INVESTIGADORES
BRESSAN Graciela Susana
congresos y reuniones científicas
Título:
Taphonomy of crinoid beds associated with large subaqueous dunes from the Lower Cretaceous of the Neuquén basin, west-central Argentina
Autor/es:
LAZO, DARÍO G.; BRESSAN, GRACIELA SUSANA; SCHWARZ, ERNESTO; VEIGA, GONZALO D.
Lugar:
Ankara
Reunión:
Simposio; 9th International Symposium of the Cretaceous System; 2013
Institución organizadora:
Middle East Technical University
Resumen:
Exceptionally preserved stalked crinoids
have been recorded from Valanginian beds of the Agrio Formation in the Neuquén Basin. The crinoid beds occurred within
a 30-m thick succession consisting of cross-bedded sandstones and mixed
sediments. Cross-bedded sets are up to 5 m thick and the crinoid beds are invariably
associated with reactivation surfaces separating consecutive sets. The scale
and architecture of the cross-bedded strata suggest that they represent the
migration of large subaqueous dunes (or sand waves) in a tide-influenced
subtidal setting. Crinoids appear as well preserved specimens with different degrees
of articulation and as disarticulated remains. The best preserved specimens
were recorded from the base of a key crinoid bed. Some of these specimens are
almost completely articulated including stem with cirri, calyx and arms with
pinnules, whereas other specimens are represented either by articulated arms
with attached pinnules or isolated stem fragments with cirri. Completely (o
quitar el completely directamente y dejar Articulated como inicio de frase) articulated
crinoids indicate that these specimens were suddenly buried, probably during
life, and no subsequent reworking or bioturbation took place. Avalanching was
the most likely burial mechanism of stalked crinoids that probably inhabited
the dune toe and/or through on the leeward side of the bedforms. In contrast, beds
with disarticulated specimens suggest that these suffered significant exposure
time prior to final burial in the dune through.