Palaeosols and sequence stratigraphy of the Lower Permian Abo Member, south-central New Mexico, USA

The relationship between palaeosols and sequence stratigraphy is tested in the Lower Permian Abo Member, south-central New Mexico, by comparing interfluve and fluvial-terrace palaeosols with palaeosols that developed within lowstand-fluvial deposits. Interfluve and fluvial-terrace palaeosols consist of primary pedogenic features, including vertical root traces, vertic structures, Stage II and III pedogenic calcite and translocated clay (argillans), which are cross-cut or replaced by low-aluminium goethite, gley colour mottling, sparry calcite veins and ankerite. The polygenetic character of the palaeosols is consistent with initial development for several thousand to tens of thousands of years on well-drained interfluves or fluvial terraces, followed by waterlogging due to invasion by a rising water table that locally may have been brackish. In contrast, lowstand-fluvial sediment that filled incised valleys contains only rooted and vertic palaeosols, whose immaturity resulted from high aggradation rates. Palaeosols similar to those in the Abo Member have been recognized in other ancient strata and, when combined with highresolution correlation, provide evidence for interpretation of sequencestratigraphic surfaces and systems tracts.