Gerta Keller

Gerta Keller
Princeton University | PU · Department of Geosciences

PhD

About

352
Publications
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Publications

Publications (352)
Article
Full-text available
The late Maastrichtian witnessed substantial surges in Deccan volcanism, prompting the hypothesis that these voluminous pulses may have instigated repeated episodes of ocean acidification during this period. The Cretaceous-Palaeogene (K/Pg) boundary at Bidart (France) is preceded by a ∼0.5 m thick interval with geochemical and taphonomic vestiges o...
Conference Paper
Full-text available
The final 0.5 m of the Cretaceous-Paleogene (K/Pg) boundary at Bidart (France) is characterized by geochemical, taphonomic, and biotic vestiges of an ocean acidification event linked with Deccan volcanism. The larger (>150 μm) planktic foraminifera morphogroups show varying populations (absolute abundance), with lowered abundances within the Deccan...
Conference Paper
Full-text available
The final 0.5-meter interval preceding the Cretaceous-Paleogene (K/Pg) boundary at Bidart (France) is critical as it records anomalously low bulk rock magnetic susceptibility and high mercury content indicating acidification linked with ongoing Deccan volcanism. Planktic foraminifera test taphonomy supports this possibility through poor preservatio...
Preprint
Full-text available
The Paleocene-Eocene Thermal Maximum (PETM) was identified for the first time in two sections (Bongue and Dibamba) from the Douala sub-basin located in the Gulf of Guinea, Cameroon. This discovery was based on a multidisciplinary approach including benthic and planktic foraminifera, ostracods, major and trace elements, mercury, carbon stable isotop...
Chapter
During the last decades, Egypt became a focal point for studying the climate and paleoenvironmental changes during the late Paleocene early of Eocene that is known as the Paleocene-Eocene Thermal Maximum (PETM). This chapter sheds light on the climatic and paleoenvironmental changes recorded from the Egyptian sedimentary record, based on: biostrati...
Preprint
Full-text available
Large Igneous Provinces (LIPs) have been widely studied over the past decades due to their likely link to mass extinction events. Previous work involving U-Pb zircon dating of the Deccan lava flows indicates that the main phase-2 began 250 Ka before the Cretaceous-Paleogene (K-Pg) mass extinction boundary and continued into the early Danian, sugges...
Conference Paper
Full-text available
The Late Maastrichtian Deccan volcanic pulses contributed to a cumulative biotic stress that set the stage for the Cretaceous-Palaeogene boundary (KPB) mass extinction. The high-flux emissions of volcanogenic CO2 and SO2 into the atmosphere likely led to ocean acidification. The resultant carbonate crisis has been hypothesized as a key stressor for...
Article
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We report the Narmada Seaway began in India during the largest global sea-level transgression and Oceanic Anoxic Event 2 (OAE2) δ¹³C excursion during the late Cenomanian to early Turonian. The transgression progressed eastward during the Turonian-Coniacian and reached Jhilmili by the end of the Maastrichtian. During this time the Narmada and Godava...
Article
Early Eocene rift basins sediments in western and northwestern India contain deposits including lignite. These rift basins were formed during the early stage of the India - Eurasia collision. The Sedimentary successions in the studied five lignite mines are stratigraphically similar. In these successions, there are two thick lignite units, called t...
Article
Mercury (Hg) anomalies linked to Large Igneous Provinces (LIP) volcanism have been identified in sediments across all five major mass extinctions in Earth's history. This study tests whether Hg in marine sediments is a reliable proxy linking Deccan Traps volcanic eruptions to late Maastrichtian global climate warming and the mass extinction at the...
Chapter
This volume covers new developments and research on mass extinctions, volcanism, and impacts, ranging from the ancient Central Iapetus magmatic province linked with the Gaskiers glaciation to thermogenic degassing in large igneous provinces, the global mercury enrichment in Valanginian sediments, and the Guerrero-Morelos carbonate platform response...
Article
The end-Cretaceous mass extinction (66 Ma) has long been associated with the Chicxulub impact on the Yucatan Peninsula. However, consensus on the age of this impact has remained controversial because of differing interpretations on the stratigraphic position of Chicxulub impact spherules relative to the mass extinction horizon. One side argues that...
Article
Full-text available
Two timelines for extinction The Cretaceous-Paleogene extinction that wiped out the nonavian dinosaurs 66 million years ago was correlated with two extreme events: The Chicxulub impact occurred at roughly the same time that massive amounts of lava were erupting from the Deccan Traps (see the Perspective by Burgess). Sprain et al. used argon-argon d...
Conference Paper
The Paleocene-Eocene Thermal Maximum (PETM, ~55.5 Myr) was a period of rapid warming resulting from major changes in the carbon cycle and has been cited as the closest historical analogue to anthropogenic carbon release. Up to now, modeling studies of the PETM used either a low-resolution coupled model of the ocean and atmosphere with prescribed CO...
Article
Full-text available
The Cretaceous-Paleogene boundary (KPB) mass extinction (~ 66.02 Ma) and the Paleocene-Eocene Thermal Maximum (PETM) (~ 55.8 Ma) are two remarkable climatic and faunal events in Earth's history that have implications for the current Anthropocene global warming and rapid diversity loss. Here we evaluate these two events at the stratotype localities...
Article
Full-text available
The contribution of the Deccan Traps (west-central India) volcanism in the Cretaceous-Paleogene (KPg) crisis is still a matter of debate. Recent U-Pb dating of zircons interbedded within the Deccan lava flows indicate that the main eruptive phase (>1.1 × 106 km3 of basalts) initiated ∼250 k.y. before and ended ∼500 k.y. after the KPg boundary. Howe...
Article
Full-text available
Late Maastrichtian through middle Eocene planktic foraminiferal biostratigraphy and erosion patterns from three Cauvery basin wells are compared with the Krishna-Godavari basin, Madagascar and South Atlantic Site 525A. Maastrichtian sedimentation appears continuous at DSDP site 525A and substantially complete in the Cauvery basin and Madagascar for...
Article
Full-text available
Deep-sea sections in the North Atlantic are claimed to contain the most complete sedimentary records and ultimate proof that the Chicxulub impact is Cretaceous-Tertiary boundary (KTB) in age and caused the mass extinction. A multi-disciplinary study of North Atlantic DSDP Sites 384, 386 and 398, based on high-resolution planktonic foraminiferal bio...
Article
Full-text available
The late Maastrichtian was a time of major climate, evolution and extinction extremes. Rapid climate warming of 2–3 °C in intermediate waters between 69.5 and 68 Ma (top C31r to base C30n) accompanied maximum evolutionary diversification (43% increase, zone CF5 to low CF4) in planktic foraminiferal history, followed immediately by a cluster of exti...
Conference Paper
Preliminary results show poor planktic foraminifer test preservation in the top ~1 m (zone CF1) at Agost, correlative with high-stress conditions preceding the mass extinction horizon at Bidart, Gamsbach and Elles (Tunisia). Correlative zone CF1 sediments in the eastern Tethys (Egypt, Israel) show inverse correlation between carbonate preservation...
Article
The discovery of a new Cretaceous/Palaeogene (K/Pg) bathyal marine sequence on Gorgonilla Island, SW Colombia, extends the presence of Chicxulub impact spherule deposits to the Pacific region of northern South America and to the Eastern Pacific Ocean. The Gorgonilla spherule layer is approximately 20 mm thick and consists of extraordinarily well-pr...
Conference Paper
Full-text available
The discovery of a new Cretaceous/Paleogene (K/Pg) bathyal marine sequence on Gorgonilla Island, SW Colombia, extends the presence of Chicxulub spherule deposits to northern South America and to the Eastern Pacific Ocean. At the time of the Chicxulub impact, Gorgonilla was located approximately 2700-3000 km SW of the impact site. The Gorgonilla sph...
Conference Paper
The Maastrichtian (C31-C30n) was a time of major environmental changes that record evolutionary diversification in planktic foraminifera as well as a minor extinction associated with climate change and high carbonate dissolution. Although these changes have been observed worldwide, their cause(s) remain speculative. Here we report on these events b...
Conference Paper
The cause for the end-Cretaceous mass extinction (KTB) has long been attributed solely to the Chicxulub impact based on two major assumptions: (1) the Chicxulub impact trumped any earth-derived potential cause, and (2) Deccan volcanism played no significant role. Both of these assumptions have been challenged in recent years based on evidence that:...
Conference Paper
Highly diversified planktic foraminiferal assemblages (~65 species) prevailed in the early late Maastrichtian (mid C31n, ~68.8 Ma) at the South Atlantic DSDP Site 525A. A rapid warming (~2°C deep water) at the base CF4/ top C31n is associated with carbonate dissolution and enhanced planktic test-fragmentation indicative of ocean acidification. A su...
Article
Full-text available
Mass extinctions generally involve a complex array of interrelated causes and are best evaluated by a multi-proxy approach as applied here for the end-Cretaceous mass extinction. This study documents and compares the planktic foraminiferal records, carbonate dissolution effects, stable isotopes, and magnetic susceptibility in France (Bidart), Austr...
Article
Full-text available
Recent studies indicate that the bulk (80%) of Deccan trap eruptions occurred over a relatively short time interval in magnetic polarity C29r, whereas multi-proxy studies from central and southeastern India place the Cretaceous-Paleogene (K/Pg) mass extinction near the end of this main phase of Deccan volcanism suggesting a cause-and-effect relatio...
Chapter
Full-text available
Environmental changes linked to Deccan volcanism are still poorly known. A major limitation resides in the paucity of direct Deccan volcanism markers and in the geologically short interval where both impact and volcanism occurred, making it hard to evaluate their contributions to the mass extinction. We investigated the low-magnetic-susceptibility...
Chapter
Full-text available
Deccan volcanism, one of Earth’s largest fl ood basalt provinces, erupted ~80% of its total volume (phase 2) during a relatively short time in the uppermost Maastrichtian paleomagnetic chron C29r and ended with the Cretaceous-Tertiary boundary mass extinction. Full biotic recovery in the marine realm was delayed at least 500 k.y. or until after the...
Article
Full-text available
We investigated the Paleocene-Eocene boundary GSSP (Dababiya quarry) near Luxor, Egypt, in two nearby (25m and 50m) sequences based on highresolution biostratigraphy, lithostratigrapy, mineralogy and geochemistry. Results confirm the many positive aspects of the Dababiya GSSP but also show potentially serious limiting factors: (1) the GSSP is locat...
Article
Full-text available
The late Paleocene - Early Eocene boundary (56Ma) is marked by the warmest climate period of the Cenozoic, known as the Paleocene-Eocene Thermal Maximum (PETM). Most notably, the culprit behind it was a massive injection of heattrapping greenhouse gases into the atmosphere and oceans, comparable in volume to what our persistent burning of fossil fu...
Article
Full-text available
The Paleocene-Eocene thermal maximum (PETM) shows an extraordinary drop in both δ13Ccarb and δ13Corg values, suggesting that a massive amount of 12C-rich carbon dioxide was released into the atmosphere in a very short time (on the order of few hundred ky). The Dababiya GSSP (Luxor, Egypt) is thought to be the most complete known PETM section. The e...
Article
Full-text available
The Naredi Formation of Kutch, Gujarat, India, is early Eocene in age and marks the first marine transgression above the last Deccan traps. Sediment deposition occurred in a shallow inner shelf environment that varied from a brackish lagoon to brackish, normal inner shelf and to marginal marine environments. The section can be divided into 2 main t...
Article
Full-text available
The Naredi Formation in southwestern Kutch overlies the last Deccan Trap deposited during the early Paleocene. The lower part of the Naredi Formation (2.8-4.2 m from base) is of early Eocene (Ypresian) age (SBZ8, E4) based on larger foraminifera and rare planktic foraminifera, whereas the upper part (9.3-11 m, including the Assilina limestone) is o...
Article
Deccan volcanism occurred in three intense phases of relatively short duration: phase 1 spanning the paleomagnetic chron C30r/C30n boundary (planktic foraminiferal CF4), phase 2 in the latest Maastrichtian C29r (zones CF1–CF2), and phase 3 in the early Danian C29n (P1b). This study explores the nature of paleoenvironmental changes correlative with...
Article
Full-text available
Hurricanes play an important role in shaping the coast of Louisiana. Although the sedimentary signatures of hurricane deposits have been documented in several different coastal environments along the northern Gulf coast, no studies have as yet documented the signatures in wetlands adjacent to large, inland brackish water bodies. In this paper we pr...
Article
The Palaeocene–Eocene Thermal Maximum (PETM) interval at the Wadi Nukhul section (Sinai, Egypt) is represented by a 10 cm thick condensed clay-rich layer corresponding to the NP9a–NP9b nannofossil subzone boundary. The Wadi Nukhul Palaeocene–Eocene boundary (PEB) is characterized by (1) an abrupt negative excursion in carbonate and organic carbon i...
Article
The Natural History Museum in London recently hosted an international, multidisciplinary conference that brought together 150 researchers in geology, geophysics, geochemistry, volcanology, sedimentology, paleontology, and astronomy to review and assess recent research into the causes of mass extinction events. Participants included experts as well...
Data
ABSTRACT The Palaeocene–Eocene boundary (PEB), 55.8 Ma ago (Wester-hold et al. 2009), is a critical time interval in environmental changes and subsequent biotic changes. The global warming that started in the late Palaeocene and continued during the early Eocene known as the Palaeocene–Eocene Thermal Maximum (PETM), where the PEB transition interva...
Article
Full-text available
Abstract – The Chicxulub impact is commonly believed to have caused the Cretaceous–Tertiary boundary mass extinction and a thin impact spherule layer in the North Atlantic and Caribbean is frequently cited as proof. We evaluated this claim in the seven best North Atlantic and Caribbean Cretaceous–Tertiary boundary sequences based on high-resolution...
Data
Full-text available
The Palaeocene–Eocene boundary (PEB), 55.8 Ma ago (Wester-hold et al. 2009), is a critical time interval in environmental changes and subsequent biotic changes. The global warming that started in the late Palaeocene and continued during the early Eocene known as the Palaeocene–Eocene Thermal Maximum (PETM), where the PEB transition interval shows e...
Article
Full-text available
The Cretaceous-Tertiary boundary (KTB) transition of the Poty Quarry near Recife, NE Brazil, is the most distant locality (7800 km from Yucatan) with reported Chicxulub impact-tsunami deposits, impact spherules and Ir anomaly. Investigations based on sedimentology, biostratigraphy, mineralogy, stable isotopes and elemental geochemistry failed to co...
Article
Full-text available
The Palaeocene–Eocene Thermal Maximum (PETM) interval at the Wadi Nukhul section (Sinai, Egypt) is represented by a 10 cm thick condensed clay-rich layer corresponding to the NP9a–NP9b nannofossil subzone boundary. The Wadi Nukhul Palaeocene–Eocene boundary (PEB) is characterized by (1) an abrupt negative excursion in carbonate and organic carbon i...
Article
In C29r below the Cretaceous-Tertiary boundary (KTB) massive Deccan Trap eruptions in India covered an area the size of France or Texas and produced the world’s largest and longest lava megaflows 1500 km across India through the Krishna–Godavari (K–G) Basin into the Bay of Bengal. Investigation of ten deep wells from the K–G Basin revealed four lav...
Article
The stratigraphy, faunal changes, and geochemistry of deep-sea sediments associated with late Eocene microtektite and microspherule layers are reported. Microprobe analyses of major element compositions of microspherules show that, although there is some compositional overlap in all three late Eocene layers as well as with the Pleistocene Australas...
Article
The Paleocene Eocene Thermal Maximum (PETM, 55.5Ma) is globally related with the extinction of deep benthic foraminifera, the diversification of both plancktic foraminifera and mammals. In India, the tempo and timing of mammals dispersion, their association with the PETM or EECO (Early Eocene Climatic Optimum) and the India- Asia collision remain u...