Leaves in turbidite sands: The main source of oil and gas in the deep-water Kutei Basin, Indonesia: Discussion

Abstract

Saller et al. (2006) have concluded that leaves in the upper Miocene turbidite sands were the main source of oil and gas in the deep-water Kutei Basin, East Kalimantan (Borneo), Indonesia. They have reported that oils from the Kutei Basin have high (4–7) pristane/phytane ratios, suggesting a coaly organic source. This is consistent with other observations made on oils from the Gippsland Basin in Australia, showing high pristane/phytane ratios (5–6) that were attributed to coniferous rain forests and related land-plant organic matter (Shanmugam, 1985). Saller et al. (2006) have also concluded that leaf fragments were carried into deep water along with sand by turbidity currents during lowstands of sea level. This conclusion deserves close scientific scrutiny. Although Saller et al. (2006) have discussed both geochemical and sedimentological aspects, I confine this discussion to sedimentological details. I also take this opportunity to introduce more clarity into our understanding of deep-water deposition through discussing conceptual, observational, and interpretational problems. First, Saller et al. (2006, p. 1588) stated that “Specific well names and depths are not included in this manuscript for confidentiality reasons.” The strength of any scientific article is its transparency of data, which provides other researchers an opportunity to verify the conclusions of an article without constraints. Saller et al. used cuttings samples from 50 wells and conventional core samples from 16 wells, but because they did not provide a map showing well locations, it is impossible to evaluate the relative position of a sample with respect to the paleoshelf edge. This is critical to the central theme of this article, which is the source of land-plant organic matter (i.e., highstand delta versus lowstand shelf-edge delta). Saller et al. could have included a location map of wells, but could have changed the original well names. Second, the basic tenet of …