The planktonic foraminiferal response to the Paleocene Eocene Thermal Maximum on the Atlantic Coastal Plain

Open Access
Author:
Livsey, Caitlin Marie
Graduate Program:
Geosciences
Degree:
Master of Science
Document Type:
Master Thesis
Date of Defense:
July 20, 2015
Committee Members:
  • Timothy Bralower, Thesis Advisor
Keywords:
  • planktonic foraminifera
  • excursion taxa
  • PETM
Abstract:
Cores on the Atlantic Coastal Plain contain an expanded record of the onset of the Paleocene Eocene Thermal Maximum (PETM), an abrupt global warming event occurring 55 mya. Though a seemingly well-studied event, details about what exactly occurred during the PETM are still lacking due to differential local effects, absence of precise time resolution, and considerable dissolution of deep sea carbonates at the onset of the event. Here we present high-resolution planktonic foraminiferal assemblage data from cores from Maryland and New Jersey that show significant changes in surface ocean habitats immediately before and during the onset of the event. Assemblages immediately below the PETM show evidence for environmental stress including oligotrophy, while marked changes in assemblages at the onset of the event reflect an increase in stratification. An anomalously high abundance of the stress indicating triserial/biserial planktonic foraminifera in the late Paleocene support the increase in environmental stress directly prior to the event on the coastal plain. We observe Acarinina sibaiyaensis, a species previously thought to have originated during the PETM, below the event at both sites. The appearance of A. sibaiyaensis prior to the PETM in the Atlantic Coastal Plain suggests that it evolved on the shelf in response to oligotrophy and tracked these conditions to the open ocean during the event. Planktonic foraminifera diversified on the shelf during the PETM likely due to a combination of sea level rise, warming of the coastal waters, and consequent increased stratification, which provided new habitats. We present the occurrence of variant morphologies of several planktonic foraminifera near the peak of the carbon isotope excursion at Bass River, which may signal the response of the assemblage to environmental perturbation. These high-resolution records of planktonic foraminifera from before and during the onset of the PETM offer insights into how the local environment shifted across the event, and what that meant for the evolution of Acarinina sibaiyaensis.