The transition from continental shelf to abyssal plain across a continental slope is of relatively gentle and uniform grade. Canyon incision and erosion into the Neogene section affect the upper slope. In the mid-slope, the section is 3-4s TWT thick and probably forms a southeastern continuation of the Eastern Voluta Trough (Sarma, 1995). Sediment thickness beneath the outer shelf at Prawn 1 is about 3.5s TWT, whereas in a similar setting near Clam 1 there is less than 1s TWT of section above basement.
Faults in the mid-slope Cretaceous section predominantly dip seaward and have low angle listric geometry. In comparison, faults on the upper slope and shelf dip more steeply and switch polarity, signifying reduced extension and a probably strike-slip mechanism.
Two regional cross-sections[PDF_439KB] have been selected to provide examples of the regional geometry, distribution, thickness and structural framework of the Sorell Basin. The two regional cross-sections are:
The Strahan Sub-basin is known to comprise Cretaceous to Recent sediments deposited during the syn-rift and post-rift phases of continental breakup. The Sub-basin is bounded to the north and east by major normal faults, on the hanging wall side of which are basement highs. However, Cape Sorell 1 does not intersect basement and it is not possible to pick basement on seismic data with any confidence on the hanging wall side of the basin-bounding faults through seismic interpretation alone.