The lower fine-grained interval of the Alfarcito Member of the Upper Cambrian-Tremadocian …

• Abstract
• Introduction
• Stratigraphic framework
• Systematic ichnology
• Discussion
• References
• Figures

Biology Articles » Paleobiology » Paleoichnology » Ichnology of the Alfarcito Member (Santa Rosita Formation) of northwestern Argentina: animal-substrate interactions in a lower Paleozoic wave-dominated shallow sea » Introduction

Introduction

- Ichnology of the Alfarcito Member (Santa Rosita Formation) of northwestern Argentina: animal-substrate interactions in a lower Paleozoic wave-dominated shallow sea

Invertebrate ichnofossils are abundant in lower Paleozoic deposits of northwestern Argentina. In particular, Cambrian-Ordovician ichnofaunas have been the focus of a series of studies during the 1970s and early 1980s ( e.g . Aceñolaza, 1978; Aceñolaza and Durand, 1978; Aceñolaza and Fernández, 1978, 1984; Aceñolaza and Manca, 1982; Fernández and Lisiak, 1984). These essentially dealt with ichnofossil identification and ichnofacies recognition. However, in recent years there have been several attempts to refine previous ichnotaxonomic assessments, record new forms and track the sedimentologic and stratigraphic distribution of trace fossils in order to explore paleoecological, paleoenvironmental, sequence stratigraphic, biostratigraphic and evolutionary aspects of these ichnofaunas (for review see Mángano and Buatois, 2003). The Alfarcito Member is, therefore, appropriate for the multidimensional approach to ichnology advocated by the authors in previous studies ( e.g . Mángano et al ., 2002a).
Extensive outcrops of the Upper Cambrian-Tremadocian Santa Rosita Formation are exposed in the Cordillera Oriental of northwestern Argentina (figure 1). This unit records a complex depositional history, encompassing a wide range of sedimentary environments, such as fluvial, tide-dominated estuarine, and wave-dominated shallow marine (Mángano and Buatois, 2002; Buatois and Mángano, 2003). In particular, the lower interval of the Alfarcito Member, which is the focus of this study, represents an overall transgressive-regressive cycle, recording the establishment of an open-marine, shallow, low-gradient platform, affected by fairweather and storm waves. Trace fossils are common in outcrops in the Quebrada de Humahuaca area (figure 1). The integration of ichnologic data within a sedimentologic and sequence stratigraphic framework allows us to evaluate in detail the significance of the Alfarcito ichnofauna. Additionally, we provide systematic descriptions and critically re-evaluate the taxonomic status of each of the ichnotaxa previously described.