The FROME 1: 250 000 geological sheet is located between latitudes 30° S and 31° S and longitudes 139°30' E and 141° E and covers most of the area between the northern Flinders Ranges and the New South Wales border. Its southern and northern limits approximate to the extremities of Lake Frome, which occupies most of the western portion of the sheet. A southern extension of the Strelecki Desert covers the eastern half of the area. Main access roads are the Barrier Highway, Port Augusta-Wilpena Pound road (which branches off through Oraparinna, thence to Wertaloona) and the Broken Hill-Tibooburra road. A track along the New South Wales side of the border fence gives access to the eastern portion of the sheet, but the fence is about 50 to 100m inside New South Wales, and hence is not shown on the maps. Brougham's Gate is one of the few places where one can pass through the fence into South Australia. Putnamutana Outstation, known locally as "Old Moolawatana", and "Quinyambie", are the only permanent habitations, being located in the northwestern and southeastern corners of the sheet respectively. "Frome Downs" is located immediately south of Lake Frome on CURNAMONA. "Balcanoona" and "Wertaloona" are situated along the foothills of the Flinders Ranges to the west of the sheet, on COPLEY. Part of the pastoral lease of "Wirrealpa" is on FROME sheet area. The climate is dry, hot in summer, with cold winds and occasional frost in winter. Winds are dominantly from the southern quarter with a strong westerly phase during May-August and north winds in summer. Rainfall is low and erratic falling mostly in brief storms with heavier rains of 350-625mm at 10-20 year intervals. Falls occur mainly during February, March, May, June and December, with April being the driest month. The central portion of the map area east of Lake Frome receives the lowest rainfall, while the highest and most reliable occurs near the Flinders Ranges and in the southeastern corner of the sheet. The vegetation is sparse. Plant species most useful for geological mapping are Eucalyptus gillii, which occurs on the Willawortina Formation (Late Cainozoic) dolomitic sediments adjacent to the Flinders Ranges, particularly where calcrete or carbonates are exposed. Callitris columellaris occurs east of Lake Frome and on one island in the lake, tending to prefer the Eurinilla Formation (Quaternary) as a substrate. The nomenclature used for basins follows Wopfner (1972) the term "Frome Embayment" (Ker 1966, Freeman 1966, Wopfner 1966) refers to the Mesozoic sedimentary basin. "Lake Frome Area" refers to the region bounded by the Flinders Ranges to the west, Barrier Ranges to the east and Olary Ranges to the south. The northern limit is taken at an approximate east-west line through the southern portion of Lake Blanche on CALLABONNA. Within the Frome Embayment, the blanketing Cainozoic sediments are unconformable on the Cretaceous and relate to discrete cycle of events, hence the basin of Cainozoic deposition is named the Tarkarooloo Basin (after Lake Tarkarooloo on CURNAMONA). The Poontana Subbasin (after Poontana Ck) occupies the deeper western portion of the Tarkarooloo Basin.