Estratigrafía, sedimentología y palinología de la Formación Sloggett (Paleogeno continental), Tierra del Fuego.

E. B. OLIVERO; V. BARREDA; S. A. MARENSSI; S. N. SANTILLANA; D. R. MARTINIONI

Revista de la Asociación Geológica Argentina

Asociación Geológica Argentina

Lugar: Buenos Aires; Año: 1998 vol. 53 p. 504 - 516

0004-4822

STRATIGRAPHY, SEDIMENTOLOGY, AND PALYNOLOY OF THE SLOGGETT FORMATION (CONTINENTAL PALEOGENE), TIERRA DEL FUEGO, ARGENTINA.   -   ABSTRACT:   At Bahía Sloggett, the Punta Cactus Formation (yellowish and reddish fanglomerate and conglomerate, 125 m) and the Sloggett Formation (95 m) are exposed in a small tectonic window below a thrust block of the Lemaire Formation (Jurassic). The Sloggett Formation presents a complex arrangement of lenticular beds consisting of two members and four facies associations (FA). The basal dark gray Gris Member (40 m) consists of massive carbonaceous mudstone (FA 4) cut by conglomerate and pebbly sandstone channels (FA 2). In abrupt contact, the overlying yellowish Bayo Member (55 m) is a major complex of lenticular conglomerate and sandstone (FA 1) grading laterally and vertically to heterolithic mudstone and coal measures, containing large trees (FA 3), and channeled conglomerate (FA 2). Facies and palynology suggest a fluvial system with humid and vegetated areas. The Gris Member is interpreted as floodplain deposits (FA 4) cut by small channels (FA 2). The abrupt superposition of FA 1 (Bayo Member) suggests avulsion of the main channel system; FA 3 and FA 2 are interpreted as overbank deposits. The clastic composition of both the Punta Cactus and Sloggett formations is remarkably uniform, consisting exclusively of acidic volcanic detritus derived from the Lemaire Formation. Both units are interpreted as part of the same fluvial basin with a point source in the thrust block of the Lemaire Formation, grading from proximal deposits of an alluvial fan (Punta Cactus Formation) to a distal braided/anastomosed channel complex and associated floodplain deposits (Sloggett Formation). The recorded beech, podocarp, and protacean pollen, fern and fungal spores, and fresh-water algae from the Sloggett Formation, together with the absence of typical Oligocene-Neogene palynomorphs, suggests most probably a late Eocene age.