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Elisabeth L. Jorissen*, A. de Leeuw, Christiaan G.C. van Baak, Oleg Mandic, Marius Stoica, Hemmo A. Abels, Wout Krijgsman
Research output: Contribution to journal › Article › Academic › peer-review
Sedimentological facies models for (semi-)isolated basins are less well developed than those for marine environments, but are critical for our understanding of both present-day and ancient deltaic sediment records in restricted depositional environments. This study considers an 835 m thick sedimentary succession of mid-Pliocene age, which accumulated in the Dacian Basin, a former embayment of the Black Sea. Detailed sedimentological and palaeontological analyses reveal a regression from distal prodelta deposits with brackish water faunas to delta-top deposits with freshwater faunas. Sediments contain frequent hyperpycnal plumes and an enrichment in terrestrial organic material, ichnofossils and in situ brackish and freshwater faunas. Deltaic progradation created thin, sharply-based sand bodies formed by multiple terminal distributary channels, covering a wide depositional area. The system experienced frequent delta-lobe switching, resulting in numerous thin parasequences. Parasequences are overlain by erosive reddish oxidized sand beds, enriched in broken, abraded brackish and freshwater shells. These beds were formed after sediment starvation, on top of abandoned delta lobes during each flooding event. A robust magnetostratigraphic time frame allowed for comparison between the observed sedimentary cyclicity and the amplitude and frequency of astronomical forcing cycles. Our results indicate that parasequence frequencies are significantly higher than the number of time equivalent astronomical cycles. This suggests that delta-lobe switching was due to autogenic processes. We consider the observed facies architecture typical for a delta prograding on a low-gradient slope into a shallow, brackish, protected, semi-isolated basin. Furthermore, in the absence of significant wave and tidal influence, sediment progradation in such a protected depositional setting shaped a delta, strongly river-dominated.
Original language | English |
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Pages (from-to) | 1-23 |
Journal | Sedimentary Geology |
Volume | 368 |
DOIs | |
Publication status | Published - Jun 2018 |
This research was supported by the project PRIDE (Pontocaspian RIse and DEmise), which has received funding from the European Union's Horizon 2020 research and innovation program, under the Marie Sklodowska-Curie [grant agreement No 642973]. Part of this research was conducted during a secondment at CASP, one of the partner institutes of PRIDE, which we thank for its cooperation and hospitality. Finally, we thank the reviewers and Jasper Knight, editor of Sedimentary Geology, for their constructive comments of the manuscript.
Research output: Contribution to conference › Abstract › Academic