In:
Geological Magazine, Cambridge University Press (CUP), Vol. 136, No. 1 ( 1999-01), p. 49-62
Kurzfassung:
An episode of remarkable biotic, climatic, sea-level and facies
changes took place during the late Viruan (Caradoc) epoch in the Baltoscandian area. We studied the
carbon isotopic composition of carbonate sediments from this period. Data on the stable carbon isotopic
composition of whole-rock carbonates from three south Estonian core sections, together
with those on ostracode, distribution are presented. In two core sections, a positive δ 13 C shift of 2 ‰ was revealed in the upper
part of the Keila Stage (mid-Caradoc). The comparison of isotope and ostracode data in the sections
suggested the occurrence of a gap of late Keilan age in the marginal area of the basin equivalent to the
North Estonian Confacies Belt. The beginning of the excursion approximately coincided with climatic
and sea-level changes in the shallow shelf area. The peak of the late Keilan excursion preceded the
biotic crises and maximum black shale accumulation in the Baltoscandian palaeobasin. An approximately
synchronous carbon isotopic event has been reported from North America, referring to a possible
global oceanographic event in the Caradoc epoch. Although the positive carbon isotopic
excursion and related environmental events of the late Keilan age have some unique features, they
show more similarities to the end-Ordovician and Silurian events, characterized by oceanic change
from stratified state to thermohaline circulation state, than to warm anoxic events related to eustatic
sea-level rise.
Materialart:
Online-Ressource
ISSN:
0016-7568
,
1469-5081
DOI:
10.1017/S001675689900223X
Sprache:
Englisch
Verlag:
Cambridge University Press (CUP)
Publikationsdatum:
1999
ZDB Id:
956405-6
ZDB Id:
1479206-0
SSG:
13
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