TITLE:
Multiple Proxies on the Paleoenvironment of the Early Cambrian Marine Black Rock Series in the Tarim Basin, NW China: Molybdenum Isotope and Trace Element Evidence
AUTHORS:
Chunyan Yao, Weimin Guo, Junan Liu, Hanwu Li
KEYWORDS:
Molybdenum Isotope, Trace Element, Paleo-Environment, Early Cambrian, Tarim Basin
JOURNAL NAME:
International Journal of Geosciences,
Vol.8 No.8,
August
21,
2017
ABSTRACT: The early Cambrian carbonaceous shale and laminated chert-phosphorite assemble
(the black rock series) are widespread at the northwest margin of the
Tarim Basin, Northwest China. In combination with previously reported data,
we present stable molybdenum isotope (δ98/95Mo), TOC, and redox-sensitive
trace elements to evaluate the sedimentary conditions in early Cambrian water
column during the deposition of the black rock series in the Tarim Basin.
Redox variation was documented based on enrichment factors (MoEF, VEF, and
UEF) and redox-sensitiv elements ratios (Ni/Co, V/Cr, δU), etc. During the
early Cambrian, there was transgressive event, and the sea level continues to
rise. In the basal Cambrian, laminated chert-phosphorite assemble with low
TOC concentrations suggest the oxic sedimentary condition in a restricted
basin. Light Mo isotope values and redox sensitive elements enrichment in the
carbonaceous shale layer indicate lack oxygenic sedimentary condition, and
was suboxic/anoxic conditions during the transgressive phase. The hydrothermal
fluids from the open ocean affected the whole deposition process of
the black rock series.