Geology topics

Tali Babila

Publications and source records attributed to Tali Babila.

4 recordsLinked to original sources

USGS2024

Paleogene Earth perturbations in the US Atlantic Coastal Plain (PEP-US): Coring transects of hyperthermals to understand past carbon injections and ecosystem responses

The release of over 4500 Gt (gigatonnes) of carbon at the Paleocene–Eocene boundary provides the closest geological analog to modern anthropogenic CO 2 emissions. The cause(s) of and responses to the resulting Paleocene–Eocene Thermal Maximum (PETM) and attendant carbon isotopic excursion (CIE) remain enigmatic and intriguing despite over 30 years of intense study. CIE records from the deep sea are generally thin due to its short duration and slow sedimentation rates, and they are truncated due to corrosive bottom waters dissolving carbonate sediments. In contrast, PETM coastal plain sections along the US mid-Atlantic margin are thick, generally having an expanded record of the CIE. Drilling here presents an opportunity to study the PETM onset to a level of detail that could transform our understanding of this important event. Previous drilling in this region provided important insights, but existing cores are either depleted or contain stratigraphic gaps. New core material is needed for well-resolved marine climate records. To plan new drilling, members of the international scientific community attended a multi-staged, hybrid scientific drilling workshop in 2022 designed to maximize not only scientifically and demographically diverse participation but also to protect participants' health and safety during the global pandemic and to reduce our carbon footprint. The resulting plan identified 10 sites for drill holes that would penetrate the Cretaceous–Paleogene (K–Pg) boundary, targeting the pre-onset excursion (POE), the CIE onset, the rapidly deposited Marlboro Clay that records a very thick CIE body, and other Eocene hyperthermals. The workshop participants developed several primary scientific objectives related to investigating the nature and the cause(s) of the CIE onset as well as the biotic effects of the PETM on the paleoshelf. Additional objectives focus on the evidence for widespread wildfires and changes in the hydrological cycle, shelf morphology, and sea level during the PETM as well as the desire to study both underlying K–Pg sediments and overlying post-Eocene records of extreme hyperthermal climate events. All objectives address our overarching research question: what was the Earth system response to a rapid carbon cycle perturbation?

Scientific Drilling↗

USGS2022

Shelf ecosystems along the U.S. Atlantic Coastal Plain prior to and during the Paleocene-Eocene Thermal Maximum: Insights into the stratigraphic architecture

The Paleocene-Eocene Thermal Maximum (PETM) is the most pronounced global warming event of the early Paleogene related to atmospheric CO 2 increases. It is characterized by negative δ 18 O and δ 13 C excursions recorded in sedimentary archives and a transient disruption of the marine biosphere. Sites from the U.S. Atlantic Coastal Plain show an additional small, but distinct δ 13 C excursion below the onset of the PETM, coined the “pre-onset excursion” (POE), mimicking the PETM-forced environmental perturbations. This study focuses on the South Dover Bridge core in Maryland, where the Paleocene-Eocene transition is stratigraphically constrained by calcareous nannoplankton and stable isotope data, and in which the POE is well-expressed. The site was situated in a middle neritic marine shelf setting near a major outflow of the paleo-Potomac River system. We generated high-resolution benthic foraminiferal assemblage, stable isotope, trace-metal, grain-size and clay mineralogy data. The resulting stratigraphic subdivision of this Paleocene-Eocene transition is placed within a depth transect across the paleoshelf, highlighting that the PETM sequence is relatively expanded. The geochemical records provide detailed insights into the paleoenvironment, developing from a well-oxygenated water column in latest Paleocene to a PETM-ecosystem under severe biotic stress-conditions, with shifts in food supply and temperature, and under dysoxic bottom waters in a more river-dominated setting. Environmental changes started in the latest Paleocene and culminated atthe onset of the PETM, hinting to an intensifying trigger rather than to an instantaneous event at the Paleocene-Eocene boundary toppling the global system.

Delaware, Maryland, New Jersey, Pennsylvania, Virg↗

USGS2019

The planktonic foraminiferal response to the Paleocene-Eocene thermal maximum on the Atlantic coastal plain

Planktonic foraminiferal assemblages in two cores from Maryland and New Jersey show evidence for significant changes in surface ocean habitats on the continental shelf during the Paleocene-Eocene Thermal Maximum (PETM). At both sites, significant assemblage shifts occur immediately before the onset of the event. These changes include the appearance of abundant triserial/biserial species as well as rare excursion taxa, which are limited to the interval of the carbon isotope excursion at deep-sea sites. The assemblage shifts signal the development of new habitats immediately prior to the onset of the PETM, likely involving warming, surface ocean acidification, increased stratification and oligotrophy. A sharp increase in diversity at the onset of the event is interpreted as a further increase in stratification and warming, as well as increased water depth and more eutrophic conditions. Finally, we observe variant morphologies of several planktonic foraminifera, which may also signal the response of the assemblage to environmental perturbation.

Atlantic coastal plain↗

USGS2018

Evidence for shelf acidification during the onset of the Paleocene-Eocene Thermal Maximum

A transect of paleoshelf cores from Maryland and New Jersey contains a ~0.19 m to 1.61 m thick interval with reduced percentages of carbonate during the onset of the Paleocene-Eocene Thermal Maximum (PETM). Outer paleoshelf cores are barren of nannofossils and correspond to two minor disconformities. Middle paleoshelf cores contain a mixture of samples devoid of nannofossils and those with rare specimens characterized by significant dissolution (i.e., etching). The magnitude of the decrease in carbonate cannot be explained by dilution by clastic material or dissolution resulting from the oxidation of organic matter during early diagenesis. The observed preservation pattern implies a shoaling of the calcite compensation depth (CCD) and lysocline to the middle shelf. This reduced carbonate interval is observed during the onset of the PETM on other continental margins raising the possibility that extreme shoaling of the CCD and lysocline was a global signal which is more significant than in previous estimates for the PETM. An alternative scenario is that shoaling was restricted to the northwest Atlantic, enhanced by regional and local factors (eutrophication from rivers, microbial activity associated with warming) that exacerbated the impact of acidification on the shelf.

Maryland, New Jersey↗