期刊
JOURNAL OF THE GEOLOGICAL SOCIETY
卷 172, 期 3, 页码 349-356出版社
GEOLOGICAL SOC PUBL HOUSE
DOI: 10.1144/jgs2014-071
关键词
-
资金
- Deutsche Forschungsgemeinschaft [KR 2095/7-1]
- Deutsche Forschungsgemeinschaft (DFG) [LE 867/8-1, LE 867/8-2, SPP 1006]
- Swedish Scientific Drilling Program (SSDP)
- Danish Research Council for Independent Research \ Natural Sciences
- VILLUM Foundation
- Villum Fonden [00007376] Funding Source: researchfish
The limestones of the upper Katian Boda mud mounds (Ordovician) of the Siljan district in central Sweden are deeply fractured. The fissures were partly synsedimentary and are often lined with stromatolite-like crusts. These crusts thus far are the only known subaerial Ordovician speleothems. They reach depths of up to 30 m below the former mound top. Macroscopically the crusts form decimetre-sized, cone-shaped domal aggregates, stalactites and stalagmites. Microfabric and morphology identify them as microbially mediated speleothems in a dark environment. Combined Sr and C isotope values indicate a formation of the speleothems from meteoric waters without influence of a significant soil horizon. For the first time the age of the speleothems can be precisely constrained by delta C-13 whole-rock and brachiopod shell isotope data to the mid-Hirnantian. Repeated and/or prolonged subaerial exposure of the Boda mud mounds during the Hirnantian is evident from karst surfaces and early cements in the mound capping carbonates. The speleothems and the karst surfaces record an estimated sea-level fall in the range of 80-130 m within the time window of the Hirnantian Isotopic Carbon Excursion. This massive regression coincides with maximum ice sheet extent inferred from sections in West Gondwana.
作者
我是这篇论文的作者
点击您的名字以认领此论文并将其添加到您的个人资料中。
推荐
暂无数据