Ichnologic evidence of a Cambrian age in the southern Amazon Craton: Implications for the onset of the Western Gondwana history

• Published in: Journal of South American earth sciences Vol. 76; pp. 482 - 488
• Main Authors: Santos, Hudson P., Mángano, M. Gabriela, Soares, Joelson L., Nogueira, Afonso C.R., Bandeira, José, Rudnitzki, Isaac D.
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01-07-2017
• ISSN: 0895-9811; 1873-0647
• DOI: 10.1016/j.jsames.2017.03.008

Colonization of the infaunal ecospace by burrowing bilaterians is one of the most important behavioral innovations during the Ediacaran-Cambrian transition. The establishment of vertical burrows by suspension feeders in high-energy nearshore settings during Cambrian Age 2 is reflected by the appearance of the Skolithos Ichnofacies. For the first time, unquestionable vertical burrows typical of the Skolithos Ichnofacies, such as Skolithos linearis, Diplocraterion parallelum and Arenicolites isp., are recorded from nearshore siliciclastic deposits of the Raizama Formation, southeastern Amazon Craton, Brazil. Integration of ichnologic and sedimentologic datasets suggests that these trace fossils record colonization of high-energy and well-oxygenated nearshore sandy environments. Chronostratigraphically, the presence of these vertical burrows indicates an age not older than early Cambrian for the Raizama Formation, which traditionally has been regarded as Ediacaran. Therefore, the Raizama ichnofauna illustrates the advent of modern Phanerozoic ecology marked by the Agronomic Revolution. The discovery of the Skolithos Ichnofacies in these shallow-marine strata suggests possible connections between some central Western Gondwana basins.
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•Nearshore siliciclastic deposits of southeastern Amazon Craton, Brazil, illustrates the advent of the Agronomic Revolution.•For the first time, unquestionable vertical burrows typical of the Skolithos Ichnofacies are recorded in Raizama Formation.•Trace fossil-bearing deposits of the Raizama Formation are regarded as Cambrian Age 2 or younger.•Cambrian trace fossils in the northern Paraguay Belt yield insights into the ecology and paleogeography of Western Gondwana.