engleski

Proposal for a regional chronostratigraphical stage-division of the Middle Pleistocene in SE Europe, based on glacigenic sediments in the Croatian Dinarides.

Quaternary sediments have been studied for the past 20 years in the area of the Croatian Dinarides, specifically the northeast Adriatic coast and islands, the Velebit Mt. and northern Dalmatia. The sedimentological research yielded a glacigenic and periglacial origin of the studied sediments, which are attributed to several glacial and interglacial stages in the Croatian Dinarides. Glacial sediments are diamicts (tills or tillites) interpreted as ground, medial and lateral moraines. Clasts with glacial striae, ice-shaped (faceted, bullet-shape and conical) and ice-shattered clasts are the main evidence of their glacial origin. The ground moraines are identified as Rujno, Paklenica and Novigrad Members. The Paklenica Mb., found also on Krk and Rab Islands, documents the furthest seawards extent of glaciation. Another characteristic landform of ice-marginal zone are kame-terraces which are well-preserved on the Krk and Pag Islands built of stratified slopeward dipping supraglacial debris and glaciofluvial sediments. Glacifluvial sediments comprise both glacial outwash deposits of braided streams and flood plains, and fluvial deposits of meandering rivers, represented by sand and gravel deposits. Their glacigenic origin is based on facies association, since they occur with tills or tillites, and contain glacially derived boulders and blocks, sometimes also lithologically exotic debris. The proglacial glacifluvial sediments are found on Krk and Pag Islands (kame-terraces) and are widespread in Northern Dalmatia. Glacilacustrine sediments comprise a) clay-silt sediments with complex clastic varves, and b) varve-like calcisiltites with drop-stones, being the main diagnostic feature for their proglacial character. Varved sediments with abundant plant macrofossils, ostracods and small bivalves are found at Ždrilo coast. The fossil macroflora indicates transition to cold stage and ice-advance documented by the Paklenica Mb. moraines. Varved-like sediments with dropstones are exposed at Novigrad Sea and Seline coastal sections. Subglacial hydro-fractures, ice-contact subglacial sedimentary features and ice-wedge casts at the Novigrad Sea coastal section document the most southwards glacial extent and periglacial palaeoenvironment. Glacideltaic sediments are an alternation of conglomerates, calcarenites and calcisiltites. Significant characteristics for glacial attribution are ice-striated clasts in conglomerates, and their association with glacilacustrine sediments, all exposed along the Seline coast and named Starigrad Unit. The sediment succession documents a subglacial deltaic environment of the ice terminal zone. The sedimentary record revealed three phases of extensive glacial advance and retreat during the Middle Pleistocene. Seven allo-morpho-litho-stratigraphic members were defined within the studied sedimentary successions. Three are represented by glacial deposits: the Starigrad Mb. as the oldest but with no ages available yet, the Paklenica Mb. as the most extensive one and older than 350 ka, and Novigrad Mb. older than 145.4 ± 6.2 ka (both dates are calibrated U-series ages of calcite cements in a moraine. Their characteristics correspond to glacial sediments in Montenegro and Greece, so the preliminary use of Pindus Mt. chronostratigraphy is the most suitable. Thereafter, the Paklenica Mb.that correlates well with the Ninkovići Mb. in Montenegro is ascribed to the Skamnellian Stage, and the Novigrad Mb. appends to the Vlasian Stage. The Seline Mb., Nozret Mb. and Karin Mb. are represented by lacustrine systems, whereas the Paljuv Mb. is represented by fluvial systems. Despite of only a few U-series minimum ages, we propose a partial regional stage-division by naming three cold stages: Starigradian Stage as tentative equivalent to one of the Cromerian glacials of Western Europe (MIS 14 or 16), Paklenician Stage as time-equivalent of the Skamnellian Stage (MIS 12) and Novigradian Stage as time-equivalent of the Vlasian Stage (MIS 6) in Greece. Further dating of sediments is crucial to complete the proposed regional division.

Pleistocene stratigraphy; nomenclature; stages; glaciation

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