Abstract

The Upper Kutei Basin lies at the intersection of two major tectonic trends. These are oriented approximately NW-SE (Adang-Cross Barito Trend) and NNE-SSW (Meratus Trend). Interpretation of Radar Imagery and field structural data demonstrates that these two trends are characterized by two distinct joint classes. The NNE-SSW Meratus trend is reflected by the dominant megalinear orientation and also in the distribution of deep magnetic anomalies which divide the Upper Kutei area into two distinct magnetic domains.

The distribution of deep magnetic anomalies is also reflected in the distribution of surface strata. The distribution of surface strata correlate well with interpreted deep seated elements believed to represent a Cretaceous imbricated subduction complex with associated forearc, arc and backarc elements.

Field data and paleogeographic reconstructions imply that the NNW-SSE Meratus trend was an important Paleogene basin precursor.

The NW-SE Adang Cross Barito High trend is interpreted to represent part of a Trans-Kalimantan tectonic zone linking the Pater-noster Platform with the Lupar fault zone. In the Upper Kutei Basin, Lower Paleogene Basins opened northwest parallel to this trend. However, at the end of the Paleogene this basin closed and a permanent southeastward opening Kutei Basin was established.

Tectonic activity on the NW-SE Adang Cross Barito High trend strongly overprinted the NNE-SSW Meratus trend and cuminated in the Late Miocene-Pliocene with major basin inversion and back-thrusting orthogonal to the Adang-Cross Barito trend. The northwest limit of this back thrusting correponds to the interpreted Cretaceous volcanic arc.