Lanterna Rally

Author: Steve Foster

Publisher:

Published: 2004-08-01

Total Pages:

ISBN-13: 9781881308171

The 2004 NPS field trip concentrates on breccias in the Great Basin. Breccias are significant reservoirs in many petroleum basins worldwide. The oil production at Eagle Springs, Nevada's first field, and in one of the states newest fields, Ghost Ranch, apparently comes from a landslide breccia. The Great Basin breccias are of three types. The first is impact breccias. Dr. John Warme and his colleagues from the Colorado School of Mines and the United State Geological Survey have compiled a substantial amount of evidence to confirm that an extraterrestrial impact occurred during deposition of the Middle Devonian Guilmette Formation. The effects of this collision can be seen over a wide area in Nye and Lincoln Counties. The breccia, named the Alamo Breccia, should provide an exceptional time line for correlations within that area. Additionally, the single graded bed might be a significant reservoir as well.The second type of potential reservoir is the collapse breccias developed during paleokarsting and paleocave development. Like the Alamo Breccia, the collapse breccias also occur in the Devonian Guilmette Formation. To date, the collapse breccias have been identified in northern Nye County and southern Eureka and White Pine Counties and are probably related to a forebulge developed by the Antler Orogeny. Should the associated paleocaves be open in the subsurface and oil filled, they could have astounding production potential like those of the fields in west Texas.The last type of Great Basin breccia to be considered is landslide breccias. These are not "potential reservoirs" but are actual features that can be found in both Eagle Springs and Ghost Ranch Fields. Like the previous two types, these also involve the Devonian Guilmette Formation as well as the Pennsylvanian Ely Limestone. As such, they are real, proven exploration targets in the Great Basin.