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The AAPG/Datapages Combined Publications Database

AAPG Bulletin

Abstract


Volume: 74 (1990)

Issue: 8. (August)

First Page: 1183

Last Page: 1202

Title: Seismic Stratigraphy of a Neogene Piggyback Basin, Argentina (1)

Author(s): JAMES A. BEER (2), RICHARD W. ALLMENDINGER (3), DANIEL E. FIGUEROA (4), and TERESA E. JORDAN (3)

Abstract:

Depositional sequences composed of Neogene nonmarine strata are imaged on seismic reflection data from the Iglesia piggyback basin, Argentina. The strata accumulated in an internally drained basin located between the Frontal Cordillera (the High Andes) and the Precordillera thrust belt. Two reflection geometries, onlap and truncation, are observed along four unconformities within the Neogene section. Onlap of reflections onto unconformities defines five distinct intervals of basin growth; local truncation of reflections beneath unconformities defines four intervening intervals of nondeposition or erosion. Along-strike variation in the amount of truncation suggests that erosion was limited to zones through which major streams entered the basin. Postdepositional thrusting o the east side of the basin produced field exposures of the five sequences and allowed examination of the nature of the sequence boundaries.

The Iglesia depositional sequences are interpreted to result from Neogene crustal shortening within the Central Andes. The Iglesia basin has been passively transported above a horizontal decollement that links mid-crustal deformation beneath the Frontal Cordillera with surface thrusting in the Precordillera. Deposition, resulting generally from simultaneous uplift of the Frontal Cordillera and the Precordillera, can be explained by two scenarios: thrust-controlled accumulation where space for deposition was created only during faulting, or drainage-controlled accumulation where deposition occurred only when thrusting cut off through-going drainages linking the Iglesia basin with the foreland.

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