Separata de:

GONzALEZ BONORINO G.

et a11999. Geologia del Noroeste Argentino, I, 91-126. Salta

Estratigrafia y correlaci6n regional:

BIOESTRATIGRAFIA DE LA FORMACION PUNCOVISCANA YUNIDADES EQUIVALENTES EN EL NOA * Florencio G. AceFiolaza1, Guillermo F AceFiolaza 1, Susana Esteban I

Biostratigraphy of the Puncoviscana Formation and equivalents units in northwestemArgentina. Historically, rocks assigned to the Puncoviscana Formation (s.l.) were referred as Precambrian in age. The reason for this age determination was that it did not exist paleontological records in the unit, and that they were overlied by a clear unconformity separating all of them from fossiliferous Cambrian and Ordovician strata. In the early 70's the first ichnological records appeared in the Puncoviscana Formation, resulting on the temporal reasignation of the whole unit, and an increasing interest on this "unfossiliferous" sequence. Several new localities in Jujuy, Salta, Tucuman and La Rioja were added to this first ichnofossiliferous record in the Sierra de la Ovejeria (Catamarca province). Nowadays, close to twenty localities are known and a varied ichnofauna is recorded, dating the sequence within the Vendian - Tommolian transition. Among the known traces are: Asaphoidichnus, Cochlichnus, Didymaulichnus, Dimorphichnus, Diplichnites, Glockeria, Gordia, Helminthoida, Helminthopsis, Mon01nolphichnus, Mullipodichnus, Neonereites, Nereites, Oldhamia, Phycodes, Planolites, Protichnites, Protopaleodictyon, Protovirgularia, Scolicia, Squamodictyon, Tasmanadia, Torrowangea, Tiernavia, and some soft body fauna assigned to Beltanelliformis, Sekwia and Igen et isp. indet A and B. Based on the ichnological record of the strata, levels assigned to the Vendian crop out in Tucuman Province; while the outcrops of the other provinces could be assigned to the Tommotian-earliest Cambrian, due to the recurrent record of arthropod traces . The intracratonic, marginal and autochtonous setting for the Puncoviscana basin within Precambrian-Cambrian times is emphatized. The basin would have developed with the expansive type of the proto-andean margin, vinculated to a thinner area on the crust.

INSUGEO, (CONICET-UNT), Miguel Lillo 205 AOOO San Miguel de Tucuman E-mail: [email protected] 0 [email protected]

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ArtIculo en recordaci6n y homenaje al Dr. Felipe Ram6n Durand (1948-1998), colega y amigo, quien fuera un infatigable estudioso de la problematica dellfmite. Precambrico/Cambrico del noroeste argentino

Introducci6n

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