Cyclic anoxic events in the Early Cretaceous Tethys Ocean

Cyclic black shale and nannofossil limestone units of the Lower Cretaceous Maiolica Formation of the southern Alps have been studied. From sedimentological data, the black shale units appear to have been formed in an euxinic basin that experienced periodic overturn and basinal aeration. The carbon-1...

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Bibliographic Details
Published in:Geology (Boulder) 1979-01, Vol.7 (3), p.147-151
Main Authors: Weissert, H, McKenzie, J, Hochuli, P
Format: Article
Language:English
Subjects:
algae
Alps
anaerobic environment
Barremian
black shale
C-13/C-12
carbon
carbonate rocks
clastic rocks
Cretaceous
cyclic processes
depositional environment
Europe
isotopes
Italy
limestone
Lower Cretaceous
Maiolica Limestone
Marine
Mesozoic
microfossils
nannofossils
O-18/O-16
oxygen
paleo-oceanography
paleoclimatology
palynomorphs
Plantae
ratios
sedimentary rocks
sedimentation
Southern Europe
stable isotopes
stratigraphy
Tethys
thallophytes
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Summary:Cyclic black shale and nannofossil limestone units of the Lower Cretaceous Maiolica Formation of the southern Alps have been studied. From sedimentological data, the black shale units appear to have been formed in an euxinic basin that experienced periodic overturn and basinal aeration. The carbon-13 values of the calcareous nannofossils serve as indicators of paleocirculation. In the Barremian, the palynological spectra of the black shale units reveal a drastic alteration from a warm, dry to a cooler, humid climate. As a result, thermohaline circulation in the western Tethys Ocean was replaced by density stratification, and stagnation of the deeper basins followed.
ISSN:0091-7613
1943-2682
DOI:10.1130/0091-7613(1979)7<147:CAEITE>2.0.CO;2