Issues

ON COVER – Pre-folding J1 (tilted) and synto post-folding J2 (vertical cross-fold) joints cutting turbidite beds in the Devonian Brallier Formation of the Valley and Ridge in West Virginia (see Table 2 and Datashare 129 of Engelder and Behr, p. 669–694, this issue of the Bulletin). This set of J1 joints is an example of bed-normal joints which, when unfolded, strike between east-northeast and east-west in several formations of the Appalachian Basin from Alabama to Pennsylvania. The mystery of J1 joints is the lack of mineralization and lack of evidence for slip when subject to shear stress during folding.