engleski

Ditrupa-Nummulitic facies in the Eocene shallow carbonate, Tatra Mts (Poland) – Palaeoecological implications and taphonomy

The shallow- water carbonates of the so called “Nummulitic Eocene” of the Tatra Mts, Poland, is a transgressive sequence which starts with conglomerates composed of bedrock Mesozoic clasts. The conglomerates are covered by Lower Bartonian detrital dolomites (extraclastic packstones) with rare larger benthic foraminifera mainly Nummulites sp. In the upper part of this succession Numulite-Ditrupa and Nummulites bank facies occur.These deposits are followed by the upper Bartonian Discocyclina-bearing facies comprising Nummulite-Discocyclina bioclastic packstone and Discocyclina rudstone, which are ffinally overlain by the Priabonian glauconitic marls with planktonic foraminifera. The uppermost part of the section is characterized by distinct facies variation and is represented by organodetritic limestones, flora beds limestones and upper conglomerates. These deposits are of the Priabonian age. The carbonates are succeeded by thick complex of Oligocene turbiditic deposits. The studied Nummulite-Ditrupa wackestone ( up to 2.0 m thick) is composed predominantly of sannd-size dolomite grains, quartz, calcareous tubes of serpulid polychaete Ditrupa sp., numerous robust and spherical tests of Nummulites perforatus and bivalve shells. The tests of foraminifera bear evidence of fragmentation, abrasion as well as borings. They display current imbrication or linear accumulation. Some tests are encrusted by Miniacina or Haddonia type foraminifera, and show geopetal infillings. Occasionally, nummulitd test’s poles are truncated or the outer surface of the youngest whorl is exfoliated. The Nummulite-Ditrupa facies constitutes a transition between littoral detritic dolomites and Nummulitic bank facies composed exclusively of Nummulites perforatus. The proposed transitional facies contains relatively well-preserved Nummulites with taphonomically modified tests (taphonomic category 1 sensu Beavington Penney, 2004)suggesting seawards transport over a short distance by the action of storm-driven currents and sediment gravity flows. Abundant Ditrupa in well-sorted in fine- and medium-grained sands support their dependence upon substrate and most probably energy regime. The abundance of Ditrupa tubes (suspension - feeders) points to an increasing input of organic flux to the sea bottom.

Tatra Mts; Eocene; Ditrupa; Nummulites; Taphonomy

Rad je bio predstavljen kao poster na kongresu o tafonomiji i fosilizaciji, 7th International Meeting on Taphonomy and Fossilization, Taphos 2014 koji je održan u Ferrari od 10.-13.09.2014.