Holocene Benthic Foraminifera Distribution: Paleoclimatic and Paleoceanographic Records in Anoxic Basins along the British Columbia Coast
Lamidi Olabode Babalola
Earth Sciences Department Carleton University Ottawa, Ontario Canada
E-mail: [email protected]
Paleoclimatic and paleoceanographic changes in the last 5000 years, archived in three glacier-carved fjords in the Seymour-Belize Inlet Complex, British Columbia coast are investigated. Foraminiferal, sedimentological and geochemical proxies are utilized in this study. The fjords’ sediments are dominantly organically rich mud and silts with occasional sand intervals deposited as annually laminated, massive, slump or graded units.
Low faunal diversity, abundances, and low Shannon Diversity Index indicate highly stressed, anoxic and unfavourable environmental settings in the inlets. Agglutinated foraminifera and thecamoebians dominate the faunal assemblages in piston cores while calcareous foraminifera are dominant in freeze cores. Five biofacies are identified. These are Biofacies 1 (very abundant Eggerella advena); and Biofacies 2 (slightly reduced Eggerella advena; Recurvoides tubinatus and Spiroplectammina biformis increased). Biofacies 3, subdivided into: Biofacies 3a (dominant Recurvoides tubinatus and Spiroplectammina biformis; much reduced Eggerella advena); Biofacies 3b (decreased Eggerella advena, Spiroplectammina biformis and Recurvoides tubinatus; abundant thecamoebians); and Biofacies 3c (abundant Eggerella advena; fairly represented Recurvoides tubinatus and Spiroplectammina biformis). Others are Biofacies 4 (very abundant thecamoebians, low foraminifera); and Biofacies 5 (very abundant calcareous Buccella frigida and Cibroelphidium excavata).
High temperature, low salinity and low oxygen conditions influence the thecamoebian dominated biofacies. The presence of glaciomarine agglutinated foraminifera (Spiroplectammina biformis, Recurvoides tubinatus, Portatrochammina bipolaris and Haplophragmoides bradyi) in biofacies 1 to 3, suggests a relatively cool, moderately saline, and suboxic environmental setting. Biofacies 5 represents a low temperature, saline, well ventilated environment. The final report will contain results of the ongoing geochemical aspects of this research.
AAPG Search and Discovery Article #90070 © 2007 AAPG Foundation Grants in Aid