Lithofacial complexes of quaternary deposits in the central and southeastern baltic sea |
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| Authors: | N I Sviridov E M Emelyanov |
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| Institution: | (1) Atlantic Division, Shirshov Institute of Oceanology, Russian Academy of Sciences, pr. Mira 1, 236000 Kaliningrad oblast, Russia |
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| Abstract: | Geological and seismic profiling data (more than 25000 km of seismic profiles and about 1000 sediment sampling stations) collected
during the last 30 yr by research vessels of the Shirshov Institute of Oceanology, Russian Academy of Sciences are summarized.
Seismic records are directly correlated with sediment cores. The distribution map (scale 1 : 500000) of Quaternary lithofacial
complexes corresponding to certain stages of the Baltic Sea evolution is compiled. The following four complexes are distinguished
(from the base to the top): (I) moraine, with maximum thicknesses 60 and 170 m in valleys and ridges respectively: (II) varved
clay of periglacial basins and from the Baltic Ice Lake (BIL), up to 25 m thick in depressions; (III) lacustrinemarine homogeneous
clay with a thickness up to 4–8 m in depressions; (IV) marine sediments (mud, aleurite, coarse-grained deposits) accumulated
in environments with intense bottom currents activity (thickness 2–4 m in the Gotland Basin, 4–6 m in the Gdansk Basin, and
10–20 m in fans and prodeltas). The Quaternary sequence is cut through by inherited valleys, where the thickest Holocene sediments
are noted. Today, these valleys serve as routes of sediment transport to slope bases and central parts of basins. Outblows
of deep gas (through faults and fractures) and diagenetic gas (from sediments) to the bottom surface also occur in the valleys.
Sedimentation rates are higher in the Gdansk Basin (up to 100–120 cm/ka). Thick sand, aleurite, and mud bodies are accumulated
here (about 15–20 m in the Visla River prodelta). The sedimentation rate is slower in the Gotland Basin (up to 50–60 cm/ka),
where thin (2–4 m) sections of more fine-grained mud occur |
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