The EATERINGINNA 1:100 000 scale sheet area is in central Australia with its northern boundary coincident with the South Australian and Northern Territories border. It is located at the eastern end of the Musgrave Ranges and therefore occupies a portion of the north-eastern Musgrave Block. The rocks comprise transitional amphibolite-granulite grade metamorphics granitoids and basic intrusives upon which are developed their clastic derivatives and soils fanned during the late Tertiary and Quaternary. The earliest rocks are layered gneisses of: (a) granitic, granodioritic (predominant), tonalitic, basic (b) calcsilicate and aluminous compositions. Chemical evidence suggests that the first group represents a meta-acid volcanic sequence from which it is inferred that the Musgrave Block is a major volcanic province. The second group (b) is considered to represent minor volcanogenic sediments and contemporaneous derivatives of weathering which include the Aluminous gneisses that are garnet-bearing south of the Marryat Fault Zone and cordierite-bearing to the north. The retrograde reaction: Almandine +sillimanite + quartz = cordierite was controlled as much by fo2, as decreasing pressure. It is suggested that the encroachment of the Kulgeran granitoids was responsible. It is noted from similar suites elsewhere in the world, that cordierite rocks are more highly oxidised than are their garnetiferous counterparts. Postpeak temperatures and pressures obtained from the gneisses give values approximating 750°C at 6.5-7.5 kb. Radiometric dating indicates an early age approximating 16 20 Ma, which may be attributed either to deposition or to an early metamorphic event. There are two definitive structural/metamorphic events during which the gneisses were acutely (E2) and variably (E3) folded. The E3 event coincided with the development of ESE and NE trending fractures of continental magnitude. It is postulated that the gneissic layering resulted from an earlier event or events (E1). Evidence for partial melting comes from the presence of migmatites of pre-, syn- and post- F2 ages. Locally syn-02 granitoids are recognised and the Block was intruded extensively by granitoids during 03. These are the Kulgeran granitoids dated at 1100 Ma which in the vicinity of EATERINGINNA cluster about the NE Ferdinand Fault Lineament and comprise the-' Ferdinand batholith'. Basic intrusives cover a wide chronological span from those now interlayered with gneisses, pre- and post-F2 pyroxenites, peridotites and anorthosites, and syn-03 dolerite dykes and small noritic plutons. The majority of faulting relates to the E3 tectonic event, the first stage of which was semi-ductile in nature, so that fracturing is spatially related to folding; during the latter part of 03, deformation was by fracturing only. The earliest fault lithology is in ductile shears, followed chronologically by mylonites and pseudotachylites, epidotitic fault fills and finally simple breccias. The region shows signs of recent seismic activity and on 30th March 1986 an earthquake of magnitude Ms5.8 produced an arcuate thrust-fault scarp near Gasses bore. There is no obvious evidence of either the Peterman or Alice Springs orogenies although some of the fault breccias could be attributed to these events. No Adelaidean-Mesozoic sediments are in the mapped area although all are represented at the margins of the Musgrave Block. The Tertiary deposits are predominantly pedogenic with thin colluvial, alluvial and lacustrine sediments formed during an interval of deep weathering. These deposits relate to a system of centripetal drainage, and are preserved because of the development of duricrusts (silcrete, ferricrete, calcrete). The Quaternary and present-day deposits are broadly similar to the Tertiary lithologies but apart from minor calcrete, have no duricrust, and represent a change in drainage style from centripetal to one flowing southeastward into Lake Eyre.