Do coastal fronts influence bioerosion patterns along Patagonia? Late Quaternary ichnological tools from Golfo San Jorge

RICHIANO, SEBASTIÁN; AGUIRRE, MARINA; CASTELLANOS, IGNACIO; DAVIES, KAREN; FARINATI, ESTER

JOURNAL OF MARINE SYSTEMS

ELSEVIER SCIENCE BV

Año: 2017

0924-7963

Late Quaternary marine molluscan skeletal concentrations from Argentina constitute a remarkable record ofvariations in palaeoceanographical conditions during interglacial times (mainly ca. 125 ka to present).Particularly, the Golfo San Jorge coastal area represents an extraordinary geographical zone to target fromdifferent points of view, mainly due to its linkage between northern and southern Patagonia, characterized byparticular and contrasting physico-chemical conditions with direct consequences for littoral marine communities,determining their composition and structure. Among varied biological activities controlled by differentenvironmental factors (i.e., substrate nature, sedimentation rates, water depth, sea surface temperature, salinity,nutrients-productivity), bioerosion traces can provide palaeoenvironmental evidence with important implicationsfor palaeoclimate interpretations. In addition, the application of bioerosion patterns regionally and throughtime is a recent valuable worthy palaeoenvironmental tool not as yet developed for Patagonia. We attempted tocharacterize, qualitatively/semiquantitatively, the ichnotaxonomic composition of the coastal area of northernGolfo San Jorge since the Late Pleistocene; to compare results with those obtained for other geographical areasalong Patagonia and the Bonaerensian coastal sectors; lastly, to evaluate its palaeoenvironmental/palaeoclimaticsignificance in a clue area in terms of circulation patterns near the Southern Ocean climatic pump. AtBustamante (Northern Patagonia Frontal System) Domichnia traces were dominant during the Late Pleistocenewhile Praedichnia in the mid-Holocene. Bustamante exhibits the highest ichnodiversity for the wholeArgentinean coastal area. Ichnodiversity is not strongly different between Late Pleistocene and mid-Holoceneinterglacials and compared to present; however, the relative abundance of some ichnotaxa (e.g., Oichnus,Iramena, Pennatichnus, at Camarones; Oichnus, Iramena, Pinaceocladichnus, at Bustamante) differs across time.These variations, particularly the highest abundance in the Late Pleistocene (mainly Last Interglacial) of tracesmade by bryozoans- associated at present with modern enhanced productivity levels and coastal fronts in theArgentine continental shelf- point to higher productivity and more intensified northern Patagonia Front, as aresult of a different palaeocirculation pattern, reinforcing previous independent sources of evidence based onmolluscan palaeobiogeographical analyses.