OXFORDIAN SILICEOUS SPONGE FACIES FROM THE SOUTHERN MENDOZA, NEUQUEN BASIN, ARGENTINA

BERESI M.S.; KRAUTTER M.

CRICYT- MENDOZA

Simposio; Tercer Simposio Argentino del Jurásico; 2007

Subcomisión del Jurásico C. Arg, de Estratigrafía y Asoc.Geolo. Argentina

OXFORDIAN SILICEOUS SPONGE FACIES FROM THE SOUTHERN MENDOZA, NEUQUEN BASIN, ARGENTINA                                        M.S. Beresi* and M. Krautter** *CRICYT-IANIGLA: A. Ruiz Leal s/n, Parque Gral S. Martín (5500) Mendoza, Argentina. mberesi@lab.cricyt.edu.ar; fax: 54-261-5244201 ** Institut of Geology, Leibniz-University, Callinstr. 30, D-30167 Hannover, Germany. m.krautter@geowi.uni-hannover.de; fax: ++49-511-762 2172  Oxfordian sponge-bearing rocks of the La Manga Formation were deposited in outer shelf to slope settings of a Late Jurassic carbonate complex developed on the foreland side of the Neuquén Basin Argentina, in an embayment open to Pacific circulation. At the Río Potimalal section, southern Mendoza Province, massive buildup facies is made up of hexactinellid sponges contained in a micritic-rich limestone. The fossil association consists of moderately diversified hexactinellid (Hexasterophora, Hexactinosida) sponges (85 %) represented by Laocoetis sp. Cribospongia sp., Ordinatus sp., Linonema calyx and Polygonatium (Hexasterophora, Lyssacinosida, 10%). Demospongiae, primarily "lithistids" form only 5 % of the association. Most specimens belong to Cribrospongiidae and Laocoetidae. Sponges are usually bodily preserved and exhibit calcified spicules. Other benthic fauna consists of pelecypods, bryozoans and echinoids. Siliceous sponges inhabited a mud dominated environment in quiet water settings with low energy, including a very low sedimentation rate, soft substrates and sufficient nutrients in the water column. Andean Oxfordian facies with sponge-bearing mudstones of the Neuquén basin have been interpreted as deposits of a transgressive to highstand systems tract. Such an interpretation was also given in case of European sponge facies widely developed in the Upper Jurassic basins of the Tethyan realm.  Asistencia  con  presentación de Poster. *CRICYT-IANIGLA: A. Ruiz Leal s/n, Parque Gral S. Martín (5500) Mendoza, Argentina. mberesi@lab.cricyt.edu.ar; fax: 54-261-5244201 ** Institut of Geology, Leibniz-University, Callinstr. 30, D-30167 Hannover, Germany. m.krautter@geowi.uni-hannover.de; fax: ++49-511-762 2172  Oxfordian sponge-bearing rocks of the La Manga Formation were deposited in outer shelf to slope settings of a Late Jurassic carbonate complex developed on the foreland side of the Neuquén Basin Argentina, in an embayment open to Pacific circulation. At the Río Potimalal section, southern Mendoza Province, massive buildup facies is made up of hexactinellid sponges contained in a micritic-rich limestone. The fossil association consists of moderately diversified hexactinellid (Hexasterophora, Hexactinosida) sponges (85 %) represented by Laocoetis sp. Cribospongia sp., Ordinatus sp., Linonema calyx and Polygonatium (Hexasterophora, Lyssacinosida, 10%). Demospongiae, primarily "lithistids" form only 5 % of the association. Most specimens belong to Cribrospongiidae and Laocoetidae. Sponges are usually bodily preserved and exhibit calcified spicules. Other benthic fauna consists of pelecypods, bryozoans and echinoids. Siliceous sponges inhabited a mud dominated environment in quiet water settings with low energy, including a very low sedimentation rate, soft substrates and sufficient nutrients in the water column. Andean Oxfordian facies with sponge-bearing mudstones of the Neuquén basin have been interpreted as deposits of a transgressive to highstand systems tract. Such an interpretation was also given in case of European sponge facies widely developed in the Upper Jurassic basins of the Tethyan realm.  Asistencia  con  presentación de Poster.