Darriwilian graptolites from the Lina range, northwestern Puna of Jujuy, Argentina

ORTEGA, G.; ALBANESI, G. L.; MONALDI, C. R.

Congreso; 11 International Symposium on the Ordovician System; 2011

The Lina range is located in the northwestern Puna of Jujuy Province, at Susques Department, northwestern Argentina. The average altitude at the study area in the Lina range is over 4000 m. At this area extensive outcrops of the Lower Paleozoic are exposed, which are in turn covered by Cenozoic volcanogenic rocks with abundant Pleistocene-Holocene ignimbrites.  Graptolites where firstly discovered in the Lina range by Ramos (1972), who referred the bearer strata to the Upper Ordovician. The author named Lina Formation to a thick succession of shales and graywackes affected by deformation and low grade metamorphism that is exposed in the El Toro village area and to the west, through the road to the Jama pass to Chile. He distinguished a lower sequence cropping out close to the village, where fossil remains were not recorded, and an upper one in the eastern flank of the Lina range. Due to the intense folding affecting these rocks, the real thickness of the formation could not be calculated. The base of the formation is not exposed and at some localities the unit is in tectonic contact with Cenozoic rocks. The graptolite fauna described by Ramos (1972) consist of Glyptograptus euglyphus Lapworth var. linensis n. var. It was recorded from the upper section of the Lina Formation, ca. 17 km west of El Toro, and was correlated tentatively with the Nemagraptus gracilis Zone that globally characterizes the early Sandbian.