Seismic study of the Magallanes fold-and-thrust belt, southern Argentinean continental margein: Preliminary results

TASSONE A.; LODOLO E.; LIPPAI, H,; COMINGUEZ, A.; FOSTER, M.; GELETTI, R.; MENICHETTI, M.

Montevideo, Uruguay

Congreso; X Congreso Latinoamericano de Geología; 2001

Asociación Geológica de Uruguay

Within the framework of the TESAC Project (Tectonic Evolution of the South America-Scotia plate boundary during the Cenozoic), about 900 km of multichannel seismic reflection profiles were acquired off the Atlantic coast of the Tierra del Fuego Island. The profiles cut across the South America-Scotia plate boundary, a transform margin which traverses in an E-W direction the Island. The geophysical survey was carried out by the Argentinean vessel A.R.A. Puerto Deseado on October 1999. The acquisition system installed on the ship consisted of a 1200 m long, 96 channels, marine streamer and an array of two Gl-guns. Data processing and interpretation of one segment of a seismic reflection profile is presented in this contribution. The pre-stack data processing included: (1) the re-format; (2) re-sampling; (3) amplitude recovery; (4) data sorting; (5) spike deconvolution on CDP gathers; (6) semblance velocity analyses; (7) normal move-out correction; (8) mute; (9) stack; (10) three traces mixing; (11) time variant filter and trace equalization. The post-stack processing involved the time migration of the seismic section, using the FOCUS seismic package. The processed and interpreted seismic line (which trends roughly NW-SE), shows a complex superposition of different tectonic structures, with presence of extensional, compressional and transtensional features in the area located to the north of Isla de los Estados. The profile, which crosses the offshore part of the Magallanes fold-and-thrust belt, images the deep structural framework of part of this tectonic province. The iden­tification of acoustic fabrics and seismic discontinuities allowed us to recognize four main units. Overlaying the acoustic basement (Seismic unit 1), there is by another unit (Seismic unit 2) which displays tabular geometry and some reflector packages of high amplitude; this unit might be related to the volcanic and volcaniclastic sequences of TobiTera/Lemaire Fms. The Seismic Unit 3 displays an irregular shape and internal reflector configurations of moderate amplitude and continuity and low- to moderate