engleski

Paleogene NW Adria block surrounded by deeper basins ; study by plankton, small and larger foraminifera on the drowning time in Late Ilerdian, Late Cuisian and Middle Lutetian (N Italy, SW Slovenia, SW Croatia – Istria, Kvarner)

On the NW part of the Paleogene Adriatic Carbonate Platform (PgAd CP), beds from Maastrichtian to late Bartonian were deposited. The sedimentary succession consists of limestone and flysch. Previous investigations confirm the ages from SBZ 1 to SBZ 15 and planktonic zones from P1b-c to E 13. Regarding the Cretaceous paleogeographic basement drowning, three distinct sedimentary belts could be distinguished, delimited by faults or barriers of various origins. The purpose of the present contribution is the temporal definition based on foraminiferal assemblages. In each belt, the youngest assemblage of the shallow-water platform and the oldest assemblage of the deeper-water clastic deposits were determined. On the territory of PgAd CP this is the new attempt at defining the geologic boundaries by the successive appearance of benthic and planktonic foraminiferal groups. The entire Paleogene sedimentary complex lies in the footwall of the Frontal Zone of External Dinaric Thrust belt (Trnovo thrust series), which was related to L. Placer's "Hypothetic fault structure in the Adriatic-Dinaric Mesozoic Carbonate Platform in the continuation of the Budva Trough". After the last rotation of the entire Adria block, at the end of the Miocene and in the latest Pliocene, tectogenetic units formed, arranged from NE towards SW. 1) The Budva Trough with hemipelagic sediments at the Paleocene/Eocene boundary (P 5 - Subbotina velascoensis, Morozovella acuta, M. occlusa) and turbiditic deposits in the basin at the contact with the Dinarides from Goriška brda, Vipava/Pivka basin to Ilirska Bistrica, with numerous nummulites and Alveolina violae ; BiosZ 1. 2) Southwards follows the Kras – Brkini and Vinodol syncline with flora and fauna in lagoonal, shallow marine sediments from the K/T boundary to the Ilerdian/Cuisian passage (SBZ 8, 9). Typical are Alveolina triestina, A. brassica, A. montanarii, (SBZ 10) A. canavarii, A. schwageri. Among planktonic foraminifera appear (P 6/7, E 4/5) Acarinina pseudotopilensis, Morozovella subbotinae ; BiosZ 2. 3) Southward a narrow belt of limestones occurs in Ćićarija Imbricated zone with the same Paleocene and Ilerdian foraminifera, from Rosandra river to Voz peninsula (Island of Krk). Sedimentation continues without interruption from lower to upper Cuisian, extending in middle Cuisan southwards towards Istria. Larger foraminifera (SBZ 12) include the lineage of A. histrica with A. rakoveci, A. cuspidata. Marly and flysch beds of the lower Lutetian are characterized by (P 9/10, E 7/8) A. praetopilensis, A. bullbrooki, and M. aragonensis ; BiosZ 3/1, 2. 4) A parallel zone in the south, the imbricated Adria, is synchronously limited by Istrian dryland, the Adria basin open to east, and the Venetian basin to west. During the middle Cuisian a first transgression covers the land with lagoons, coal seams and bauxite pits. Deposits (SBZ 13, 14) of Alveolina nummulitic limestones follow the lineage of A. levantina, A. elliptica nuttalli, A. frumentiformis, Glomalveolina delicatissima, which pass into the youngest beds on the platform margin to nummulitic, assilina and orthofragmina limestones. They are overlain by Transitional beds and later by flysch, containing (E /10) Turborotalia possagnoensis and Hantkenina dumblei ; BiosZ 4/1, 2, known as the Dalmatian zone. 5) The boreholes of Istra more 5, 4 and 3 are located along the eastern rim of the Venetian basin. The hemipelagic sediments of Middle Eocene contain Morozovelloides crassatus, Acarinina mcgowrani, and in the Upper Eocene Turborotalia cocoaensis ; BiosZ 5. Fauna determined at the transition from the platform to flysch within the NW Paleogene tectogenetic units indicates a separated realm: a shallow carbonate platform with intraplatform barriers in the form of the archipelago extended across Friuli to the Trento platform, on the Lessini shelf, over the Venetian basin.

Paleogene; larger benthic foraminifera; planktonic foraminifera; benthic foraminifera

nije evidentirano