Volcanic ash as a potential cause of mass kills of Cenozoic decapod crustaceans in Argentina

FELDMANN, R.; MAGUIRE, E.; CASADÍO, S.; SCHWEITZER, C.

Mendoza

Congreso; 4th International Palaeontological Congress; 2014

Cricyt

Literature documenting the effects of modern volcanic ash falls on terrestrial plants and animals is voluminous; however the impact of ash falls on extant marine organisms is extremely limited. Work known to us refers primarily to recovery assemblages of marine microorganisms rather than describing the fate of benthic communities. Because Andean volcanic activity has had a profound effect of marine and non-marine sedimentary deposits at least since the Cretaceous Period, Argentina is an ideal candidate as an area for defining criteria to test whether ash falls indeed do severely affect benthic organisms. A recent study by us on the decapod fauna of the early Miocene Monte León Formation in Santa Cruz Province provided strong evidence for a mass kill resulting from volcanic emanations. The decapods collected were representatives of Chaceon peruvianus, all of whom were fully articulated corpses oriented in a similar direction and all with their anterior regions elevated. The third maxillipeds, the outermost mouthparts, were opened wide and extended outward from the normal, relaxed position. This posture has been interpreted as resulting from suffocation in living crabs, and has been interpreted as suffocation of a large number of Chaceon peruvianus by volcanic ash in the Monte León Formation. Stratigraphically above the layer with crabs, the sediments contained less volcanic material and indicated subsequent successional recovery of the normal benthic community. Present study of the Puerto Madryn Formation exposed on Peninsula Valdés, Chubut Province, and anticipated studies in other Patagonian localities, will test the ubiquity of the effect of volcanic ash falls on benthic marine organisms. Field work for the early studies was supported by NSF EF-0531670 to RMF and CES. Current research supported by the Graduate Student Senate, Kent State University to EM CONYCET to SC.