic foraminiferal biofacies of the eastern Pacific margin between 40°S and 32°N, in Quaternary depositional environments of the Pacific coast
Publication TypeConference Paper
Year of Publication1980
AuthorsIngle, Jr., JC, Keller, G
Conference NamePacific Coast Paleogeography Symposium 4
PublisherSociety of Economic Paleontologists and Mineralogists
Conference LocationLos Angeles, CA
Other Numbersp. 341-355

Middle to late Miocene planktonic foraminiferal datum levels and paleoceanography of the North and Southeastern Pacific Ocean

TitleMiddle to late Miocene planktonic foraminiferal datum levels and paleoceanography of the North and Southeastern Pacific Ocean
Publication TypeJournal Article
Year of Publication1980
AuthorsKeller, G
JournalMarine Micropaleontology
Volume5
Pagination249–281
Date Publishedjan
URLhttps://doi.org/10.1016/0377-8398(80)90013-4
DOI10.1016/0377-8398(80)90013-4

Benthic Foraminifers and Paleobathymetry of the Japan Trench Area, Leg 57, Deep Sea Drilling Project

TitleBenthic Foraminifers and Paleobathymetry of the Japan Trench Area, Leg 57, Deep Sea Drilling Project
Publication TypeBook Chapter
Year of Publication1980
AuthorsKeller, G
Book TitleInitial Reports of the Deep Sea Drilling Project
PublisherU.S. Government Printing Office
URLhttps://doi.org/10.2973/dsdp.proc.5657.124.1980
DOI10.2973/dsdp.proc.5657.124.1980

Benthic Foraminiferal Biofacies, Sediments and Water Masses of the Southern Peru-Chile Trench Area, Southeastern Pacific Ocean

TitleBenthic Foraminiferal Biofacies, Sediments and Water Masses of the Southern Peru-Chile Trench Area, Southeastern Pacific Ocean
Publication TypeJournal Article
Year of Publication1980
AuthorsIngle, JC, Keller, G, Kolpack, RL
JournalMicropaleontology
Volume26
Pagination113
URLhttps://doi.org/10.2307/1485435
DOI10.2307/1485435

Site 441: Japan Trench Lower Slope, Leg 57

TitleSite 441: Japan Trench Lower Slope, Leg 57
Publication TypeReport
Year of Publication1980
Authorsvon Huene, R, Keller, G, Arthur, MA, Barron, JA, Bell, GD, Cadet, J-P, Carson, B, Fujioka, K, Honza, E, Nasu, N, Moore, GW, Reynolds, R, Sato, S, Shaffer, BL
Series TitleInitial Reports, Deep Sea Drilling Project
Document Numberv. 56 and 57
Pagination319-354
URLhttp://deepseadrilling.org/56_57/volume/dsdp56_57pt1_05.pdf
Contents13 figures, 2 tables

Late neogene planktonic foraminiferal biostratigraphy and paleoceanography of the northwest Pacific (DSDP) site 296

TitleLate neogene planktonic foraminiferal biostratigraphy and paleoceanography of the northwest Pacific (DSDP) site 296
Publication TypeJournal Article
Year of Publication1979
AuthorsKeller, G
JournalPalaeogeography, Palaeoclimatology, Palaeoecology
Volume27
Pagination129–154
Date Publishedjan
URLhttps://doi.org/10.1016/0031-0182(79)90097-x
DOI10.1016/0031-0182(79)90097-x

Early Pliocene to Pleistocene planktonic foraminiferal datum levels in the North Pacific: (DSDP) Sites 173, 310, 296

TitleEarly Pliocene to Pleistocene planktonic foraminiferal datum levels in the North Pacific: (DSDP) Sites 173, 310, 296
Publication TypeJournal Article
Year of Publication1979
AuthorsKeller, G
JournalMarine Micropaleontology
Volume4
Pagination281–294
Date Publishedjan
URLhttps://doi.org/10.1016/0377-8398(79)90021-5
DOI10.1016/0377-8398(79)90021-5

Morphologic variation of Neogloboquadrina pachyderma (Ehrenberg) in sediments of the marginal and central Northeast Pacific Ocean and paleoclimatic interpretation

TitleMorphologic variation of Neogloboquadrina pachyderma (Ehrenberg) in sediments of the marginal and central Northeast Pacific Ocean and paleoclimatic interpretation
Publication TypeJournal Article
Year of Publication1978
AuthorsKeller, G
JournalThe Journal of Foraminiferal Research
Volume8
Pagination208–224
Date Publishedjul
URLhttps://doi.org/10.2113/gsjfr.8.3.208
DOI10.2113/gsjfr.8.3.208

Late Neogene planktonic foraminiferal biostratigraphy and paleoceanography of the northeastern Pacific: evidence from (DSDP) Sites 173 and 310 at the North Pacific Front

TitleLate Neogene planktonic foraminiferal biostratigraphy and paleoceanography of the northeastern Pacific: evidence from (DSDP) Sites 173 and 310 at the North Pacific Front
Publication TypeJournal Article
Year of Publication1978
AuthorsKeller, G
JournalThe Journal of Foraminiferal Research
Volume8
Pagination332–349
Date Publishedoct
URLhttps://doi.org/10.2113/gsjfr.8.4.332
DOI10.2113/gsjfr.8.4.332

Late neogene biostratigraphy and paleoceanography of (DSDP) site 310 Central North Pacific and correlation with the Southwest Pacific

TitleLate neogene biostratigraphy and paleoceanography of (DSDP) site 310 Central North Pacific and correlation with the Southwest Pacific
Publication TypeJournal Article
Year of Publication1978
AuthorsKeller, G
JournalMarine Micropaleontology
Volume3
Pagination97–119
Date Publishedjun
URLhttps://doi.org/10.1016/0377-8398(78)90001-4
DOI10.1016/0377-8398(78)90001-4

Late Neogene paleoceanography and planktonic foraminiferal datum levels of mid latitudes of the North Pacific

TitleLate Neogene paleoceanography and planktonic foraminiferal datum levels of mid latitudes of the North Pacific
Publication TypeConference Proceedings
Year of Conference1978
AuthorsKeller, G
Conference Namein Correlation of tropical through high latitude marine Neogene deposits of the Pacific Basin
Date Publishedp. 28-29
PublisherInternational Correlation Programme, Project 114
Conference LocationStanford, CA