Ichnology of Lower Ordovician deposits of Western Gondwana: Analysis of Cruziana groups from Argentina and Europe

MUÑOZ, DIEGO F.

Buenos Aires

Congreso; Humboldt Colloquium "Shaping the Future of German-Argentinian Scientific Cooperation - The Role of Curiosity-Driven Research"; 2018

Alexander von Humboldt Foundation

Ichnology deals with the study of tracesproduced by animals and plants. The analysis of particular ichnofaunas providesvaluable dynamic links with other disciplines as palaeoecology,palaeogeography, biostratigraphy, and others. Cruziana is known since the work of Alcide D´Orbigny in 1842 wherehe published some specimens from Bolivia and included others from France. Then,several papers have been published by other authors dealing with those Cruziana and a ?similar? ichnogenus Rusophycus. The main suspects of havingproduced those traces are trilobites. Ichnospecies of Cruziana and Rusophycusare based on morphological characteristics. First, marks of endopodites showsdifferent claws or setae grouping. Second, the presence of exopodite brushing,genal spines or pleural impressions and cephalo or coxa marks provide valuableinformation about burrowing behavior. Lower Ordovician deposits of the CentralAndean Basin are well known by its rich trace fossils content, particularly Cruziana and Rusophycus. Those ichnogenera have special affinities with otherGondwanan basins such as the Armorican Massif in Europe. The presence of thistype of trace fossils in Gondwana and peripheric terranes allowed Seilacher andothers to establish a biostratigraphic scheme based on the Cruziana and Rusophycusdistribution. From this scheme, two groups are particularly interesting, namelyCruziana semiplicata and Cruziana rugosa, that indicate lateCambrian-lower Tremadocian and Lower to Upper? Ordovician ages respectively. Adeep study of those groups in NW Argentina and the Armorican massif isnecessary in order to understand their possible producers, the relation betweenthe known faunal turnover of the trilobite faunas during the late Tremadocianand their ecologic strategies, the palaeobiogeographic distribution and a moreprecise biostratigraphic distribution.