Xiphosurid trackways in a Lower Cretaceous tidal flat in Patagonia: Palaeoecological implications and the involvement of microbial mats in trace-fossil preservation.

FERNANDEZ D.E,; PAZOS, P.J.

PALAEOGEOGRAPHY PALAEOCLIMATOLOGY PALAEOECOLOGY

ELSEVIER SCIENCE BV

Lugar: Amsterdam; Año: 2013 vol. 375 p. 16 - 29

0031-0182

Lower Cretaceous trackways assignable to xiphosurids were recently found in tidaly influenced marginal-marine deposits of the Agrio Formation (Patagonia Argentina). The aim of this paper is to describe these trace fossils in detail, discuss their conditions of preservation, make paleoecological and taphonomic inferences from them, and analyse the importance of their paleogeographic location. These trace fossils are assigned to Kouphichnium, and five track morphotypes are established. Microbially induced sedimentary structures (MISS) are associated with the trackways. Scanning electron microscope (SEM) studies document the involvement of microbial mats in the preservation by the presence of cyanobacteria-like filament sheaths. The studied surface could represent a high-tide mating ground associated with a very shallow water deposits on a warm Cretaceous tidal flat. This is the first convincingly documented trackways produced by xiphosurids in the Early Cretaceous worldwide and the second fossil record of this group form the Cretaceous in the South Hemisphere.