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- Title
Black shales contamination and depositional paleoenvironment during the Early Aptian OAE 1a in the Eastern Russian Platform.
- Authors
ZORINA, SVETLANA O.
- Abstract
The most pernicious consequences of the Early Aptian Oceanic Anoxic Event (OAE) 1a in the North-Eastern Peri- Tethys for benthic microfauna were oxygen decrease and the onset of sulphidic conditions, related to toxic enrichment in heavy metals which can be regarded as one of the main causes for biota distress and even their disappearance. Twenty-nine samples from the Tatar-Shatrashany borehole located in the Ulyanovsk-Saratov Trough (Eastern Russian Platform) were studied to estimate the extent of anoxia using trace element redox proxies and pyrite framboid morphology and distribution. The degree of contamination in toxic metals (As, Cd, Se, Pb, Zn, Ni, Mo, Cu, V, and W) is estimated for the Lower Aptian OAE 1a-related black shales of the Ulyanovsk Formation and compared with the results obtained for the Late Jurassic OAE-related black shales of the Promzino Formation and host mudrocks. The relationships between benthic foraminiferal abundance and diversity and black shales contamination in toxic metals are evaluated. Extreme contamination of the OAE 1a-related black shales in Mo and Cd in conjunction with the absence of oxygen could result in conditions not suitable for benthic foraminifers dwelling. The key species Mjatliukaena aptiensis (Mjatl.) is regarded to be one of the toxic-resistant species that successfully recovered from the OAE 1a anoxic stress. Comparing to the Late Jurassic OAE, the integrated data indicate moderately contaminated black shales and mainly dysoxic conditions under which habitat conditions were not completely detrimental for benthic foraminifers. The most toxic-resistant species was Lenticulina infravolgaensis (Furs. et Pol.).
- Subjects
BLACK shales; MUDSTONE; COPPER; TRACE elements; HYPOXEMIA; BIOTIC communities; HEAVY metals
- Publication
Bulletin of Geosciences, 2022, Vol 97, Issue 1, p123
- ISSN
1214-1119
- Publication type
Article
- DOI
10.3140/bull.geosci.1800