CIG   05423
CENTRO DE INVESTIGACIONES GEOLOGICAS
Unidad Ejecutora - UE
artículos
Título:
Graptolites and trilobites from the Eusebio Ayala Formation (Hirnantian to early Llandovery), Paraná Basin, Eastern Paraguay.
Autor/es:
ALFARO, MARTA BEATRIZ; URIZ, NORBERTO JAVIER; CINGOLANI, CARLOS ALBERTO; TORTELLO, FRANCO; BIDONE, ANDREA ROSA; GALEANO INCHAUSTI, JULIO CÉSAR
Revista:
GEOLOGICAL JOURNAL (CHICHESTER)
Editorial:
JOHN WILEY & SONS LTD
Referencias:
Lugar: Londres; Año: 2012 vol. 48 p. 236 - 247
ISSN:
0072-1050
Resumen:
A low-diversity graptolite fauna from the upper part of the Eusebio Ayala Formation exposed in the intracratonic Paraná Basin of eastern Paraguay is reported herein. The sections studied are composed dominantly of red micaceous mudstones with intercalations of purple sandstones from a series of clay quarries (Santa Elena; Galeano; Western Itauguá) around Itauguá city. The graptolites Metaclimacograptus sp., Normalograptus Metaclimacograptus sp., Normalograptus  cf. ajjeri (Legrand), and Normalograptus cf. medius (Törnquist) indicate an early Llandovery age for the upper Eusebio Ayala unit. Compared  to coeval, postglacial successions in southwestern Gondwana, the graptolites studied have their closest affinities with those from the Rhuddanian  lower Lipeón (Subandean Ranges, northwestern Argentina) and La Chilca (Precordillera) formations. In addition, a trilobite assemblage dominated by the genus Mucronaspis was collected from the Eusebio Ayala Formation type locality near Eusebio Ayala city. The latter represents  an isolated small outcrop which seems to be latest Ordovician (Hirnantian) in age.