International Geologiical Congress - Oslo 2008

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HPF-16 Correlation between marine and terrestrial ecosystems

 

Upper Triassic to lowermost Jurassic conchostracan zonation of the Newark Supergroup and its correlation with the marine scale: The CAMP volcanism straddles the Triassic-Jurassic boundary (TJB)

 

Heinz W. Kozur, Geological Consulting (Germany)
Robert E. Weems, U.S. Geological Survey (United States)
 

 

Correlation between the marine and continental Triassic will be one of the most important future research topics in Triassic stratigraphy. Goals of this research are: 1. Subdivision and intercontinental correlation of continental beds. 2. Application of the marine scale to continental deposits by precise correlation between these different facies. 3. Improvement of the numeric scale by cross-correlation between marine and continental beds. Radiometric data from volcanic rocks in marine deposits can be imported to continental lake deposits by detailed biostratigraphic correlation. These imported data can be extended to intervals without primary numerical data by astronomical calibration with Milankovitch cycles that are better recognisable in continental lake deposits than in marine beds. After this, the extended numeric data can be correlated back to the marine realm. For the latest Permian-early Anisian interval, a conchostracan zonation is present (e.g. Kozur & Seidel, 1983; Kozur, 1999) that can be recognised across the entire northern hemisphere and in Gondwana sediments of India and central and eastern Africa. It is closely correlated with the marine scale and as detailed as the ammonoid and conodont zonation in marine sediments. A preliminary conchostracan zonation for the Upper Triassic to basal Jurassic strata of the Newark Supergroup can be closely correlated with conchostracan successions in SW USA, Germanic Basin and partly China and Indochina (Kozur & Weems, 2007). One result is the correlation of the Adamanian lower Lockatong Fm. of Newark Basin with the lower Cumnock Fm. of Deep River Basin, the Lake Ciniza fauna in New Mexico and middle Tuvalian rocks in the Germanic Basin. This age is in agreement with vertebrate results of Lucas and others and with the palynological correlation of Cornet (1977), but in disagreement with the early Norian age for the lower Lockatong Fm. by palaeomagnetic correlation. The former TJB in the Newark Supergroup, indicated by a palynological break, also is marked by a break in the conchostracan fauna, but the beds immediately below this "TJB" belong to the upper (not uppermost) Norian and the beds above (but below the first volcanics of the CAMP) yield Rhaetian conchostracans. The lower Midland Fm., above the first lava flow of the CAMP volcanism, can be correlated with the uppermost Rhaetian lower Pre-Planorbis Beds, and the TJB is about in the middle Midland Fm (FAD of Bulbilimnadia sheni). Thus, the CAMP volcanism straddles the TJB and therefore very probably caused the TJB biotic crisis, as the Siberian Trap and other large-scale volcanism did during the PTB biotic crisis.

 

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