--> Platform-to-basin relationships in South Albania: tectono-sedimentary evolution of the Apulian Platform and the Ionian Basin during the Upper Cretaceous

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Platform-to-basin relationships in South Albania: tectono-sedimentary evolution of the Apulian Platform and the Ionian Basin during the Upper Cretaceous

Abstract

Upper Cretaceous and Eocene carbonate reservoirs were discovered in the 60's in southern Albania. They consist of slope and basinal deposits occurring in the Ionian zone. They are composed of hemipelagites, turbidites and slumps. Although many oil fields are already in production, the tectono-sedimentary evolution of this system is still poorly understood. Therefore, investigations have been made aiming to unravel several key points referring to the sediment-source, facies types and evolutionary stages of sedimentation of this Tethian carbonate system.

Being part of the peri-Adriatic domain, the Apulian platform and the Ionian Basin are presently integrated in a fold-and-thrust belt extending along a NW-SE direction. The succession was studied in eight outcrops situated along three distinctive thrust fronts. Sedimentological investigations led to the determination of two facies classifications regarding platform and basinal / gravity-related deposits. Geologic timeframe was defined using two techniques: i) Biostratigraphical analysis was perform on the platform deposits as well as the basinal / slope deposits, using benthic and pelagic foraminifera determination respectively ii) Strontium Isotope Stratigraphy was carried out on both platform and basinal / slope deposits.

The western part of the basin reveals a strong influence of the Apulian margin, alternatively shedding sediment basinward, by means of a tectonically controlled edge. Several sedimentation stages are identified: i) The Late Albian to Cenomanian period is characterized by meter-scale lagoonal parasequences on the platform. Few muddy debrites inserted in hemipelagites settle along the margin while carbonate mud is widely spread throughout the basin. A general subsidence of the platform / basin system is attested during this period, with no significant influx of the platform basinward; ii) from the Turonian to the Santonian, a significant sedimentation change is documented on the platform, from shoal dominated to subtidal dominated depositional settings. The latter is attested by the abrupt settling of rudistdominated sequences. Hemipelagites are uniformly deposited in the basin, associated with phosphorites; iii) the end of Santonian reveals an important calciclastic influx derived from the rudist-dominated platform. Gravity-flow deposits document coarsening and thickening upward sequences showing a progressive increase in sediment shedding during the Campanian; iv) the Late Campanian-Early Maastrichtian period reflects a major change in sedimentation processes. Syn-sedimentary deformations are attested with reworking of thick sediment packages on both platform and basin / slope system. The latter can be traced along the Apulian margin and document an eastwards downslope movement, testifying of instabilities along the edge of Apulia during this period. (Go to www.searchanddiscovery.com to view figures.)