Forcing mechanisms for mid-Cretaceous black shale formation: evidence from the Upper Aptian and Lower Albian of the Vocontian Basin (SE France)


Herrle, J.O., Pross, J., Friedrich, O., Kößler, P. and Hemleben, C. (2003) Forcing mechanisms for mid-Cretaceous black shale formation: evidence from the Upper Aptian and Lower Albian of the Vocontian Basin (SE France). Palaeogeography, Palaeoclimatology, Palaeoecology, 190, 399-426. (doi:10.1016/S0031-0182(02)00616-8).

Download

Full text not available from this repository.

Original Publication URL: doi:10.1016/S0031-0182(02)00616-8

Description/Abstract

Calcareous nannoplankton, palynomorph, benthic foraminifera, and oxygen isotope records from the supraregionally distributed Niveau Paquier (Early Albian age, Oceanic Anoxic Event 1b) and regionally distributed Niveau Kilian (Late Aptian age) black shales in the Vocontian Basin (SE France) exhibit variations that reflect paleoclimatic and paleoceanographic changes in the mid-Cretaceous low latitudes. To quantify surface water productivity and temperature changes, nutrient and temperature indices based on calcareous nannofossils were developed. The nutrient index strongly varies in the precessional band, whereas variations of the temperature index reflect eccentricity. Since polar ice caps were not present during the mid-Cretaceous, these variations probably result from feedback mechanisms within a monsoonal climate system of the mid-Cretaceous low latitudes involving warm/humid and cool/dry cycles. A model is proposed that explains the formation of mid-Cretaceous black shales through monsoonally driven changes in temperature and evaporation/precipitation patterns. The Lower Albian Niveau Paquier, which has a supraregional distribution, formed under extremely warm and humid conditions when monsoonal intensity was strongest. Bottom water ventilation in the Vocontian Basin was diminished, probably due to increased precipitation and reduced evaporation in regions of deep water formation at low latitudes. Surface water productivity in the Vocontian Basin was controlled by the strength of monsoonal winds. The Upper Aptian Niveau Kilian, which has a regional distribution only, formed under a less warm and humid climate than the Niveau Paquier. Low-latitude deep water formation was reduced to a lesser extent and/or on regional scale only. The threshold for the formation of a supraregional black shale was not reached. The intensity of increases in temperature and humidity controlled whether black shales developed on a regional or supraregional scale. At least in the Vocontian Basin, the increased preservation of organic matter at the sea floor was more significant in black shale formation than the role of enhanced productivity.

Item Type: Article
ISSNs: 0031-0182 (print)
Related URLs:
Keywords: black shale; Cretaceous; benthic foraminifera; calcareous nannofossils; palynomorphs; monsoon
Subjects: Q Science > QE Geology
G Geography. Anthropology. Recreation > GC Oceanography
Divisions: University Structure - Pre August 2011 > School of Ocean & Earth Science (SOC/SOES)
ePrint ID: 49995
Date Deposited: 08 Jan 2008
Last Modified: 27 Mar 2014 18:33
URI: http://eprints.soton.ac.uk/id/eprint/49995

Actions (login required)

View Item View Item