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Marine derived 87Sr/86Sr in coal, a new key to geochronology and palaeoenvironment: Elucidation of the India-Eurasia and China-Indochina collisions in Yunnan, China

Spiro, Baruch F.; Liu, Jingjing; Dai, Shifeng; Zeng, Rongshu; Large, David; French, David

Authors

Baruch F. Spiro

Jingjing Liu

Shifeng Dai

Rongshu Zeng

DAVID LARGE David.Large@nottingham.ac.uk
Abbott Professor of Geoscience

David French



Abstract

Coal has formed in terrestrial and coastal-marine environments from sub-polar to equatorial regions since the Devonian. It contains detailed long-term records of contemporaneous environment, climate, and subsequent modifications. However, in general, direct chronological information in coal has been sparse. The coal investigated in the present study is from the Mile intermontane basin, Yunnan Province, China, north of an arm of the Mesozoic Tethys Ocean. The coal contains marine geochemical signatures and syngenetic gypsum, common in coastal-marine sediments. The gypsum contains marine-derived Sr and, hence, has geochronological potential. The 87Sr/86Sr record (0.708350-0.708591) in the Mile coal agrees with time-calibrated 87Sr/86Sr records of marine planktonic foraminifera obtained from core DSDP 588C, 22.25-18.27 Ma (Early Miocene). The peat of the Mile coal was deposited over 4.6 Ma., which possibly is the longest deposition of a coal bed in the world to have been found today, although this duration should include the period of non-peat deposition or erosion if present during the time of the 4.6-Ma.

During this period, the regional geological structures were determined by the India-Eurasia collision, which resulted in transform faults with extensive rift structures, including the Mile rhomb-shaped graben. This structural setting enabled the flow of seawater from the South China Sea to reach inland graben structures, including that of the Mile Basin, where peat was deposited. Subsequent deformation caused by the South China-Indochina collision changed the regional structural and geographical-hydrological patterns. This affected the hydrology of the Mile Basin and resulted in its uplift to its present-day elevation of 1350 m.

This study is, to our knowledge, the first to use the marine-derived 87Sr/86Sr indicator and chronometer in coal. At present, marine-influenced peats generated in coastal salt marshes extend from the Arctic Ocean (Alaska and Siberia) in the north, to Patagonia and New Zealand in the south, while mangrove forests abound in equatorial and low-latitude coastal areas. The 87Sr/86Sr record of marine-influenced coal in this study area, provides a key for the determination of age-duration-rate of geological processes in the inland basin, associated with the closure of the Tethys Ocean. Results indicate that this method has potential for providing a temporal framework for geological events and processes in other areas. These may be found near marine shore lines across the globe dating back to the Devonian. Moreover, the 87Sr/86Sr signal in marine-influenced coal can be used for correlation with the well-established 87Sr/86Sr chronology of marine planktonic foraminifera. In turn, the 87Sr/86Sr signal provides a basis for correlating terrestrial records of climate and environment contained in this type of coal and associated sediments, with those of marine sediments, such as those based on δ18O in planktonic foraminifera.

Citation

Spiro, B. F., Liu, J., Dai, S., Zeng, R., Large, D., & French, D. (2019). Marine derived 87Sr/86Sr in coal, a new key to geochronology and palaeoenvironment: Elucidation of the India-Eurasia and China-Indochina collisions in Yunnan, China. International Journal of Coal Geology, 215, https://doi.org/10.1016/j.coal.2019.103304

Journal Article Type Article
Acceptance Date Oct 11, 2019
Online Publication Date Oct 17, 2019
Publication Date Nov 1, 2019
Deposit Date Nov 22, 2019
Publicly Available Date Nov 26, 2019
Journal International Journal of Coal Geology
Print ISSN 0166-5162
Electronic ISSN 1872-7840
Publisher Elsevier
Peer Reviewed Peer Reviewed
Volume 215
Article Number 103304
DOI https://doi.org/10.1016/j.coal.2019.103304
Keywords Coal; Strontium isotopes; Geochronology; Palaeoenvironment; Terrestrial-marine correlation; China-Indochina collision
Public URL https://nottingham-repository.worktribe.com/output/3354902
Publisher URL https://www.sciencedirect.com/science/article/pii/S0166516219307244?via%3Dihub
Additional Information This article is maintained by: Elsevier; Article Title: Marine derived 87Sr/86Sr in coal, a new key to geochronology and palaeoenvironment: Elucidation of the India-Eurasia and China-Indochina collisions in Yunnan, China; Journal Title: International Journal of Coal Geology; CrossRef DOI link to publisher maintained version: https://doi.org/10.1016/j.coal.2019.103304; Content Type: article; Copyright: © 2019 The Authors. Published by Elsevier B.V.

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