Mid-Cretaceous ferns from the Austral Basin, Argentina

IGLESIAS, A.; PASSALIA, M.G.; SANTAMARINA, P.; VARELA, A.; POIRE, D.

General Roca

Congreso; 11° Congreso de la Asociación Paleontológica Argentina; 2016

Asociación Paleontológica Argentina

New mid-Cretaceous fern records from the Piedra Clavada and Mata Amarilla Formations, located at Tres Lagos town, Santa Cruz Province are described. The macrofloristic assemblages throughout all the section show that the angiosperms are the main component of the flora by richness and relative abundance since the earliest Cenomanian. In this contribution we focused on the pteridophyte records that are also quite diverse. They include sterile and fertile leptosporangiate fern fronds and consist of a typical middle Cretaceous fern flora, with elements shared to others coetaneous assemblages of southern Gondwana. At least three taxonomic groups are present throughout the analyzed sections: Matoniaceae, Schizaeaceae and Korallipteris-like fronds (Gleicheniaceae?/Cyatheaceae?/Lophosoriaceae?). However, some relative abundance changes may be related to environmental differences. The middle levels of Piedra Clavada Formation (upper Albian), interpreted as a sandy deltaic environment, are dominated by fertile Matoniaceae accompanied by Equisetaceae in live position. In the uppermost Piedra Clavada section (lowermost Cenomanian) have been identified fertile Dennstaedtiaceae, sterile leaves probably related to Polypodiaceae and several Cladophlebis-like (Osmundaceae?) ferns. In the continental Mata Amarilla Formation (lower Cenomanian), sterile fronds of Schizaeaceae (Anemioideae) are the main fern component. This fact is consistent with the high abundance of cicatricose spores in their palynological assemblages. Extant Schizaeaceae are drought tolerant and grow in warm, sunny habitats and often seasonally dry conditions. The last is in accordance with Mata Amarilla Formation palaeosols, developed under marked seasonal rains and warm conditions.