Aptian parasequence formation as an indicator of relative sea level changes скачать в хорошем качестве

Aptian parasequence formation as an indicator of relative sea level changes

This study covers five Early Cretaceous stratigraphic sections from southern Croatia located on the islands of Korcula, Hvar, Mljet, and the Peljesac Penninsula. The observed succession was deposited on the Adriatic Platform in the Tethys Ocean from 125 ma to 112 ma, resulting in a variable thickness of exposed carbonate rocks from ~30 m to ~77 m. Three depositional facies assemblages are identified within the sections: subtidal, intertidal-supratidal, and subaerial exposure. The subtidal facies are composed of thin to massive bedded bioclastic peloidal lime mudstones to grainstones containing rudist bivalves, benthic forams Palorbitolina lenticularis and Preachrysalidina infractetacea, calcareous alga Salpingoporella dinarica, and microencruster Bacinella irregularis. The intertidal to supratidal facies are thin to thick beds of planar and microbial laminites consisting of alternating layers of lime mudstone and peloidal wacke-packstone. Subaerial exposure facies are thin to thick beds of breccias and residual clay. The vertical succession of these facies shows repeated shallowing-upward parasequence packaging. The hierarchy of facies and lateral distribution of the parasequences indicate that relative sea level changes were the dominant depositional process with minor local progradation of shallow facies. The parasequence architecture indicates an Early Aptian high relative sea level generally coincident with the global Ocean Anoxic Event 1a. The early Late Aptian parasequences show relatively low sea level causing repeated subaerial exposure across the majority of the sections. The limited fossil record, periods of erosion, and amalgamation of parasequences in subtidal facies all inhibit high resolution correlation of the observed sea level changes to global events.