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The Amadeus basin of central Australia contains about 11,500 m (38,000 ft) of late Proterozoic to middle Paleozoic (Late Devonian) sediment, generally thickening northward across the basin toward the MacDonnell Range. A complex series of anticlinal structures, some of them fault-bounded, in the north-central part of the basin contains accumulations of hydrocarbons in sediments of Early Ordovician, Cambrian, and late Proterozoic ages. Hydrocarbons have been produced from the Ordovician in two fields, the Palm Valley gas field and the Mereenie gas and oil field.
Study of conodont color alteration to define organic maturation levels and trends is based principally on samples collected from the Early Ordovician (Arenig) Horn Valley Siltstone from both outcrop and subsurface localities. Additional faunas have been recovered from the overlying Early-Middle Ordovician Stairway Sandstone and Stokes Formation.
The conodont color alteration isograds in the Amadeus basin appear to be primarily related to events of the Alice Springs orogeny, when the thick mass of molasse sediments (Pertnjara Group) resulting from erosion of the uplifted Arunta Block was deposited. Anomalies to the conodont color isograds appear to be related to erosion associated with the Rodingan orogeny and also possibly to the effects of salt structures.
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