The oil and gas producing structures of the Rocky Mountain area may be classified according to their genetic relationship to major tectonic features. Patterns established by this classification may be helpful in searching for unknown structures. Producing anticlines and domes are considered to be subsidiary or secondary structures which were formed by the same forces and created at the same time as the more obvious large features. Based on past experience, favorable environments for new discoveries may be expected: (1) in the zone of adjustment between mountain uplifts and basin blocks; (2) in front of thrust sheets; (3) above basement faults; (4) as "warps" in broad basin areas; (5) at terminal parts of mountain uplifts or arches; (6) above igneous intrusives. It is sugg sted that by "working backward" from known major tectonic features that subsidiary structures may be found which will be proved effective oil and gas traps.

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