Statistical appraisal of bed thickness patterns in turbidite successions, Andaman Flysch Group, Andaman Islands, India

Abstract

The bed thickness distribution of two turbidite successions in the Oligocene Andaman Flysch Group, India, which differ in terms of their paleogeography and sediment supply, has been assessed statistically. The purpose was to evaluate depositional cyclicity using the non-parametric Waldron test, and also to assess possible environmental control on the bed thickness–magnitude distribution. Both sections reveal a positively skewed distribution in bed thickness patterns. The Z value obtained through Waldron's test failed to reject the null hypothesis of randomness and thus discards a cyclic pattern. Juxtaposition of sediments of different proximalities in an elongated forearc fan complex is the possible cause for this absence of cyclicity. The studied sections, however, differ in their bed thickness–magnitude distribution. Slope turbidite successions, with sediment supply solely from the outer arc, reveals a scaling behavior while the outer fan succession, with mixing of sediments from different sources, show a negative exponential distribution. This highlights the possible control of the depositional system and sediment supply on the bed thickness–magnitude distribution of turbidite successions irrespective of the triggering mechanism. Unequivocal application of the power law distribution in turbidite successions demands reconsideration.