What was an interglacial river like? Sedimentological investigation of Holsteinian fluvial deposits in eastern Poland

Abstract

Holsteinian flu vial de pos its in the Samica River val ley in east ern Po land have been stud ied, in an ap prox i mately 12 m thick suc ces sion fill ing palaeochannels and com pris ing sandy chan nel fa cies suc ceeded by a pack age of gyttja, peat and silt depos ited in an ox bow lake. Chan nel belts in clud ing palaeochannel fills cut into outwash sands and are over lain by diamictic sands re worked by gelifluction un der periglacial con di tions. Sedimentological and palynological in ves ti ga tions in com bi nation al lowed the rec og ni tion of gla cial and inter gla cial de pos its. The chan nel belt was formed by a typ i cal sand-bed, me ander ing river with de po si tion con trolled by abun dant point bars. The sed i men tary evo lu tion of the Samica val ley is in ter preted in the con text of the gla cial-inter gla cial cy cle. Val ley-scale ero sion and change of river style from braided to me an der ing occurred co evally with the de cay of an ice sheet (deglaciation) and the main phase of me an der ing river sed i men ta tion is at tributed to the lat est Elsterian and early Holsteinian. The next part of the inter gla cial, from pi o neer stage to es tab lished tem per ate con di tions, is re corded in a biogenic ox bow-lake fill. The suc ces sion stud ied has been com pared with pub lished data on the Eu ro pean flu vial de pos its of Mid dle Pleis to cene interglacials. It is pointed out here that river chan nel pat terns in West ern and East ern Eu rope dif fered. Based on this ob ser va tion, some gen eral hy poth e ses re gard ing con ti nen tal-scale clima tic dis tinct ness are put for ward.

Facies and statistical analyses of a crevasse-splay complex at the Tomisławice opencast lignite mine in central Poland

“…Horizontally stratified facies (SCh, Sh) were most likely deposited as a non-channelised sheet flow. At the time, the water flowed over the entire surface of the crevasse splay, thus creating an upper-stage plane bed (Allen, 1982;Bridge, 2003;Boggs, 2012;Zieliński, 2014;Collinson & Mountney, 2019). In general, both these massive and horizontally stratified sediments should be associated with accumulation under subaerial conditions, namely, on the 'dry' surface of a Mid-Miocene mire and not in standing water (Widera et al, 2022).…”

“…The planar cross-stratified facies (Sp, SCp) should be interpreted completely differently. In view of the fact that these facies extend laterally over a length of 200-300 m and the lamination within them is inclined unimodally (towards the N-NNE) at an angle of up to 35°, they represent a former microdelta with typical 'prograding splay deposits' (Mjøs et al, 1993;Bristow et al, 1999;Zieliński, 2014;Chomiak et al, 2019). Therefore, they probably accumulated in shallow lakes or ponds that existed in the area of the Mid-Miocene mires of central Poland (Widera, 2016;Widera et al, 2017aWidera et al, , 2023Widera et al, , 2024Chomiak et al, 2019Chomiak et al, , 2020Wachocki et al, 2020;Dziamara et al, 2022).…”