Examining the Impacts of Oxygen and Carbon System Variability on Fossil Benthic Foraminiferal Shell Weight
Abstract
Foraminiferal shell weight can be impacted by environmental factors both during initial shell formation and as the result of post mortem preservation. An improved understanding of what determines this relationship can lead to both an understanding of foraminiferal calcite production in modern oceans and proxy development for past environmental conditions. Significantly, foraminiferal shell weight has been linked to carbonate ion concentration in both laboratory culture (of both planktic and benthic species) and in the modern and fossil record (in planktic foraminifera). This study explores the relationship between shell weight and changes in oxygenation and carbonate saturation in fossil benthic foraminifera from a high-resolution sedimentary record (MV0811-15JC; 34°36.930' N, 119°12.920' W; 418m water depth; 16.1-3.4 ka; sedimentation rate 44-100 cm kyr-1) from Santa Barbara Basin, CA (SBB). Ongoing work in SBB has described rapid biotic reorganization through the recent deglaciation in response to changes in dissolved oxygen concentrations, which are used here to create a semi quantitative oxygenation history for site MV0811-15JC. In modern Oxygen Minimum Zones, decreases in oxygen closely covary with increases in Total Carbon (with a corresponding decrease in the carbonate saturation state). We interpret that records from SBB of the average size-normalized test weight of Uvigerinid and Bolivinid foraminifera show that shell weight responds to these changes in oxygenation and saturation state. Multiple metrics of 'size normalization' including by length, geometric estimation of surface area and volume, and tracing of individual silhouettes are tested. Regardless of method utilized, the size normalized shell weight of all species fluctuates with abrupt changes in oxygenation and saturation state. Although all species respond to large-scale environmental changes, the weight records of Bolivinids and Uvigerinids reveal distinct differences, indicating that processes governing shell weight may vary across taxonomic groups.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2013
- Bibcode:
- 2013AGUFMPP23B1954D
- Keywords:
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- 0459 BIOGEOSCIENCES Macro- and micropaleontology;
- 0473 BIOGEOSCIENCES Paleoclimatology and paleoceanography;
- 4944 PALEOCEANOGRAPHY Micropaleontology;
- 0404 BIOGEOSCIENCES Anoxic and hypoxic environments