Late Silurian palynomorphs from the Los Espejos Formation, Precordillera of San Juan, Argentina: diversity, palaeoenvironmental and palaeogeographic significance

RUBINSTEIN, CLAUDIA; RUBINSTEIN, CLAUDIA; GARCIA MURO, VICTORIA; GARCIA MURO, VICTORIA; STEEMANS, PHILIPPE; STEEMANS, PHILIPPE

ACTA PALAEONTOLOGICA POLONICA

INST PALEOBIOLOGII PAN

Año: 2018 vol. 63 p. 41 - 61

0567-7920

Thepalynological content from the Cerro La Chilca and Quebrada Ancha sections ofthe Wenlock? to Přídolí Los Espejos Formation, in the Argentinean Precordillerais studied. The marine palynomorphs exhibit higher relative abundance and diversityin almost all the productive samples, except for the uppermost ones from bothsections, in coincidence with the shift towards more proximal facies in thispart. The Los Espejos Formation yielded a total of 114 species of marine organicwalled-phytoplankton, 52 species of miospores and two non-marine phytoplanktonspecies. The lower part of the Los Espejos Formation, dated as Ludfordian,displays the highest phytoplankton diversity and the better-preservedpalynomorphs of the studied samples in both sections. Diversity tends todiminish towards the upper part of the Los Espejos Formation, dated as lateLudfordian?Přídolí, in coincidence with the transition to storm-dominated shelfand shoreface environments and subaerial exposures that probably hinder thepreservation of palynomorphs. Comparisons with coeval phytoplankton assemblagesfrom Gondwana and other palaeoplates such as Laurentia, Baltica, and Avaloniaresult in strong similarities, which suggest a cosmopolitan distributionpattern during the Ludlow and the Přídolí. Conversely, the trilete sporesdisplay more similarities with those from Gondwana and thus suggest a lesserdispersive potential in comparison to phytoplankton. A new trilete sporespecies Emphanisporites? tenuis is described.