Masters Thesis

Superposed Mesozoic deformations, southeastern Inyo Mountains, California

Mapping in the Nelson Range and the adjacent southeastern Inyo Mountains shows that this area has experienced at least two episodes of early Mesozoic deformation which produced two sets of folds in Mississippian through Permian rocks. A later Mesozoic event may be represented by faults in this area. The older fold set (F1) consists of generally northeast-trending, upright to southeast-overturned folds. A younger fold set (F2) is superimposed upon and locally refolds F1 folds. F2 consists of generally northwest-trending, upright to northeast-overturned folds with steeply southwest-dipping axial plane cleavage. Truncation of some F2 folds by the Hunter Mountain batholith in the Nelson Range indicates that both fold sets are pre-Middle Jurassic in age. The style of F2 folds along portions of the intrusive contact suggests that emplacement of the batholith locally appressed and deflected pre-existing folds. Based on their orientation, sense of vergence and relative age, F1 folds are believed to be temporally and structurally related to the Last Chance thrust system (Middle (?) Triassic to Early Jurassic). F2 folds are correlated with other northwest-trending fo1ds of pre-Middle Jurassic age which occur throughout the ranges immediately east of the Sierra Nevada. Some northwest-striking faults in this area apparently are intruded by dikes of the Independence swarm and thus may be pre-Late Jurassic in age. If so, these faults may be related to a broad, northwest-trending zone of fractures and left-slip faults of Middle to Late Jurassic age which trends obliquely across this region.

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