Aeronian (Llandovery, Lower Silurian) palynomorphs and graptolites from the Lipeon Formation, Eastern Cordillera, north-west Argentina

The lower levels of the Lipeon Formation, in the Eastern Cordillera, north-west Argentina, yield a marinc-dominated palynomorph assemblage, together with graptolites of mid to late mid Llandovery age (Demirastrites convolutus and probably Stimidograptus sedgivickii zones). The palynomorph assemblage is dominated by acritarchs, but also contains algae and terrestrial cryptospores. Crassiangidina variacornuta, considered a potentially good global biostratigraphical marker for the Upper Llandovery is recovered for the first time from the Silurian of Argentina. The occurrence of this species in strata not Younger than late Aeronian, and independently dated by graptolites, indicates an early first appearance for Crassiangidina variacornuta, in the Lipeon Formation, below the Aeronian/Telychian boundary. The lower part of the unit corresponds to a quiet marine environment; thus supporting that Crassiangidina variacornuta is a facies-sensitive acritarch. (c) 2005 Elsevier SAS. All rights reserved.