Crack Systems Analysis of the McCartys Flow, New Mexico, USA

The McCartys Flow is a 3.9-ka vesicular porphyritic basalt lava flow in the Zuni-Bandera Volcanic Field (ZBVF) near Grants, New Mexico. The Lava Falls area on the southern part of the flow is dominated by pahoehoe sheet flows. Topographic features such as plateaus, depressions, monoclines, escarpments, and en-echelon cracks are interpreted as being formed by inflation. Using detailed observations of the Lava Falls area and differential GPS (DGPS) transects, the crack systems of these topographic features were constrained to three different crack patterns. Particular crack patterns were constrained to flow margins and depressions. Analysis of crustal and structural widths along transects indicates that up-swelling was likely responsible for crack formation, though this extension was not necessarily constant. A model of emplacement is suggested to explain the progression of inflation along the flow in a plateau-like fashion of decreasing elevation from the McCartys vent. Finally, the results of the McCartys Flow fieldwork and analysis are discussed as a possible approach examining suspected inflation features in the Elysium Volcanic Province on Mars.