CIG   05423
CENTRO DE INVESTIGACIONES GEOLOGICAS
Unidad Ejecutora - UE
artículos
Título:
HETEROGENEOUS DISTRIBUTION OF TRACE FOSSILS ACROSS INITIAL TRANSGRESSIVE DEPOSITS IN RIFT BASINS: AN EXAMPLE FROM THE SPRINGHILL FORMATION, AUSTRAL BASIN, PATAGONIA ARGENTINA
Autor/es:
AUGUSTO NICOLÁS VARELA; DANIEL G. POIRÉ; SEBASTIÁN RICHIANO
Revista:
LETHAIA
Editorial:
WILEY-BLACKWELL PUBLISHING, INC
Referencias:
Lugar: Londres; Año: 2016 vol. 49 p. 524 - 539
ISSN:
0024-1164
Resumen:
In the Lago San Martín region (Santa Cruz Province, Argentina), the Springhill Formation (50 to 100 m thick) overlies the syn-rift El Quemado Complex, showing outcrops with wedge-geometry. Four sedimentological logs were obtained from the field and three depositional palaeoenvironments were interpreted. The Springhill Formation starts with fluvial deposits, characterized by channels and floodplains with palaeosol development, passing transitionally to a coastal plain and, finally, to marine sedimentation. The initial sandy transgressive deposits (Facies Association 9) are the main focus of this paper, in which ten ichnogenera (Arenicolites, Bergaueria, Cylindrichnus, Diplocraterion, Macaronichnus, Palaeophycus, Planolites, Ophiomorpha, Rosselia and Skolithos) are described. Two ichnoassociations (foreshore and shoreface) were defined and their distribution was controlled by the local palaeoenvironmental conditions, mainly energy, bathymetry and grain-size of sediments. A highly bioturbated surface (BI= 4) with a limited occurrence that disappears over short distances perpendicularly to the palaeoshoreline was recognized in Section 1. This surface shows a sharp sub-horizontal gently undulating top contact with a bioturbation thickness between 15 and 25cm. This type of surface has limited usefulness as a key correlative surface, because it is spatially restricted in rift basins due to the tectonic activity, which creates high accommodation space rates. A more accurate characterization of the initial transgressive deposits of the Springhill Formation?which is the most important reservoir in southern Patagonia?could provide new ideas to solve problems in subsurface studies.