engleski

Stop 2.1: Eocene incised valley fill clastics of the island of Rab

The Lopar Sandstones are unique in the Eastern Adriatic realm by their silicic composition and shallow-marine origin. The sediment succession documents several episodes of sea level rise and fall, so we can distinguish transgressive and regressive intervals. Sandstones which build sandstone bodies were deposited by traction currents and we interpret them as sandwaves or complex dunes which have been deposited in an outer estuary or incised valley setting. The provenance of sand was outside the present Dinaric range, probably in the Alps. Sandstones that occur as sheet-like bodies, composed of numerous storm beds, are interpreted in terms of a shoreface deposit, that was truncated by the base of sandstone bodies. The shoreface sandstones document facies progradation by gradual increase of thickness of individual beds and reduction in the number of marl interbeds. Where thick sharp-based shoreface sandstones overlie offshore marls, and the contact is marked by thick tempestites, we have interpreted the forced regression. Sandy marls were deposited in a lower shoreface where relicts of storm sandstones are preserved, or offshore where the sand was admixed by a pervasive bioturbation. Succession of offshore- and the overlying shoreface sediments is interpreted as a regressive interval, whereas succession of estuarine sandstones and offshore sediments is interpreted as a transgressive interval. Both are parts of complete depositional sequence(s). Frequent oscillations in sea level forced basinward and landward shifts of facies, so we interpret the depositional environments as a paralic sea and incised valley(s) formed during relative sea-level falls.

clastics, Eocene, Rab, incised valley, sequences

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