Valleys and Channels in the Upper Cretaceous-Lower Tertiary Succession, Northeastern Offshore Canning Basin, Australia

Abstract

During detailed interpretation of seismic survey JNOC88 and some AGSO lines in the northeastern part of the Offshore Canning Basin (Offshore Fitzroy graben and part of the Rowley sub-basin), different scales of valleys and channels in the Albian to Palaeocene succession were noted. The sediments in the area of valley/channel development are dominantly calcilutite, marl, clay, silt, and fine sand deposited in shelf-to-slope water depths. The most evident valleys are associated with the Upper Cretaceous seismic event C6-2 and the Base Tertiary seismic event C13-1, with dominant north-south and northeast trends that are different from the northwest dip of the paleo-slope and -shelf. Small channels developed between C6-2 and C13-1 with an estimated northwest trend. We classify these channels and valleys into four categories: Type 1 to 3 valleys and Type 1 channels according to their scale, morphology, and related geological processes. Among them, Type 1 and Type 2 valleys are associated with the low point of the third-order global sea level curve, whereas the smaller-scale Type 1 channels seem to be associated with flooding surfaces. We suggest that submarine erosion by bottom current, contour current, or slumping formed the Type 1 valley, and similar processes in shallow water formed the Type 2 valley. The Type 3 valley is regarded as a valley cut into a lowstand fan.