Naslov
Response of a Carbonate Platform to the Cenomanian–Turonian Drowning and OAE 2: a Case Study from the Adriatic Platform (Dalmatia, Croatia)

Autori
Korbar, Tvrtko ; Glumac, Bosiljka ; Cvetko Tešović, Blanka ; Cadieux, Sarah B.

Izvornik
Journal of sedimentary research (1527-1404) 82 (2012), 3; 163-176

Vrsta, podvrsta i kategorija rada
Radovi u časopisima, članak, znanstveni

Ključne riječi
isolated carbonate platform; Cenomanian–Turonian; OAE 2; synsedimentary tectonics; integrated stratigraphy

Sažetak
Global perturbations during the Cenomanian–Turonian boundary (CTB) interval and the Oceanic Anoxic Event 2 (OAE 2) represent one of the most extensively studied past environmental changes. To explore the response of various carbonate-platform depositional systems to such major environmental perturbations, strata of the intra-Tethyan Adriatic carbonate platform (sensu stricto) from the island of Brač (Adriatic Sea, Croatia) provide excellent exposures and a previously well-established Upper Cretaceous lithostratigraphic framework. Within this context, this study integrated lithostratigraphy, biostratigraphy, and chemostratigraphy to describe a drowned-platform succession underlain and overlain by peritidal carbonates. Carbon-isotope stratigraphy of this succession revealed a shift towards positive δ13C values that reached +4 to +5‰ VPDB, and represent the CTB interval excursion plateau. We observed variations in thickness of the drowned-platform successions and explained them by three superimposed mechanisms: (1) diachronous drowning of platform relief ; (2) intra-platform redeposition of parts of the successions by various mass-gravity transport processes (indicating enhanced instability due to increasing accommodation space related to the late Cenomanian platform drowning and synsedimentary tectonics) ; and (3) migration of major carbonate factories during the recovery of shallow-platform environments. The results indicate that the CTB interval event caused unusual increase in accommodation space on the carbonate platform enabling open-marine influence and synsedimentary redeposition. However, widespread organic-rich black shales reported from coeval strata of other regions have not been documented from the platform-top successions to date, and were probably accumulated in deeper (anoxic) settings below the rising sea level.

Izvorni jezik
Engleski

Znanstvena područja
Geologija

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