LATERAL THICKENING OF SEDIMENTARY UNITS: SEDIMENT COMPACTION VS. TECTONICS

Abstract

When a new sedimentary unit is deposited over a region with significant differences in the thickness of the pre-existing sedimentary cover, the thickness of the new unit may express lateral differences in sediment compaction and not in the intensity of the tectonic-driven subsidence. This effect is examined here and quantified as a function of the thickness of the pre-exiting section. It is shown that when the thickness of the pre-existing section varies from nearly zero to a few kilometers, this effect may easily dominate the tectonic-driven subsidence. When the pre-existing section is thicker than 5 km over the entire region, this effect decreases significantly; and when the sedimentary cover is more than 10 km thick over the entire basin, this effect has no real influence on the trend of lateral thickening. Another related effect discussed here is the reburial of uplifted regions in light of the assumption that reburied sediments do not compact anymore until they reach their previous maximal depth. This emphasizes the need to consider the amount of uplift in backstripping in order to understand the later tectonics.