Paleoceanographic, and paleoclimatic constraints on the global Eocene diatom and silicoflagellate record

Palaeogeography, Palaeoclimatology, Palaeoecology
By: , and 

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Abstract

Eocene diatom and silicoflagellate biostratigraphy are summarized and correlated with the most recent geologic time scale as well as with the global oxygen isotope and eustatic sea level curves. The global distribution of Eocene diatom/silicoflagellate-bearing sediments varies considerably, reflecting changing oceanic gateways and paleoceanography with changing patterns that are punctuated by four major depositional events.

Event 1 (~ 49 million years ago, Ma), at the end of the Early Eocene Climatic Optimum (EECO), saw the cessation of diatom/silicoflagellate deposition in epicontinental regions of the North Sea region and in the northern Russia and the onset of biosilica deposition in the Arctic. Event 2 (~ 46 Ma), which coincided with intensification of the Middle Eocene cooling trend, marked the widespread expansion of diatom/silicoflagellate deposition in both the North and South Atlantic. A shift of diatom/silicoflagellate deposition from the Atlantic to the Pacific began at Event 3, at the end of the Middle Eocene Climatic Optimum (MECO) (~ 40 Ma), that was likely tied to the initial opening of the Drake Passage between Antarctica and South America. Event 4 (~ 39 Ma) coincided with a major sea level fall and a widespread deep-sea hiatus in the latest Middle Eocene. Late Eocene diatom/silicoflagellate deposition became more concentrated in middle-to-high latitude regions and coastal upwelling regions, particularly in the Pacific Ocean.

Tabulation of the first and last occurrences of 132 biostratigraphically-important diatoms suggests increased species turnover during the latest Paleocene to earliest Eocene that may be in part due to a monographic effect. An increasing rate of evolution of new diatom species between ~ 46 and 43 Ma and after ~ 40 Ma coincides respectively with the widespread expansion of diatom deposition in the Atlantic and with an increased pole-to-equator thermal gradient that witnessed the expansion of diatoms in high latitude oceans and coastal upwelling settings.

Additional publication details

Publication type Article
Publication Subtype Journal Article
Title Paleoceanographic, and paleoclimatic constraints on the global Eocene diatom and silicoflagellate record
Series title Palaeogeography, Palaeoclimatology, Palaeoecology
DOI 10.1016/j.palaeo.2015.01.015
Volume 422
Year Published 2015
Language English
Publisher Elsevier
Contributing office(s) Volcano Science Center
Description 16 p.
First page 85
Last page 100
Other Geospatial Earth
Online Only (Y/N) N
Additional Online Files (Y/N) N