Classification and Nomenclature of Rock Units

Stratigraphy and coal resources of the Makarwal area, Trans-Indus Mountains, Mianwali District, Pakistan

“…Siwalik Group Lewis (1937, p. 197) proposed a classification for the Siwalik Group following the principles of stratigraphic classification of Ashley and others (1933). His classification, generally accepted by the writers, has been modified to comply with the Stratigraphic Code of Pakistan.…”

Geology of the Arabian Peninsula; southwestern Iraq

“…The system of rock-unit classification and naming employed by Iraq Petroleum Company geologists is advocated in the code of rules compiled by Ashley and others (1939) as supplemented in recent papers and rulings of the Commission on Stratigraphy.…”

The Phosphoria, Park City, and Shedhorn formations in the western phosphate field

“…The latter objective needs no special justification, for, because it aims at the understanding of the lateral relationships and extent of rock units information that has great economic and scientific value it is one of the prime objectives of most stratigraphic work. Similarly, no special defense is required for the formal recognition of unmappable members and tongues because this is common, approved practice (Ashley and others, 1933). In some fringe areas, such as northwestern Wyoming, where the three Permian formations intertongue but are not mappable separately, we do not propose that all the formations be mapped separately.…”