Micropaleontología y correlación del Terciario del área carbonífera de Río Turbio, Provincia de Santa Cruz, Argentina

CARRIZO, RAMÓN; MALUMIÁN, NORBERTO; NÁÑEZ, CAROLINA; CARAMÉS, ANDREA; CONCHEYRO, ANDREA

Concepción

Simposio; Simposio sobre el Terciario de Chile; 1990

Departamento de Geociencias, Facultad de Ciencias, Universidad de Concepción

The Tertiary sequence from the Río Turbio area, Santa Cruz Province, is analysed from a micropaleontological and stratigraphical point of view. The study is based on more than 800 subsurface and outhcropping samples. The micropaleontological content is listed for the first time, and the stratigraphical unit are correlated into the Austral Basin. Four main sedimentary cycles are differentiated. The general environment, main foraminiferal and nannoplancton contents , and age assignment of each formation are: 1° cycle. The backshore and shoreface sandstones of the upper section of Cerro Cazador Fm. Bear: Lenticulina turbinate, L. ulatisensis, L. wilcoxensis, L. klagshamnensis, Quadrimorphina allomorphinoides, Nodosaria cf. N. affinis, “Discorbis” mariae, Turborotalia pseudobulloides; Markalius inversus and Hornibrookina sp, (Danian). The shoreface sandstones of Cerro Dorotea Fm.: Elphidium hiltermanni, Kolesnikovella sp., (Upper Paleocene). 2°cycle. The backshore to shoreface glauconitic sandstones of Río Turbio Fm., upper member: Elphidium cf. E. strattoni, Testacarinata inconspicua, Boltovskoyella argentinensis, Discorbinella appossita; Chiasmolithus modestus and Zigrhablithus bijugatus, (Middle Eocene, Lutetian). The Río Turbio Fm. Bears more than 323 millon tn. Of coal, representing one of the most conspicuous events of terminal EWocene in the Austral Basin. 3° cycle. The unconformable overlying fluvial conglomerates of Río Guillermo Fm. (Late Eocene) are followed by unconformable continental pelites and sandstones of Río Leona Fm. (Late Eocene-Early Oligocene). During this cycle, first polar waters invasion occurs in Austral Basin. 4° cycle. The littoral marine sandstones and marsh pelites of Centinela Fm.: Buccella peruviana, f. campsi, Elphidium alvarezianum, Rosalina bahamaensis, Trochammina inflate (Late Oligocene-Early Miocene). They are conformably followed by continental tufaceous pelites and sandstones of Santa Cruz Fm.