Ellen ThomasYale University | YU · Department of Geology and Geophysics
Ellen Thomas
PhD, University of Utrecht, Netherlands
About
360
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Introduction
Research focused on benthic foraminifera, from coastal salt marshes to the deep sea, from living to late Ctetaceous.
Additional affiliations
January 2013 - present
January 2000 - present
Wesleyan University
Description
- Research professor
October 1992 - present
Publications
Publications (360)
Understanding the sensitivity of species-level responses to long-term warming will become increasingly important as we look towards a warmer future. Here, we examine photosymbiont associations in planktic foraminifera at Shatsky Rise (ODP Site 1209, Pacific Ocean) across periods of global warming of differing magnitude and duration. We compare publ...
This volume pays tribute to the great career and extensive and varied scientific accomplishments of Walter Alvarez, on the occasion of his 80th birthday in 2020, with a series of papers related to the many topics he covered in the past 60 years: Tectonics of microplates, structural geology, paleomagnetics, Apennine sedimentary sequences, geoarchaeo...
Long-term climatic trends of the Paleogene were interrupted by global perturbations of the carbon cycle, commonly associated with warming of surface and bottom waters and ecosystem disturbance. Most of these perturbations occurred in the Paleocene - Eocene greenhouse climate, but others were superimposed on the transition of greenhouse-to- icehouse...
Benthic foraminiferal surface porosity (the mean percentage of surface area covered by pores; higher porosity: lower oxygenation) and iodine to calcium ratio (I/Ca, higher I/Ca: higher oxygenation) are both promising paleoceanographic proxies that will advance through testing in down-core studies. Here we report the first down-core comparison (~45...
The Paleogene was punctuated by perturbations of the global carbon cycle, many associated with transient global warming events (hyperthermals). The Dan-C2 event (~160 kyr after Cretaceous/Paleogene boundary; K/Pg) was the oldest of these eccentricity-linked carbon cycle disturbances (ELCD). In contrast to other hyperthermals, the Dan-C2 event was n...
Under stress, corals and foraminifera may eject or consume their algal symbionts (“bleach”), which can increase mortality. How bleaching relates to species viability over warming events is of great interest given current global warming. We use size-specific isotope analyses and abundance counts to examine photosymbiosis and population dynamics of p...
All studies focused on the evaluation of paleoecological variability over geological time must be linked to a specific age or time interval, which can be defined using different time scales (biostratigraphic, chronostratigraphic, geochronological or orbital). Therefore, integrated time scales are essential to allow comparisons of data from differen...
Benthic foraminifera are the most common meiofaunal unicellular deep-sea biota, forming skeletons used as proxies for past climate change. We aim to increase understanding of past non-analog oceans and ecosystems by evaluating deep-sea benthic foraminiferal responses to global environmental changes over latest Cretaceous through Oligocene times (67...
How oxygen levels in Earth’s atmosphere and oceans evolved has always been a central question in Earth System Science. Researchers have developed numerous tracers to tackle this question, utilizing geochemical characteristics of different elements. Iodine incorporated in calcium carbonate (including biogenic) minerals, reported as I/Ca, is a proxy...
Significance
During the Eocene, high-latitude regions were much warmer than today and substantial polar ice sheets were lacking. Indeed, the initiation of significant polar ice sheets near the end of the Eocene has been closely linked to global cooling. Here, we examine the relationship between global temperatures and continental-scale polar ice sh...
We reconstruct sea surface temperatures (SSTs) at Deep Sea Drilling Project Site 608 (42.836°N, 23.087°), north of the Azores Front, and Ocean Drilling Program Site 982 (57.516°N, 15.866°), under the North Atlantic Current, in order to track Miocene (23.1–5.3 Ma) development of North Atlantic surface waters. Mean annual SSTs from TEX86 and UK′37 pr...
The decline in dissolved oxygen in global oceans (ocean deoxygenation) is a potential consequence of global warming which may have important impacts on ocean biogeochemistry and marine ecosystems. Current climate models do not agree on the trajectory of future deoxygenation on different timescales, in part due to uncertainties in the complex, linke...
An impact with a dash of volcanism
Around the time of the end-Cretaceous mass extinction that wiped out dinosaurs, there was both a bolide impact and a large amount of volcanism. Hull et al. ran several temperature simulations based on different volcanic outgassing scenarios and compared them with temperature records across the extinction event. Th...
Significance
Debate lingers over what caused the last mass extinction 66 million years ago, with intense volcanism and extraterrestrial impact the most widely supported hypotheses. However, without empirical evidence for either’s exact environmental effects, it is difficult to discern which was most important in driving extinction. It is also uncle...
Profound changes in upper ocean oxygenation have taken place in recent decades and are expected to continue in the future, but the complexity of the processes driving these changes has yet to be fully unraveled. Planktic foraminiferal I/Ca is a promising tool to reconstruct the extent of past upper ocean oxygenation, but a thorough assessment is ne...
Our understanding of the long‐term evolution of the Earth system is based on the assumption that terrestrial weathering rates should respond to, and hence help regulate, atmospheric CO2 and climate. Increased terrestrial weathering requires increased carbonate accumulation in marine sediments, which in turn is expected to result in a long‐term deep...
Climate change is predicted to alter temperature, carbonate chemistry and oxygen availability in the oceans, which will affect individuals, populations and ecosystems. We use the fossil record of benthic foraminifers to assess developmental impacts in response to environmental changes during the Palaeocene–Eocene Thermal Maximum (PETM). Using an un...
We combine stable isotope, calcareous nannoplankton, and benthic foraminiferal records for Ocean Drilling Program Sites 1262 (paleodepth ~3,500 m) and 1263 (paleodepth ~1,500 m) on Walvis Ridge (SE Atlantic), to document the marine biotic response to Eocene Thermal Maximum 3, in the early part of the Early Eocene Climate Optimum, ~3.1 Myr after the...
Rising oceanic and atmospheric oxygen levels through time have been crucial to enhanced habitability of surface Earth environments. Few redox proxies can track secular variations in dissolved oxygen concentrations ([O2]) around threshold levels for metazoan survival in the upper ocean. We present an extensive compilation of iodine to calcium ratios...
Climate proxies indicate coupling between changes in atmospheric pCO2, global temperatures, and ice volume over much of the Cenozoic. Evidence has been presented for decoupling of these factors in the Miocene, though the cause of the apparent decoupling was uncertain. Here, we revisit Deep Sea Drilling Program (DSDP) Site 608 (24-9 Ma) in the North...
The early Eocene greenhouse world was marked by multiple transient hyperthermal events. The most extreme was the Paleocene-Eocene Thermal Maximum (PETM, ~56 Ma), linked to the extinction of the globally recognised deep-sea benthic foraminiferal Velasco fauna, which led to the development of early Eocene assemblages. This turnover has been studied a...
Taxonomic list.
Most common benthic foraminifera during the early Eocene and other species mentioned in the text.
(DOCX)
Quantitative data of benthic foraminifera in the studied samples from ODP Site 1051 and 1258.
(XLSX)
Benthic foraminifera across the middle Ypresian interval.
(XLSX)
Number of species vs. number of specimens in samples from ODP Sites 1051 and 1258.
(TIF)
Quantitative data of benthic foraminifera in the studied samples from DSDP site 401.
(XLSX)
Benthic foraminifera across the lower Ypresian interval.
(XLSX)
Quantitative data of benthic foraminifera in the studied samples from ODP Site 1262 and 1263.
(XLSX)
Number of samples, specimens and species, and size fraction studied in each site.
(XLSX)
The Palaeocene–Eocene Thermal Maximum1, 2 (PETM) was a global warming event that occurred about 56 million years ago, and is commonly thought to have been driven primarily by the destabilization of carbon from surface sedimentary reservoirs such as methane hydrates3. However, it remains controversial whether such reservoirs were indeed the source o...
The temperature of the deep ocean plays a vital role in the Earth’s climate system. Paleo-reconstructions of deep-sea temperatures have traditionally been based on the oxygen isotope composition of deep-sea benthic foraminiferal calcite shells, although this parameter depends upon polar ice volume as well as temperature. More recent reconstructions...
The geological cycling of carbon ties together the ocean-Atmosphere carbon pool, Earth's biosphere, and Earth's sedimentary reservoirs. Perturbations to this coupled system are recorded in the carbon-isotopic (δ¹³C) composition of marine carbonates. Large amplitude δ¹³C excursions are typically treated as individual events and interpreted according...
The Editor-in-Chief of Paleoceanography explains that the journal is changing its name to Paleoceanography and Paleoclimatology to reflect the evolution of science in this field.
A collection of Commentaries published in the journals of the American Geophysical Union illuminate the deep and growing benefits of research in the Earth and space sciences for humanity.
A holistic view of the Bengal–Nicobar Fan system requires sampling the full sedimentary section of the Nicobar Fan, which was achieved for the first time by International Ocean Discovery Program (IODP) Expedition 362 west of North Sumatra. We identified a distinct rise in sediment accumulation rate (SAR) beginning ∼9.5 Ma and reaching 250–350 m/Myr...
Benthic foraminiferal biofacies were delimited for the upper Maastichtian through upper Eocene of five Brazilian marginal basins (Sergipe-Alagoas, Mucuri, Campos, Santos and Pelotas) and two DSDP Sites 356 and 20C of the western South Atlantic. The biofacies were determined based on the benthic foraminiferal assemblages and associated parameters, i...
Newberry Volcano in Oregon, USA, has two small crater lakes inside its caldera: East Lake and Paulina Lake. The 50-80 m deep lakes differ in morphology, water chemistry and sediment composition, although separated only by a narrow volcanic ridge. East Lake is a terminal lake with gaseous geothermal inputs, whereas Paulina Lake has an outlet (Paulin...
Anthropogenic warming could well drive depletion of oceanic oxygen in the future. Important insight into the relationship between de-oxygenation and warming can be gleaned from the geological record, but evidence is limited because few ocean oxygenation records are available for past greenhouse climate conditions. We use I/Ca in benthic foraminifer...
Oxygen depletion in the upper ocean is commonly associated with poor ventilation and storage of respired carbon, potentially linked to atmospheric CO2 levels. Iodine to calcium ratios (I/Ca) in recent planktonic foraminifera suggest that values less than ∼2.5 μmol mol-1 indicate the presence of O2-depleted water. Here we apply this proxy to estimat...
We investigated the response of late Paleocene-middle Eocene (~60-37.5 Ma) benthic foraminiferal assemblages to long term climate change and hyperthermal events including the Paleocene-Eocene Thermal Maximum (PETM) at ODP Site 865 on Allison Guyot, a seamount in the Mid-Pacific Mountains. Seamounts are isolated deep-sea environments where enhanced...
The Forada section (northeastern Italy) provides a continuous, expanded deep-sea record of the Paleocene–Eocene Thermal Maximum (PETM) in the central-western Tethys. We combine a new, high-resolution, benthic foraminiferal assemblage record with published calcareous plankton, mineralogical and biomarker data to document climatic and environmental c...
Morphologically uniform, low-trochospiral foraminifera are a common, though not very well-preserved component of foraminiferal assemblages across the interval including the Middle Eocene Climatic Optimum (MECO) at the Alano (northeastern Italy) and Monte Cagnero (central Italy) Tethyan sections. The morphology of these specimens, combined with thei...
Synchrotron powder X-ray diffraction and scanning electron microscopy examinations of manganese oxide concretions/nodules
(~0.3–1.0 mm diameter) from ODP Site 1262 on Walvis Ridge in the Southeastern Atlantic Ocean revealed that they consist primarily
of the layered Mn oxide phase jianshuiite [(Mg,Mn,Ca)Mn34+O7·3H2O]. The nodules are from an interv...
Foraminifera are important microfossils used in analysis of paleoclimates and paleoenvironments. Examining their ontogeny (including size of the protoconch) and growth rates can provide insight into their ecology and life history, e.g., food supply in the environments where they lived. In planktic taxa, shifts in habitat (e.g., moving to deeper wat...
In modern oceans, temperature stress can cause symbiont-bearing taxa, like corals and sponges, to expel their photosymbionts in ‘bleaching’ events that can be lethal. Whether or not symbiotic clades will be able to adapt to elevated temperatures for the coming millennia is hard to predict from empirical observations of living taxa alone. Instead, p...
The response of many organisms to the Paleocene-Eocene Thermal Maximum (PETM; ~56 Ma) has been documented, but marine mollusks are not known from any deposits of that age. For the first time, we describe a PETM assemblage of pteropods (planktic mollusks), consisting of six species representing three genera ( Altaspiratella, Heliconoides and Limacin...
Antarctic continental-scale glaciation is generally assumed to have initiated at the Eocene-Oligocene Transition, yet its subsequent evolution is poorly constrained. We reconstruct changes in bottom water temperature and global ice volume from 0-17 Ma using δ18O in conjunction with Mg/Ca records of the infaunal benthic foraminifer, O. umbonatus fro...
The biotic response of calcareous nannoplankton
to environmental and climatic changes during the Eocene–
Oligocene transition was investigated at a high resolution at
Ocean Drilling Program (ODP) Site 1263 (Walvis Ridge,
southeast Atlantic Ocean) and compared with a lowerresolution benthic foraminiferal record. During this time interval, global cli...
N.B. This is the paper under (open) review on Climate of the Past DISCUSSION. The final, fully citable and published version is: Giusberti L., Boscolo Galazzo F., Thomas E., 2016. Variability in climate and productivity during the Paleocene–Eocene Thermal Maximum in the western Tethys (Forada section). Climate of the Past 12(2): 213-240, DOI: 10.51...
Eocene Thermal Maximum 2 (ETM2) occurred ~1.8 Myr after the Paleocene-Eocene Thermal Maximum (PETM) and, like the PETM, was characterized by a negative carbon isotope excursion and warming. We combined benthic foraminiferal and sedimentological records for Southeast Atlantic Sites 1263 (1500 m paleodepth) and 1262 (3600 m paleodepth) to show that b...
The biotic response of calcareous nannoplankton to environmental and climatic changes during the Eocene–Oligocene transition (~34.8–32.7 Ma) was investigated at high resolution at Ocean Drilling Program (ODP) Site 1263 (Walvis Ridge, South East Atlantic Ocean), and compared with a lower resolution benthic foraminiferal record. During this time inte...
During the Eocene-Oligocene transition (EOT), the world changed from a high-pCO 2 warm Eocene world to a cool, lower pCO 2 Oligocene world, oceanic phytoplankton was affected in various ways (Persico & Villa, 2004; Dunkley Jones et al., 2008; Henderiks & Pagani, 2008). To unravel the relations between changes in climatic and calcareous nannofossil...
The environmental impact of the Paleocene-Eocene Thermal Maximum (PETM) has been intensively studied in the New Jersey Coastal Plain, but the benthic foraminiferal response, reflecting bottom water conditions, has not been documented at high resolution. We use benthic foraminiferal data across the Paleocene-Eocene boundary in cores from Wilson Lake...
The onset of the Paleocene/Eocene thermal maximum (PETM) and associated carbon isotope excursion (CIE; about 56 million years ago) was geologically abrupt but it is debated whether it took thousands of years or was effectively instantaneous. A significant new record of the onset of the CIE was published by Wright and Schaller (2013) who claimed tha...
During the Eocene-Oligocene transition (EOT, ca. 34 Ma), Earth's climate cooled significantly from a greenhouse to an icehouse climate, while the calcite (CaCO3) compensation depth (CCD) in the Pacific Ocean increased rapidly. Fluctuations in the CCD could result from various processes that create an imbalance between calcium (Ca) sources to, and s...
Eocene Thermal Maximum 2 (ETM2) occurred ~1.8 Myr after the Paleocene Eocene Thermal Maximum (PETM) and, like the PETM, was characterized by a negative carbon isotope excursion coupled with warming. We combined benthic foraminiferal and sedimentological records for Southeast Atlantic Sites 1263 (1500 m paleodepth) and 1262 (3600 m paleodepth) to sh...
Text: The Middle Eocene Climatic Optimum (MECO; ~40 Ma) stands out as a middle-term (~500 kyr) interval of warming, interrupting the long-term cooling starting in the latest early Eocene. To characterize oceanographic and biotic changes related to the MECO, we performed a multiproxy investigation at Site 1263 (Walvis Ridge; 28°31.98′S, 02°46.77′E,...
The Middle Eocene Climatic Optimum (MECO, ~40 Ma) was a transient period of global warming that interrupted the secular Cenozoic cooling trend. We investigated the paleoceanographic, paleoenvironmental and paleoecological repercussions of the MECO in the south-east Atlantic subtropical gyre (Ocean Drilling Program Site 1263). TEX86 and δ18O records...
Many compelling management issues in Long Island Sound (LIS) focus on how organisms respond to stresses such as commercial and recreational harvesting, eutrophication, hypoxia, habitat degradation, invasion of non-native species, ocean acidification, and climate change. In order to address these complex problems, we must first understand the factor...
Paleocene-Eocene benthic foraminifera were studied in the western South Atlantic in samples from industry cores and well cuttings from Brazilian marginal basins (Sergipe-Alagoas, Bahia-Sul, Campos, Santos and Pelotas) and cores from DSDP Leg 39 Site 356 (São Paulo Plateau) and Leg 3 Site 20C (Rio Grande Rise) in order to recognize benthic foraminif...
Anthropogenic global warming affects marine ecosystems in complex ways, and declining ocean oxygenation is a growing concern. Forecasting the geographical and bathymetric extent, rate and intensity of future deoxygenation and its effects on oceanic biota, however, remains highly challenging because of the complex feedbacks in the earth-ocean-biota...