LAUSR

Fault-related fold models that illustrate the geometry and kinematic development of petroleum traps and structures are frequently used to assist basin exploration and development of structurally complex oil fields. Worldwide, several petroleum-rich provinces are situated in convergent strike-slip settings with adjacent convergent structures that are commonly petroleum traps. Strain studies and modeling of these settings are dominated by the wrench fault model, and examples from the San Andreas fault plate boundary and its trapping influence on adjacent large oil fields in California abound (Wilcox et al., 1973). Use of this model in petroleum exploration and geologic education is problematic and can lead to poor choices and wasted drilling dollars. Here, we show at three field trip stops that the wrench model and its associated flower structures (Harding, 1976) and palm tree structures (Sylvester and Smith, 1976; Sylvester, 1988) fail to explain the oil trapping style and structure of the uppermost crust near the San Andreas fault (Figure 1). Figure 1. Map of southern and southern-central California showing the three field trip stops, petroleum basins, oil fields, the San Andreas fault (SAF), and many of the regional cross section lines constructed by Namson and Davis since 1988. Oil fields are dominantly trapped by young, convergent structures that are the result of late Cenozoic transpression along the SAF plate boundary, which will be demonstrated at the field trip stops. Stop 1 is at the Wheeler Ridge oil field and the convergent San Emigdio Mountains, Stop 2 is along the western big bend segment of the SAF, and Stop 3 is at the Russell Ranch oil field and the convergent Caliente Range. The Neogene basins of southern California are very oil prolific (with a cumulative production of nearly 20 billion bbl of oil and daily production now at 560,000 BOPD). Much of the …