Mannum Formation limestone with Gambier Limestone in South Australia. When the sea level fell again in mid-Miocene, the deposited Geera clay and Olney Formation moved westward over the limestone. During Upper Miocene to Pliocene, the sea rose and fell several times. The first sea rise formed the Murravian Gulf and resulted in clay and marl in the west, called the Bookpurnong Formation, with the Calivil Formation river and lake sand in the east. When the sea retreated in Early Pliocene, the Loxton Sands, also informally known as Loxton-Parilla Sands, were formed on the beach on the shore of the emergent land. Locally heavy minerals have been concentrated by wave action, including rutile zircon and ilmenite, forming economic mining opportunities. The Murray River became dammed by uplift of over in the Grampians in Victoria during the Pleistocene about 2.5 Mya. The dam formed Lake Bungunnia, which reached and deposited the Blanchetown Clay therein. Higher rainfall of at least per year kept the lake filled at first, but during later times, rainfall was insufficient, and saline lakes formed, depositing dolomite. Even today, some saline lakes remain as a remnant of the vast lake. The Murray River carved out a new path to the sea via Murray Bridge, replacing its previous exit at Portland, Victoria. The lake was gone by about 0.7 Mya. The Pooraka Formation formed in the north west due to increased erosion, resulting in colluvium depositing. The colluvium forms fans, cones and scree slopes, and often contains clay and breccia. In the flat areas, the Shepparton Formation also resulted from river deposits of floodplain clay. Most of the existing surface dates from Quaternary period. The river deposits from the east have been progressively overlaying the marine deposits further west, as the shore line receded. Within the Pleistocene deposits are three layers of sand that are aquifers, deposited during higher rainfall periods of the interglacials. The floodplain deposits from the current rivers are the Coonambidgal Formation, however this term is used informally for the older Pleistocene flood deposits as well. During the dryer glacial periods the area was arid. References Sedimentary basins of Australia Murray River Geology of New South Wales Geology of Victoria (Australia) Geology of South Australia Landforms of New South Wales Landforms of Victoria (Australia) Landforms of South Australia