Bioerosional structures and pseudoborings from Late Jurassic and Late Cretaceous-Paleocene shallow-water carbonates (Northern Calcareous Alps, Austria and SE France) with special reference to cryptobiotic foraminifera |
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Authors: | Felix Schlagintweit |
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Institution: | (1) Lerchenauerstr. 167, 80935 Munich, Germany |
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Abstract: | Examples of bioerosional processes (boring patterns) are described from shallow-water limestones of the Late Jurassic Plassen
Carbonate Platform (PCP) and the Late Cretaceous to Paleocene Gosau Group of the Northern Calcareous Alps, Austria. Some micro-/macro-borings
can be related to distinct ichnotaxa, others are classified in open nomenclature. In the Alpine Late Jurassic, bioerosional
structures recorded from clasts in mass-flows allow palaeogeographical conclusions concerning the source areas. In particular,
these are borings of the Trypanites-ichnofacies detected from clasts (Barmstein limestones) of the PCP or special type of bored ooids of unknown source areas
or restricted autochthonous occurrences. In the Lower Gosau Subgroup, Gastrochaenolites macroborings occur in mobile carbonate clast substrates of shore zone deposits (“Untersberg Marmor”). Different types of
borings are recorded from rudist shells and coral skeleton, some of which are referable to the ichnotaxon Entobia produced by endolithic sponges. In the present study, special attention is paid to the occurrences of the cryptobiotic foraminifera
Troglotella incrustans Wernli and Fookes in the Late Jurassic and Tauchella endolithica Cherchi and Schroeder in the Late Cretaceous. The latter is so far only known to be from the Early Cenomanian of France and
is reported here for the first time from the Late Turonian-Early Coniacian stratigraphic interval where it was found in turbulent
carbonate deposits within borings penetrating bivalve shells or coralline algae. The records of cryptobiotic foraminifera
from the Northern Calcareous Alps are supplemented by a single finding from the Middle Cenomanian of SE France. A palaeoenvironmental
interpretation of the occurrences of the cryptobiotic foraminifera is provided. |
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Keywords: | Bioerosion Borings Pseudoborings Cryptobiotic foraminifera Palaeoenvironment Late Jurassic Plassen Carbonate Platform Late Cretaceous Gosau group Northern Calcareous Alps Austria SE France |
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