Salterella in the Argentine Precordillera: an Early Cambrian palaeobiogeographic indicator of Laurentian affinity

Abstract

This paper documents Salterella maccullochi (Murchison) in the Precordillera of western Argentina in the present-day southern hemisphere. The record of these Early Cambrian small conical-shaped fossils, assigned to the extinct phylum Agmata, provides further palaeobiogeographic evidence to consider the Argentine Precordillera an exotic terrane to Gondwana that originally rifted from Laurentia. For palaeogeographic reconstructions, Salterella can be considered as an organism equally important and biogeographically as meaningful as the olenellid trilobites due to their limited dispersal and demonstrated link to Laurentian shallow-water inner-shelf facies. It has not been found anywhere in Gondwana. Salterella existed for only a very short interval of time, but spread almost instantaneously around Laurentia. On this basis, the Early Cambrian of the Precordillera terrane remains the more conclusive palaeobiogeographical link to Laurentia. Salterella provides another line of evidence supporting palaeontological, sedimentologic, stratigraphic, palaeomagnetic, and isotopic evidence for a Laurentia origin of the Precordillera terrane.