ANALYSIS OF ICE SPRINGS VOLCANIC FIELD STRUCTURES, BLACK ROCK DESERT, UTAH
The first structure is a previously mapped major fault that strikes 015° for 1.5 km from the Ice Springs Volcanic Field. The fault is a high angle normal fault with probable dip-slip motion and has a minimum displacement of 17.2 m; the fault scarp displays distinct columnar joint sets. Approximately 185 m SE from the mapped southern end of the fault is the beginning of a monocline feature that shows columnar jointing oriented 073°, 28°SE. The monocline feature maps the geographical boundary of two distinct flow systems, and may represent the upward propagation of a normal fault in the area. The second structure is a lava channel extending from Miter Crater. The channel contains basalt mounds that are 6-8 m high and tumuli that are 1-2 m high and 2-4 m long, both of which show radial columnar jointing at their bases. Opening mode fractures, some associated with small monocline features, exhibit 7-30 cm of extension and can be traced connecting the mounds and tumuli in the area. Both the channel wall and mound walls intermittently contain striations indicating oblique-slip to dip-slip movement. The final structures studied are two sets of gaping fissures, one in close geographic proximity to the major fault and one to the lava channel. Continuing south from the southern end of the major fault for 650 m is a long series of gaping subparallel fissures striking 015°. The fissures have a minimum depth of 6.2 m, and show 1.2 to 2.9 m of horizontal extension. The fissure system runs adjacent to a flow boundary but cross-cuts the boundary in several locations. An additional large gaping fissure is subparallel to the lava channel containing the mounds and tumuli. It strikes 017°, is 120 m long, has a minimum depth of 4.3 m, and is widest (4.1 m) at the southern end but disappears to the north.