|mhorn||Дата: Monday, 26.08.2013, 10:27 | Сообщение # 1|
|López-Martínez R., Barragán R., Reháková D., Cobiella-Reguera J.L. (2013) Calpionellid distribution and microfacies across the Jurassic/ Cretaceous boundary in western Cuba (Sierra de los Órganos) // Geologica Carpathica, Vol.64, no.3, P.195-208. |
A detailed bed-by-bed sampled stratigraphic section of the Guasasa Formation in the Rancho San Vicente area of the “Sierra de los Órganos”, western Cuba, provides well-supported evidence about facies and calpionellid distribution across the Jurassic/Cretaceous boundary. These new data allowed the definition of an updated and sound calpionellid biozonation scheme for the section. In this scheme, the drowning event of a carbonate platform displayed by the facies of the San Vicente Member, the lowermost unit of the section, is dated as Late Tithonian, Boneti Subzone. The Jurassic/Cretaceous boundary was recognized within the facies of the overlying El Americano Member on the basis of the acme of Calpionella alpina Lorenz. The boundary is placed nearly six meters above the contact between the San Vicente and the El Americano Members, in a facies linked to a sea-level drop. The recorded calpionellid bioevents should allow correlations of the Cuban biozonation scheme herein proposed, with other previously published schemes from distant areas of the Tethyan Domain.
Middle Jurassic - Lower Cretaceous ammonites & aptychi