Naslov
Development of transient carbonate ramps in an evolving foreland basin

Autori
Ćosović, Vlasta ; Mrinjek, Ervin ; Nemec, Wojciech ; Španiček, Jelena ; Terzić, Krešimir

Izvornik
Basin research (0950-091X) 30 (2018), 4; 746-765

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

Ključne riječi
Eocene, Dinaric foreland basin, Carbonate ramps, Clastic deposits, Larger benthif foraminifers

Sažetak
This study of an Eocene carbonate succession in the Dinaric Foreland Basin of northern Dalmatia, Croatia, integrates palaeontological and sedimentological data to document a range of successive carbonate ramps formed intermittently during the basin tectonic development. The end-Cretaceous basal erosional unconformity documents the coupling of Adria and Eurasia crustal plates, with a broad antiformal uplift along their suture zone. The overlying late Ypresian carbonate ramp, spanning biozones SBZ 11–12, developed on the retreating forebulge flank of a shallow-marine early synclinal basin. Basal grainstone/packstone facies, dominated by encrusting foraminifers with alveolinids and miliolids, pass upwards into packstones dominated by miliolids and rotaliids with bryozoan and echinoid fragments, indicating an upward bathymetric gradient. Deposition of grainstone facies preceded an end-Ypresian brief subaerial exposure of the basin floor at SBZ 12/13 transition due to post-subductional isostatic uplift. The younger, middle to late Eocene carbonate ramps (SBZ 13–19) formed episodically as perched isolated features on blind-thrust anticlinal ridges in a bathymetrically diversified wedge-top basin, where phases of clastic and skeletal biogenic carbonate sedimentation alternated due to disharmonic thrusting and frequent relative sea-level changes. Clastic sedimentation reflects ridge crest erosion and a forced-regressive progradation of gravelly foreshore and sandy shoreface facies over heterolithic offshore-transition and muddy offshore facies on the ridge flank. Biogenic sedimentation represents inner to middle ramp environments, with the latter passing abruptly into muddy offshore environment. A typical outer ramp environment, known from classic ramp models, was lacking due to bathymetric threshold. Analysis of Larger Benthic Foraminifera (LBF), as biostratigraphic age indicators and palaeobathymetric proxies, aided the distinction and timing of systems tracts. A comparison of local and global sea-level changes allowed the interplay of tectonic and eustatic forcing to be deciphered for the study area.

Izvorni jezik
Engleski

Znanstvena područja
Geologija

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