The MAITLAND Special 1:250,000 scale geological map covers the greater part of South Australia's Yorke Peninsula. The rocks in the map area comprise deformed Palaeoproterozoic and early Mesoproterozoic basement of the south-eastern Gawler Craton, and undeformed Neoproterozoic to Quaternary sediments. More than 90% of the land surface in the map area is covered by Quaternary sand dunes, calcrete, aeolianite and soil. The oldest rocks on Yorke Peninsula belong to the middle Palaeoproterozoic Corny Point Paragneiss (~1920-1845 Ma), which has a Hutchison Group equivalent protolith and was metamorphosed at ~1845 Ma. Several felsic and mafic plutonic suites, principally Gleesons Landing Granite, intrude the paragneiss on the southern part of the peninsula. The early phases of this I-type granite could be as old as ~1855 Ma, and are intruded by megacrystic augen orthogneiss (~1850 Ma). The Gleesons Landing Granite is intruded by the deformed Royston Granite (~1849.5 Ma) and mafic dykes (Tournefort Metadolerite). The late Palaeoproterozoic Wallaroo Group (1770-1740 Ma) comprises a succession of metasediments and volcanics, and in the northern part of the map area hosts the Moonta - Wallaroo Cu-Au deposits. The Wallaroo Group is considered to have been deformed by the Kimban Orogeny (in the restricted sense of Schwarz, 2003) during 1730-1700 Ma, and was later intruded by early Mesoproterozoic Tickera Granite (1598-1586 Ma), Curramulka Gabbronorite (1589 Ma) and Arthurton Granite (1582 Ma). Neoproterozoic sediments are known to be present on MAITLAND only from drillhole intersections made in the north-eastern part of the map area, and were deposited along the Torrens Hinge Zone marginal to the Adelaide Geosyncline. The units intersected include Rhynie Sandstone, Sturt Tillite and Tapley Hill Formation. The Cambrian Stansbury Basin on Yorke Peninsula is interpreted to have formed on a rifted continental platform on the eastern Gawler Craton; sediments within it up to 2000 m thick are interpreted from seismic surveys. Generally, the Cambrian succession contains three sequence sets and records two local marine transgression and regression cycles. The Cambrian sediments have petroleum potential in the region. Permian diamictite crops out on southern Yorke Peninsula and is widely encountered in drillholes. The diamictite (Cape Jervis Formation) was deposited in glacio-lacustrine, glaciofluvial and restricted marine environments. Tertiary sediments are exposed in the coastal cliffs of the eastern side of Yorke Peninsula and consist of siliciclastics with minor carbonates. Deposition of the overlying Quaternary succession was probably controlled by glacial-eustatic sea level oscillations, resulting in periodic submarine deposition. Several marine transgressions, evidenced by limestone beds of the littoral-pelagic Point Ellen Formation (~1.2 Ma), tidal channel deposits at the base of the Bridgewater Formation (<0.78 Ma), fossiliferous Glanville Formation (~0.125 Ma) and Posidonia-bearing beds of the St Kilda Formation (~6000 years), are recognised. The tectonic development of Yorke Peninsula has been relatively complicated, particularly with respect to the formation of the basement rocks, and interpretation is made especially difficult due to their poor surface exposure. Generally in the region, six major primary rock-forming events can be recognised, relating to deposition of the middle Palaeoproterozoic (1920-1845 Ma Corny Point Paragneiss), the late Palaeoproterozoic (1770-1740 Ma Wallaroo Group), and the Neoproterozoic (~770-700 Ma), Cambrian (~540- 500 Ma), Permian and Tertiary sediments. In terms of regional structural geology, seven rock deformational or shear-faulting events (D1-D7) are recognised in this study.