Biogenic structures of unioniform bivalves in wet-interdune deposits (Late Miocene-Early Pliocene, Argentina)
| Autor: | Andreas Wetzel, Noelia Beatriz Carmona, Juan José Ponce |
|---|---|
| Jazyk: | angličtina |
| Rok vydání: | 2018 |
| Předmět: |
0106 biological sciences
010506 paleontology Geochemistry Formation Late Miocene Trace fossil Neogene 01 natural sciences Ciencias de la Tierra y relacionadas con el Medio Ambiente purl.org/becyt/ford/1 [https] purl.org/becyt/ford/1.5 [https] Eolian Dunes Wet-Interdune Geología Ciencias Exactas y Naturales Ecology Evolution Behavior and Systematics Río Negro Formation 0105 earth and related environmental sciences 010604 marine biology & hydrobiology Río Negro Paleontology Sediment Water level Trace Fossil Facies Desiccation Geology CIENCIAS NATURALES Y EXACTAS ichnology |
| Zdroj: | RID-UNRN (UNRN) Universidad Nacional de Río Negro instacron:UNRN CONICET Digital (CONICET) Consejo Nacional de Investigaciones Científicas y Técnicas instacron:CONICET |
| Popis: | Fil: Carmona, Noelia Beatriz. Universidad Nacional de Río Negro. Instituto de Investigación en Paleobiología y Geología. Río Negro; Argentina. Fil: Ponce, Juan José. Universidad Nacional de Río Negro. Instituto de Investigación en Paleobiología y Geología. Río Negro; Argentina. Fil: Wetzel, Andreas. Geologisch–Palaontologisches Institut, Universitat Basel, Bernoullistrasse 32, CH-4056 Basel, Switzerland Environmental changes within a Neogene coastal dune system are recorded by endobenthic unioniform bivalves that lived in muddy or sandy interdune pond sediments. These bivalves were suspension-filter feeders that formed dense, almost monospecific communities in the wet-interdune deposits of the continental intervals of the Río Negro Formation (late Miocene–early Pliocene). Activity of unioniform bivalves appears to be related to sediment type; resting and locomotion traces dominate in the muddy heterolithic facies, whereas equilibrium/escape structures prevail in the sand-dominated heterolithic facies. These traces characterize two scenarios of the wet-interdune development. First, during high and/or relatively stable water levels, bivalves colonized the muddy bottom and produced resting and locomotion traces. When water level dropped due to desiccation, biogenic structures were impacted by the formation of mud cracks and subsequently covered by sand delivered by migrating dunes. Second, in spite of dune migration, some interdune areas remained wet or flooded and, in response to sediment aggradation, the bivalves produced equilibrium or escape structures, depending on the thickness of eolian sand cover. Only the integration of ichnologic and sedimentologic observations allows deciphering the evolution of the Neogene wet-interdune system in such a detail. Environmental changes within a Neogene coastal dune system are recorded by endobenthic unioniform bivalves that lived in muddy or sandy interdune pond sediments. These bivalves were suspension-filter feeders that formed dense, almost monospecific communities in the wet-interdune deposits of the continental intervals of the Río Negro Formation (late Miocene–early Pliocene). Activity of unioniform bivalves appears to be related to sediment type; resting and locomotion traces dominate in the muddy heterolithic facies, whereas equilibrium/escape structures prevail in the sand-dominated heterolithic facies. These traces characterize two scenarios of the wet-interdune development. First, during high and/or relatively stable water levels, bivalves colonized the muddy bottom and produced resting and locomotion traces. When water level dropped due to desiccation, biogenic structures were impacted by the formation of mud cracks and subsequently covered by sand delivered by migrating dunes. Second, in spite of dune migration, some interdune areas remained wet or flooded and, in response to sediment aggradation, the bivalves produced equilibrium or escape structures, depending on the thickness of eolian sand cover. Only the integration of ichnologic and sedimentologic observations allows deciphering the evolution of the Neogene wet-interdune system in such a detail. |
| Databáze: | OpenAIRE |
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