Coral lumps in Early Kimmeridgian oyster shellbeds and oolites of Małogoszcz
Journal Title: Volumina Jurassica - Year 2005, Vol 3, Issue 1
Abstract
Scleractinian corals occurring scarcely in the Lower Kimmeridgian [i]Actinostreon [/i](=[i]Lopha[/i], =[i]Alectryonia[/i]) shellbeds at Malogoszcz in the Holy Cross Mountains, Central Poland, are represented by abraded colonies densely riddled by rock-boring bivalves ([i]Lithophaga [/i]inclusa Phillips, [i]Gastrochaena [/i]sp.) and polychaetes ([i]Potamilla [/i]sp.). The taxonomically recognised specimens include [i]Complexastrea[/i] [i]burgundiae [/i](de Blainville, 1830), [i]Dimorphocoenia [/i]sp., [i]Ovalastrea caryophylloides [/i](Goldfuss, 1826), and [i]Thamnasteria [/i]graeilis (Miinster, 1826). AlI colonies are preserved in the form of hollows, the wall s of which bear moulds of coral calyces, and of bivalve and polychaete borings. Taking into account the structural features of shellbeds and their faunistic content (uprooted crinoids [i]Apiocrinites[/i], dug-out deeply-infaunal bivalves), stormy agitation is postulated as a basic agent responsible for damaging Actinostreon communities, and their associates. The studied corals are thought to have lived asidethe [i]Actinostreon [/i]gardens, up on a muddy bottom, from where they have been stirred-up during the storm cataclysm, having been then abraded and riddled by rock-borers repeatedly until laid down in a shellbed and transferred in to the fossil record. The extremely shallow-water conditions, under which the ostreid [i]Actinostreon [/i]has lived, suggest the typically opportunistic nature or the associated corals, the same as of[i] Ovalastrea caryophylloides [/i](Goldfuss, 1826) from oolitic shoals, and the only colony of which completes the coral assemblage of Malogoszcz. The opportunism or ali these corals differs them from the habit of hermatypie forms from coeval and Oxfordian patch-reef communities of the Holy Cross Mountains ([i]cf.[/i] Roniewicz & Roniewicz 1968, 1971).
Authors and Affiliations
Andrzej RADWAŃSKI, Ewa RONIEWICZ
Keywords
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