Bioerosion Patterns in Cretaceous-Cenozoic Benthic Foraminiferal Tests from Patagonia and Tierra Del Fuego Island, Argentina
Published:January 01, 2007
N. Malumián, M.I. López Cabrera, C. Náñez, E.B. Olivero, 2007. "Bioerosion Patterns in Cretaceous-Cenozoic Benthic Foraminiferal Tests from Patagonia and Tierra Del Fuego Island, Argentina", Sediment–Organism Interactions: A Multifaceted Ichnology, Richard G. Bromley, Luis A. Buatois, Gabriela Mángano, Jorge F. Genise, Ricardo N. Melchor
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Cretaceous-Cenozoic benthic foraminiferal assemblages from Patagonia and Tierra del Fuego are characteristic mainly of shallow settings of the cool-temperate Austral geobioprovince, lacking larger foraminifera. A survey of more than 2000 samples, including illustrations in systematic papers, shows that bioeroded tests are uncommon. However, a general pattern is indicated by (a) an apparent chronological distribution of boring abundance and diversity: during the early Cretaceous-Campanian, borings are very rare, and in the Maastrichtian-Paleocene, rare. In the Middle Eocene an increased abundance of borings and boring types is apparent, including: circular, subcircular, roughly or neatly beveled; multiple, concentrated in juvenile chambers or one per chamber; and associated with main or supplementary apertures. (b) Taxa selectivity: predator preferences are evident mainly among the most common species, in genera either of Antarctic origin (e.g., Ammoelphidiella) or abundant in cool-temperate waters (e.g., Buccella), and in elongate thin-walled genera (e.g., Bulimina, Buliminella, Praebulimina). (c) Site selectivity: this is evident in a non-random distribution of borings observed in several cases. Scarcity or absence of bioerosion in the Early Cretaceous may be related to widespread dysaerobic-anaerobic conditions, that could diminish predation pressure and/or the dominance of finely perforate thick-walled Nodosariacea. Increased bioerosion in the Middle Eocene, coincident with a temperature fall during the Cenozoic long cooling trend, affects genera that previously were recorded as intensely bored from the Antarctic Pliocene, giving a polar aspect to many Fuegian foraminiferal assemblages.
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Sediment–Organism Interactions: A Multifaceted Ichnology
The field of Ichnology bridges the gap between the areas of paleontology and sedimentology, but has connections to many subdisciplines within these areas. Biogenic structures record the behavior of their tracemakers and provide valuable information in paleoecologic and paleoenvironmental analysis. As in situ ethologic structures, trace fossils or ichnofossils yield valuable insights into the paleoecology of ancient benthic communities and the environmental dynamics of depositional systems. Ichnology is truly a multifaceted field, and a broad selection of its facets is represented in the 28 papers of this volume. The papers are the product of Ichnia 2004, the First International Congress on Ichnology, convened by Jorge F. Genise and held from 19 to 23 April 2004 at the Museo Paleontológico Egidio Feruglio in Trelew, Patagonia, Argentina. Seven papers connected with the congress, containing ichnotaxonomy, were published separately, in Ichnos, volume 13, issue 4. Several symposium volumes, books, and short-course notes have been published in recent years and ichnology can be considered a particularly active research area in steady growth. The 28 papers herein are arranged in five groups that reveal the broad scope of ichnology.