| mhorn | Дата: Sunday, 29.07.2012, 10:21 | Сообщение # 1 |
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| Ruban D.A. (2012) Erosional surface at the Middle-Upper Callovian (Middle Jurassic) transition in the Greater Caucasus Basin (northern Neo-Tethys) and tracing its presence in Western Europe, North Africa and Arabia: the influence of regional tectonics // Comunicações Geológicas, Vol. 99, no.1, P.69-76
http://www.lneg.pt/download/5583/ComunGeol_V99_N1_Article%20 (10).pdf
An inter-regional tracing of particular surfaces can help in reconstructions of basin evolution. The available data from the Greater Caucasus Basin, which was a large extending and subsiding basin on the northern margin of the Neo-Tethys Ocean, provide evidence of an erosional surface near the boundary between the E. coronatum and P. athleta ammonite zones, i.e., at the Middle-Upper Callovian transition. Ammonite re-working, hiatuses, and local accumulation of coarse siliciclastics indicate an erosion event across the northern shelfal periphery of this basin. The correlation of Callovian sedimentary sequences of the Greater Caucasus with those of some basins of Western Europe, North Africa, and Arabia suggest only a regional extent of the noted surface. Its analogues are reported from only a few domains such as the North Burgundy Platform. The erosional surface documented in the Greater Caucasus Basin at the Middle-Upper Callovian transition was formed when no global eustatic falls occurred and before the peak of the hypothesized (and yet to be proven) glacial episode. Moreover, the impossibility of inter-regional tracing of the surface precludes any eustatic mechanism for its formation. In fact, it is hard to find many analogues of the erosional surface at the Middle/Upper Callovian boundary in the basins of Western Europe, North Africa, and Arabia. Sediment supply was also not so strong as to shrink sedimentation in the basin. Thus, only regional (=basin-scale) tectonic activity, which altered evolution of both active and "passive" margins of the "Tethyan" oceans in the Jurassic, may explain the formation of this surface. The latter occurs only on the northern margin of the Greater Caucasus Basin, and thus, its origin might have been linked with short-term uplifts on the Scythian Platform. In many other regions of Western Europe, North Africa, and Arabia, the tectonic control on basin evolution also remained important in the Callovian
Middle Jurassic - Lower Cretaceous ammonites & aptychi
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