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BIOZONATION OF SINEMURIAN AND PLIENSBACHIAN LARGER BENTHIC FORAMINIFERA (VELEBIT MT., CROATIA)

Sinemurian and Pliensbachian shallow-marine carbonates of the Velebit Mt. were deposited on a huge shallow marine carbonate platform covering vast areas of the Southern Tethyan realm, which was very soon, in Toarcian, disintegrated into several smaller platforms (including e.g. Apenninic, Apulian and Adriatic Carbonate Platform) separated by deeper marine basins. Detailed investigation of continuous Sinemurian and Pliensbachian succession outcropping along the Gospić-Karlobag road (Kubus locality – TIŠLJAR et al., 1991), allowed subdivision into 6 biostratigraphic zones, based on distribution and stratigraphic ranges of Lower Jurassic lituolids. Biozone 1: Mesoendothyra sp. lineage zone, Early Sinemurian (= interval zone of SEPTFONTAINE, 1984)- bounded by first appearance of Mesoendothyra sp. and first appearance of Lituosepta recoarensis CATI. Biozone 2) Lituosepta recoarensis lineage zona, Late Sinemurian (SEPTFONTAINE, 1984) – bounded by first appearance of Lituosepta recoarensis CATI and first appearance of Orbitopsella primaeva HENSON. Important taxa: Mesoendothyra sp., Lituosepta recoarensis, Planisepta compressa (HOTTINGER), Amijiella amiji (HENSON), Haurania deserta HENSON, Orbitopsella sp. Biozone 3) Orbitopsella primaeva lineage zona (SEPTFONTAINE, 1984) or Orbitopsella primaeva abundance zone, Early Carixian – bounded by first appearance of Orbitopsella primaeva HENSON and first appearance of Orbitopsella praecursor (GÜMBEL). Important taxa: Mesoendothyra sp., Lituosepta recoarensis, Planisepta compressa, Amijiella amiji, Haurania deserta, Orbitopsella primaeva. Biozone 4) Orbitopsella praecursor taxon-range zone, Late Carixian (SARTONI & CRESCENTI, 1962) - bounded by stratigraphic range of Orbitopsella praecursor (GÜMBEL). Important taxa: Mesoendothyra sp., Paleomayncina termieri (HOTTINGER), Lituosepta recoarensis, Planisepta compressa, Amijiella amiji, Haurania deserta, Orbitopsella primaeva, O. praecursor. Biozone 5: Orbitopsella praecursor– Pseudocyclammina liassica interval zone, Early Domerian – bounded by last appearance of Orbitopsella praecursor (GÜMBEL) and first appearance of Pseudocyclammina liassica HOTTINGER. Important taxa: Mesoendothyra sp., Paleomayncina termieri, Planisepta compressa, Amijiella amiji, Haurania deserta, Agerina martana (FARINACCI). Biozone 6) Pseudocyclammina liassica taxon-range zone, Late Domerian (SEPTFONTAINE, 1984) – corresponding to the stratigraphic range of Pseudocyclammina liassica HOTTINGER. Important taxa include: Mesoendothyra sp., Paleomayncina termieri, Planisepta compressa, Amijiella amiji, Haurania deserta, Agerina martana, Pseudocyclammina liassica. These established biozones correlate very well with contemporaneous deposits of Velebit Mt. (e.g. Mali Halan profile), as well as with other areas of the Karst Dinarides. In the wider Mediterranean realm these results almost completely correspond with biozonation proposed – and correlated with ammonite zones – by SEPTFONTAINE (1984) in the High Atlas Mts. of Morocco. Within the investigated Sinemurian and Pliensbachian shallow-marine inner platform carbonates of the Karst Dinarides, completely lacking ammonites and planktonic foraminifera, determined biozones of larger benthic foraminifera represent the most important tool for stratigraphic correlation.

Benthic Foraminifera; biozonation; Jurassic; Velebit Mt.; Croatia

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