Mark Rudolph

B. Sc. Honours Thesis

Seismic Stratigraphy of the Exmouth Plateau

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The Barrow Group deltaic sediments of the Exmouth Plateau were mapped with forty seismic lines and data from five wells. The mapping shows two deltaic sequences which are separated by a flooding surface. The source areas at the southern margin near Australia have been eroded but still show between 500 and 2000 m of relief.

Uplift occurred in three areas. One area of uplift occurred close to the continent of Australia. This area was a junction of an extension zone, south of the Exmouth Plateau, and the Cape Range Fracture Zone. The uplift created an area of sediment supply. The second area of uplift occurred on the Cape Range Fracture Zone southwest of the plateau which resulted from motion on the transform fault. This motion created topographic highs for sediment sources and basin lows along the zone of transpression and transtension. Continuing transform fault motion caused the high areas to subside while basinal areas experienced uplift. The third area of uplift appeared at the diverging plateau margin. The origin of this source resulted from volcanic activity along the uplifted margin.

Seismic mapping of the Barrow Group generated isopach and structural contour maps of two sequences. The maps show sequence distribution and depositional surface topography. The lower sequence prograded as a 300 m high delta front to the northwest from both source areas simultaneously. Sediment coverage of the area is 120 km x 150 km. An isopach map of the younger delta shows it also prograded north from both source areas simultaneously on a 200 m high delta front to cover an area 180 km x 150 km.

Well data from five sites in the area show close correlation of the sequence boundaries on seismic profiles to dinoflagellate an age for the lower sequence of Berriasian and the upper sequence of Valanginian.

Keywords: Exmouth Plateau, Barrow Group, sequence stratigraphy, seismic stratigraphy, tectonic sedimentation, divergent margin, deltaic sedimentation, continental shelf, Australian petroleum, Carnarvon Basin
Pages: 69
Supervisors: Ron Boyd