Taphonomic analysis of fossil concentrations from La manga Formation (Oxfordian), neuquén Basin, Mendoza province, Argentina.

BRESSAN, G.S.; PALMA, R.M

JOURNAL OF IBERIAN GEOLOGY

SERVICIO PUBLICACIONES

Lugar: Madrid; Año: 2010 vol. 36 p. 55 - 72

1698-6180

AbstractGriphaeid-dominated fossil concentrations ofLa Manga Formation are characterized on the basis oftaphonomic, sedimentologic, stratigraphic and palaeoecologic criteria. These concentrations are present in the basal deposits (Unit 1) of three outcrops in the locality ofBardas Blancas. Their attributes allow distinguishing seven different fossil accumulations: A) Channelized fossil concentrations of Gtyphaea sp.; B) Shell beds of Glyphaea sp. highly reworked; C) Shell beds of Gryphaea sp. l110derately reworked; D) Accumulations of Glyphaea sp. with biomicrite to biopelmicrite matrix; E) Shell detritus; F) Accumulations produced by bottom currents; and G) Accumulations found in clumps. Accumulations A-C were deposited by high energy processes (storm waves and currents) in the upper middle ramp. Accumulations D and E were produced by high energy processes (storm waves and currents) but the final depositions were produced out of suspension in low energy environments, in Jower middle ramp settings. Accumulations F were generated by weak ballom currents, meanwhile accumulations G correspond to gryphaeíds associations reworked by bioturbators 01´ by hydraulic processes aíler variable periods of pennanence in sediment/water interface. Both are interpreted as lower middle 01´ outer ramp. This interpretation suggests that these deposits that in previous works were interpreted as outer ramp settings, characterize middle and outer ramp settings. The vertical distribution of fossil concentrations frol11 upper middle ramp to