engleski

The contact zone between Cenomanian limestones and middle Eocene clastic (tempestite or turbidite?) rocks between Motovun and Karojba (Croatia)

In the area between Karojba and Motovun on the south slope of Šublentica the contact of the carbonate and clastic rock complexes occurs. Some of the outcrops show discordant relationships between the Cenomanian wakestone limestones containing Chondrodonta and the overlying Middle Eocene clastic rocks. The Cretaceous paleo-relief (an outcrop in a abandoned quarry) is covered by a depositional sequence which is characterized by features that could be interpreted either as a) storm (tempestite) BPHF(X)M sequence or b) as a Bouma (Ta-e) turbidite sequence. The first implies conditions in a shallow marine environment below the wave base during calm weather (5-20m), while the second implies a deeper environment with deposition below the wave base during stormy conditions (>x10m). The sequence commences with the deposition of re-deposited foraminifera (nummulites, discocyclina), corals and limestone clasts (B-basal lag or Ta- Bouma interval). This sequence is followed by carbonate sandstones characterized by P-parallel lamination or the Tb- Bouma interval, fine-grained carbonate sandstones and silitites with a hummocky cross stratification or the Tc-Bouma interval, siltites with F-flat lamination or the Td-Bouma interval. The sequence terminates with homogeneous marls (M-mudstone or Te- pelite Bouma interval). However depending on the hypsometric level of the Cretaceous paleo-relief, various intervals of turbiditic sequences are in contact with the Cretaceous beds, including even debrites. Since there are no tempestite sequences developed in the wider region it is probable that the development of these sequences follows the mechanisms of turbidite deposition, therefore deposition in a deep-water environment.

nije evidentirano

nije evidentirano