engleski

Sequence stratigraphy of Eocene incised valley clastics and associated sediments, Island of Rab, Northern Adriatic Sea, Croatia

Clastics of Middle-Late Eocene age were studied on the island of Rab (Northern Adriatic Sea, Croatia) in order to decipher their depositional history, depositional environments, and geometry of sandstone bodies. Detailed outcrop logging and mapping revealed the response of depositional systems to frequent relative sea-level changes, which initiated significant basinward and landward shifts of facies, respectivelly. Tidal sandstones are commonly underlain by shoreface sandstones, and overlain by offshore sandy marls, whereas the latter are again overlain by shoreface sandstones. Major relative sea-level falls initiated basinward shift of faces and the incision of incised valleys or estuaries, and consequently truncated the underlying shelfal sediments. In some cases the accelerated sea-level fall caused rapid shoreface progradation which is interpreted as the forced regression. Relative sea-level rise caused flooding of the incised relief, and deposition of tidal sandstone bodies which overlie Type-I sequence boundaries. The coarse lag sediment of these sequence boundaries locally disappears laterally, and the boundary is granulometrically less prominent. All of the major bounding surfaces have been recognized in the sections studied, although the maximum flooding surface is recognized as a thin zone instead of a single surface. Altogether 28 complete sequences, and 15 parasequences are recognized in the informal unit of the Lopar Sandstones, what documents depositional response to high-frequency relative sea-level oscillations, which were so far unrecognized in Eocene of the eastern Adriatic sea.

Incised valley; paleogeography; sea-level changes; depositional history; sequences;

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