| + | Elongate concave upward fold<ref>Vincelette, R. R., E. A. Beaumont, and N. H. Foster, 1999, [http://archives.datapages.com/data/specpubs/beaumont/ch02/ch02.htm Classification of exploration traps], in E. A. Beaumont, and N. H. Foster, Exploring for Oil and Gas Traps: [http://store.aapg.org/detail.aspx?id=545 AAPG Treatise in Petroleum Geology 3], pp. 2-1--2-42.</ref> |