GERTA KELLER PUBLICATIONS

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

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

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

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

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, Stueben, D, Berner, Z, Ramanivosoa, B, Randriamanantenasoa, A
JournalMarine Micropaleontology
Volume47
Pagination17–70
Date Publishedjan
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

URLhttps://doi.org/10.1016/s0377-8398(02)00094-4
DOI10.1016/s0377-8398(02)00094-4

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

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

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

Pages