1. Gulf of California - Eastern California - Walker Lane: Two major transtensional belts in the Pacific - North America plate boundary Paul Umhoefer, Northern Arizona University Linking MARGINS and EarthScope; lead into discussion…

2. SIMILARITIES IN BOTH BELTS: Major part of plate boundary {but 90-95% vs 20-25% of r.p.m.} Active since 14-12 Ma Formed between batholiths & calderas edge PC crust; on arc Western edge of Basin & Range Transtensional (throughout history?) Strain partitioning - across plate boundary & within belts {margin vs center of belts} Localization of strain over time DIFFERENCES stages of development rates of motion across belts different total offsets (opening) pre-rift crust (Mojave)

3. NATURE OF PRE-RIFTED CRUST: Do older batholith/caldera belts control location-processes of belts? Laramide (Mojave only) effects? Did mid-Tertiary caldera belts effect rifting process? Thermal state of crust? WEST EDGE OF BASIN & RANGE: Do differences in previous extension effect rifting processes? OVERALL STRAIN RATES: Is there a threshold for fundamentally different behavior related to strain rates?

4. Science objectives: how previous crustal structure effects oblique rifting New crust and nature of lower crust in N Gulf of Cal & Salton Kinematic/opening budget across belts = strain rates through time age/nature of oldest rift basins and especially marine initiation failed rifts and jumping of rift centers (really strain localization) obliquity and style of rifting (LANFs) formation of strike-slip and transform faults strain partitioning and fault mechanics role of mantle lithosphere??

5. MARGINS funding in Salton trough - NW Mexico onshore: None? A few NSF-Tectonics grants recently Many studies of neotectonics Fair number of proposals NO proposals for large passive-active seismic transects ala Lizarralde PESCADOR in southern Gulf of California {Fuis et al study - late 1970s} Northern Gulf of Cal will remain a hole for seismic, except CORTEZ

6. Can we merge MARGINS & EarthScope?? {& Continental Dynamics & Core??} 1){USGS - new projects…} 2)Salton trough - Mojave ECSZ as link between belts 3)Comparative studies S to N 4)Different stages of rifting S to N Lizarralde et al 2003 Ewing PESCADERO cruise CORTEZ cruise PESCADERO cruise