Preservation of large titanousaur sauropods in overbank fluvial facies: a case study in the Cretaceous of Argentina.

GONZÁLEZ RIGA, B.J.; ASTINI R.A.,

JOURNAL OF SOUTH AMERICAN EARTH SCIENCES

Elsevier

Lugar: Amsterdam; Año: 2007 vol. 23 p. 290 - 303

0895-9811

Patagonia exhibits a particularly abundant record of Cretaceous dinosaurs with worldwide relevance. Although paleontological studies are relatively numerous, few include taphonomic information about these faunas. This contribution provides the first detailed sedimentological and taphonomical analyses of a dinosaur bone quarry from northern Neuque´n Basin. At Arroyo Seco (Mendoza Province, Argentina), a large parautochthonous/autochthonous accumulation of articulated and disarticulated bones that represent several sauropod individuals has been discovered. The fossil remains, assigned to Mendozasaurus neguyelap Gonza´lez Riga, correspond to a large (18? 27-m long) sauropod titanosaur collected in the strata of the Rý´o Neuque´n Subgroup (late Turoronian?late Coniacian). A taphonomic viewpoint recognizes a two-fold division into biostratinomic and fossil-diagenetic processes. Biostratinomic processes include (1) subaerial biodegradation of sauropod carcasses on well-drained floodplains, (2) partial or total skeletal disarticulation, (3) reorientation of bones by sporadic overbank flows, and (4) subaerial weathering. Fossil-diagenetic processes include (1) plastic deformation of bones, (2) initial permineralization with hematite, (3) fracturing and brittle deformation due to lithostatic pressure; (4) secondary permineralization with calcite in vascular canals and fractures, and (5) postfossilization bone weathering. This type of bone concentration, also present in Rinco´n de los Sauces (northern Patagonia), suggests that overbank facies tended to accumulate large titanosaur bones. This taphonomic mode, referred to as ??overbank bone assemblages??, outlines the potential of crevasse splay facies as important sources of paleontological data in Cretaceous meandering fluvial systems.Mendozasaurus neguyelap Gonza´lez Riga, correspond to a large (18? 27-m long) sauropod titanosaur collected in the strata of the Rý´o Neuque´n Subgroup (late Turoronian?late Coniacian). A taphonomic viewpoint recognizes a two-fold division into biostratinomic and fossil-diagenetic processes. Biostratinomic processes include (1) subaerial biodegradation of sauropod carcasses on well-drained floodplains, (2) partial or total skeletal disarticulation, (3) reorientation of bones by sporadic overbank flows, and (4) subaerial weathering. Fossil-diagenetic processes include (1) plastic deformation of bones, (2) initial permineralization with hematite, (3) fracturing and brittle deformation due to lithostatic pressure; (4) secondary permineralization with calcite in vascular canals and fractures, and (5) postfossilization bone weathering. This type of bone concentration, also present in Rinco´n de los Sauces (northern Patagonia), suggests that overbank facies tended to accumulate large titanosaur bones. This taphonomic mode, referred to as ??overbank bone assemblages??, outlines the potential of crevasse splay facies as important sources of paleontological data in Cretaceous meandering fluvial systems.