engleski

Clastuc detritus sources in the Kloštar structure during Late Pannonian and Early Pontian

Kloštar Field is elongated anticline, shallowing toward E. Longitudinal normal fault divides the structure in two parts (NE and SW). This fault had a key crucial role in Upper Pannonian and Lower Pontian reservoirs sedimentation, and spatially it represents border between 2nd (Upper Pannonian) and 1st (Lower Pontian) sandstone series. It is why 1st sandstone series is located only NE from the fault and 2nd just SW. In Upper Pannonian and Lower Pontian the second transtension period lasted in the entire Croatian part of Pannonian Basin. Smaller pull-apart depressions were opened inside particular regional depressions, creating new areas for sedimentation with rate approx. equivalent with tectonic deepening. In Upper Pannonian reservoirs of the 2nd sandstone “series” were deposited, with 3 reservoirs („Alfa“, „Beta“ and „Gama“). After sedimentation of „Gama“ reservoir, mentioned normal fault downlifted NE part of the structure. This area (W from Moslavačka gora Mt.) started to be the deepest part of structure where 11 particular reservoirs had been deposited. In period of Upper Pannonian and Lower Pontian the main material source were the Eastern Alps. Clastics from there had been several times redeposited until reached the Sava Depression. But, obviously, in Late Pannonian and Early Pontian, main depositional centre in the Kloštar structure had been located close to shoreline along Moslavačka gora Mt. It can be very reasonably assumed that part of clastic material had been also eroded from this uplifted basement with local transport probably in short alluvial fans. But, due to sea level rising turbidites were probably only mechanism in Early Pontian, but maybe not in Late Pannonian. It means that we can be assumed source of material on (a) regional + local in Early Pontian and (b) regional in Late Pannonian. The most strong prove would be different mineralogical compositions of cores from these sediments. Unfortunately, there are no available such mineralogical analysis. However, there are studied cores from sandstones and some differences are observed as follows: (a) sandstones from Late Pannonian are more compact, harder ; (b) also are characterised by more mica (small weathering). It means that we can logically assumed additional material source in Pannonian which continuously filled Kloštar structure with clastics, supporting turbidites.

Kloštar structure; Upper Pannonian; Lower Pontian; clastics source; Moslavačka gora Mt.; Eastern Alps

nije evidentirano