ECOLOGICAL CHANGES IN THE NANNOPLANKTON COMMUNITY ACROSS A SHELF TRANSECT DURING THE ONSET OF THE PALEOCENE-EOCENE THERMAL MAXIMUM

Open Access
Author:
Leon y Leon, Isabel Aurora
Graduate Program:
Geosciences
Degree:
Master of Science
Document Type:
Master Thesis
Date of Defense:
December 08, 2016
Committee Members:
  • Timothy Bralower, Thesis Advisor
  • Lee Kump, Committee Member
  • Mark Patzkowsky, Committee Member
Keywords:
  • nannoplankton
  • PETM
  • Paleocene-Eocene Thermal Maximum
  • nearshore
  • paleoecology
  • Cambridge-Dorchester MD
  • shelf environment
Abstract:
Warming and other environmental changes during the Paleocene-Eocene Thermal Maximum (PETM) led to profound shifts in the composition and structure of nannoplankton assemblages. Here we analyze the nature of these changes in an expanded shelf record from the Cambridge-Dorchester (CamDor) section in Maryland. There are three shifts observed in the CamDor assemblages which represent changes in the environment. We interpret these changes using a combination of published paleoecology and nonmetric multidimensional scaling (NMS). The first shift involves a sharp increase in the abundance of Hornibrookina and a decrease in Toweius coincident with the pre-onset carbon isotope excursion (POE) and is interpreted to represent increased surface ocean productivity. The second shift just below the prominent dissolution interval involves a sharp increase in the abundance of Discoaster, Fasciculithus and Coccolithus and a decrease in the abundance of Hornibrookina and is interpreted to represent a combination of warming and decreased productivity. The third shift immediately above the dissolution interval involves a substantial change in the whole assemblage and is thought to represent the major phase of PETM warming. Cluster analysis indicates that the structure of nannoplankton assemblage changed significantly across the dissolution interval. NMS analysis of samples from sections from Maryland and New Jersey suggest a decrease in productivity from the inner to the outer shelf at the onset of the PETM.