Interpretation: SEG 5 (2):SF149-SF165 (2017)

Authors
Henry Rowe
University of East Anglia
Abstract
A chemostratigraphic study of a 300 m long core recovered from the southeastern central Ordos depocenter reveals thick intervals of fine-grained, organic-rich lacustrine strata, interpreted to represent deepwater deposition under meromictic conditions during lake highstand phases, interspersed with thick intervals of arkosic sandstones, reflective of fluvio-deltaic deposition during lake lowstand phases. Along with elevated concentrations of %Al, traditionally a proxy for clay content, maximum total-organic-carbon values in the deepwater lacustrine facies reach 8%, with average values of approximately 3%. The fine-grained, organic-rich facies is also characterized by elevated S and As concentrations, both proxies for pyrite, an indicator of more stagnant, reducing conditions in the hypolimnion during lake highstand phases. Enrichment factors for redox-sensitive trace elements are not significantly elevated throughout the TOC-rich intervals, but they are punctuated in thinner intervals. Punctuated enrichments in RSTEs reflect episodes of enhanced suboxia/anoxia in the hypolimnion during lake highstand phases resulting from sustained meromixis. Although dramatic shifts between fluvio-deltaic and deepwater lacustrine deposition are recorded in the Yanchang strata, no evidence indicates that the lacustrine system ever built up a significant salt concentration, suggesting that an outlet was maintained throughout much of the depositional history. A chemofacies framework for the Yanchang Formation is developed based on hierarchical cluster analysis and ranking of major element chemostratigraphic results. The outcome of chemofacies analysis is similar to the lithofacies analysis, subdividing the stratigraphic record of calcite-cemented sandstone/siltstone lithologies and silty to finer grained mudstone lithologies based on changes in elemental concentrations that equate to shifts in the relative abundance of mineral contents.
Keywords No keywords specified (fix it)
Categories No categories specified
(categorize this paper)
DOI 10.1190/int-2016-0121.1
Options
Edit this record
Mark as duplicate
Export citation
Find it on Scholar
Request removal from index
Revision history

Download options

PhilArchive copy


Upload a copy of this paper     Check publisher's policy     Papers currently archived: 55,981
External links

Setup an account with your affiliations in order to access resources via your University's proxy server
Configure custom proxy (use this if your affiliation does not provide a proxy)
Through your library

References found in this work BETA

Add more references

Citations of this work BETA

Add more citations

Similar books and articles

Analytics

Added to PP index
2017-10-25

Total views
38 ( #265,469 of 2,403,581 )

Recent downloads (6 months)
5 ( #156,166 of 2,403,581 )

How can I increase my downloads?

Downloads

My notes