FIELD TRIPS

Field trip subsidies are available to GSA Cordilleran Section student members who are registered for a field trip. Deadline to apply: 26 April.

1. Pliocene-Quaternary Tectonic Evolution of the Northern Eastern California Shear Zone.
Mon.-Wed., 24-26 May.
Canceled.
2. Late Proterozoic, Paleozoic and Mesozoic Rocks and Structures in the Victorville-Helendale Region, Mojave Desert, California.
Tues.-Wed., 25-26 May.
Howard Brown, Janis Hernandez contact info ]
We will visit the Victorville region of the Mojave Desert to see a variety of geologic features, including (1) multiple folded and metamorphosed Late Proterozoic and Paleozoic miogeoclinal rocks; (2) folded Lower Jurassic Fairview Valley Formation metasediments that unconformably overlie eroded Paleozoic rocks; (3) Middle Jurassic Lower Sidewinder volcanic rocks; (4) syn- and post-Lower Sidewinder extensional deformation including the Sparkhule Mountain slide, which placed Paleozoic limestones and Early Jurassic Fairview Valley Formation on top of younger lower Sidewinder volcanics; (5) younger Jurassic low-angle extensional and compressional deformation; (6) still younger intrusive rocks, gravity slides/breccia sheets, faulting, and much, much more.
Max.: 18; min.: 10.
Cost: US$270, includes breakfast, 2 lunches, snacks and refreshments, 1 night lodging, and transportation. Stops include easy to moderate hikes to reach outcrops or overview points for discussion and arm waving. New geologic mapping allows greater resolution of geologic details and has allowed complexities not recognized by previous work to be resolved. Numerous large-scale detailed maps will be displayed and discussed.
3. Anatomy of an Anachronistic Carbonate Platform: The Lower Triassic of the southwestern United States and its Relationship to the Recovery from the Permian-Triassic Mass Extinction.
Tuesday, 25 May-Wednesday, 26 May 2010.
Canceled.
4. Soledad and Plush Ranch Basins: Mid-Tertiary Extensional Terrane Dismembered by the San Andreas Fault System.
Sat.-Mon., 29-31 May.
Raymond V. Ingersoll, Eric Hendrix, Ron Cole contact info ]
This trip will revisit two "classic localities" originally identified by John Crowell, Perry Ehlig, and their students during the 1950s through 1970s as evidence for large-magnitude displacements along faults of the San Andreas system. Subsequent detailed work on the sedimentary, volcanic, and structural history and geochronology of these two basins confirms synsedimentary crustal extension during the mid-Cenozoic (26-20 Ma) transition from convergent to transform tectonics. This trip will observe alluvial, rockslide, lacustrine, and volcanogenic deposits, which confirm similar half-graben evolution of both basins, with similar crustal extension direction (N-NW). Synsedimentary detachment faulting has been identified in at least one of the two basins; potential impacts of detachment evolution on sedimentation and subsequent basin deformation will be observed and discussed. Possible geodynamic explanations for crustal extension during the convergent-to-transform transition will be presented. Finally, the relative importance of these offset basins in understanding evolution of the San Andreas fault system will be discussed.
Max.: 40; min.: 15.
Cost: US$255, includes transportation by van; 2 nights lodging (double occupancy); 2 lunches, snacks and drinks; guidebook; does not include dinners or breakfasts.
5. Exploring the Whittier and San Andreas Faults.
Sun., 30 May, 7:30 a.m.-5:30 p.m.
Canceled.
6. Hydrogeology of Icehouse Canyon, San Gabriel Mountains, California.
Sun., 30 May.
Jonathan A. Nourse contact info ]
For hydrogeology and nature enthusiasts, Icehouse Canyon, with its Quaternary deposits, crystal-clear pools and redwoods, is one of Southern California's true gems. This trip explores the geologic reasons for flow variations in Icehouse Creek. Gaining and losing reaches of the creek documented by many years of stream gauge records will be related to vivid geologic controls that include spring discharge from water-saturated landslide deposits, bedrock constrictions of alluvial aquifers, and infiltration into fault-bounded gravel deposits. The morning itinerary involves a moderately strenuous 1.5-mile hike up Icehouse Canyon trail, with multiple stops to view stream-gauging sites and perennial springs. Afternoon stops will contrast Icehouse Canyon watershed with the adjacent Upper San Antonio Canyon watershed, which records markedly different base-flow recession. We will discuss likely reasons for this difference while exploring the Quaternary and bedrock geology near San Antonio Falls and Upper Manker Springs. This excursion takes place during the peak of the runoff season when spring discharge and stream flow are most dramatic.
Max.: 21; min.: 10.
Cost: US$90, includes transportation and parking passes, lunch, and snacks.
7. Quaternary Geology of the San Bernardino Mountains and Their Tectonic Margins.
Sat.-Tues., 29 May-1 June. .
Doug Yule contact info ]
This trip will visit key sites that illustrate the temporal and spatial Quaternary geologic evolution of the San Bernardino Mountains. The Quaternary record here reveals a compelling story of fault reorganization, uplift, and erosion related to oblique convergence at the southern "Big Bend" of the San Andreas fault. The currently active and several abandoned strands of the San Andreas fault bound the range on the southwest. Here, the fault-bounded Yucaipa Ridge block experienced >5 mm/yr of denudation from 0.5 to 0.8 Ma. Other structural blocks in the mountain range have experienced distinct uplift and erosion histories, which will be explored. In San Gorgonio Pass, an ongoing debate about the seismic hazard facing southern California centers on whether through-going rupture of the San Andreas system can occur here. The 1992 Joshua Tree–Landers–Big Bear earthquake sequence revealed the significance of the fault system that bounds the eastern margin of the range. To the north, impressive thrust scarps of the North Frontal fault bound the range but appear to have last ruptured thousands of years ago. Important questions to address on the field trip include (1) can tectonogeomorphic features owing to local block adjustments be distinguished from features owing to broader plate margin interactions; (2) do tectonic structures along the Mojave Desert margin of the range have similar time-space histories as structures along the southeast margin of the range; and (3) what is the evidence for a two-sided uplift history for the San Bernardino Mountains within the broader San Andreas system?
Max.: 30; min.: 15.
Cost: US$260, includes three nights lodging, meals (2B, 3L, 1D), transportation, and field trip guide. Some meals are not included (1B, 2D). Trip participants will have an opportunity to purchase these meals on their own as we travel.
8. Geologic History, Eruptive Stratigraphy and Ongoing Volcanic Unrest at Long Valley Caldera and Mammoth Mountain.
Sun.-Wed., 30 May-2 June.
Wes Hildreth, David Hill, Brandon Browne, Jorge Vazquez contact info ]
Eastern California possesses a rich volcanic history characterized most notably by the cataclysmic caldera-forming eruption of Long Valley ~760,000 years ago and numerous mafic scoria cones, silicic domes, and their associated lavas and pyroclastic deposits near Mammoth Mountain, Glass Mountain, and the Coso and Big Pine volcanic fields. Stops will highlight a revised understanding of the region's volcanic history based on new results from Mammoth Mountain and new studies of Holocene mafic eruptions in the southern Inyo volcanic chain, as well as a review of classic localities where key features of the Bishop Tuff's emplacement history are well preserved. Stops will include the Chalk Bluffs and Owens Gorge, Lookout Mountain, Deadman Creek Dome and flow, Mammoth Mountain (flanks and summit), Horseshoe Lake, and the Big Pine Volcanic Field.
Max.: 20; min.: 8.
Cost: US$410, includes transportation to/from Anaheim, three nights lodging at the Sierra Nevada Aquatic Research Laboratory (SNARL) dormitory, professionally catered meals while at SNARL, and gondola tickets to Mammoth Mountain summit.
9. Monterey Formation of the Los Angeles Basin.
Tues., 25 May, 7 a.m.-6 p.m.
Richard J. Behl, []; Stefano Mazzoni, []
The Miocene Monterey Formation is a distinctly siliceous and organic-rich deposit with stratigraphic equivalents that span much of coastal California and the Pacific Rim. It is California’s primary petroleum source rock and an important reservoir in some areas. It also records key middle to late Miocene climatic, oceanographic, and tectonic transitions. It has been well-studied in the Coast ranges of central California, the Salinas basin, and Temblor range/San Joaquin basin, however, it has been little studied in the highly petroliferous Los Angeles basin. The Monterey and it stratigraphic equivalents - the Puente and Modelo formations underlie and source most of LA's oil fields, however they only outcrop in the uplifted terrains that surround the basin. This field trip will visit key localities of the Monterey Formation in Newport Beach, Crystal Cove State Park and the Palos Verdes Peninsula to examine some of the key lithofacies and see how they differ from better studied areas in California. Field trip is sponsored by the LA Basin Geological Society.
Max.: 50; min.: 12.
Cost: US$90, includes transportation, lunch, and snacks.
10. Sedimentology and Facies Architecture of Channelized Slope System: Capistrano Formation, San Clemente, Southern California.
Wed., 26 May, 7 a.m.-6 p.m.
Kirt Campion; Stefano Mazzoni, [].
Outcrops of the Capistrano Formation located in the vicinity of San Clemente State Beach provide excellent exposures of deep-water channels that were formed in a slope setting and filled with a variety of turbidite lithofacies.  The Capistrano Formation is late Miocene to Pliocene in age and unconformably overlies diatomaceous shales and mudstones of the middle to late Miocene Monterey Formation.  This set of outcrops provides analog data for many seismically resolved confined-channel complexes and provides insight into lithofacies distribution and architectural features at the bed, bed set, channel and channel complex scale.
This trip will focus on the architecture of the Capistrano, which consists of a number of channels and channel complexes, and the distribution of turbidite lithofacies within this architectural framework.  The sandstone-dominated system is about 20 m thick and 1.3 km wide and serves as a model for confined channels that typically are represented seismically by a single cycle.  The Capistrano is made up of laterally amalgamated channels that exhibit a change in net to gross ratio, facies preservation, and bed architecture from the channel margin to channel axis.  Channel margin facies is low net to gross (<50% net), non-amalgamated, thin-bedded, and dominated by low-concentration turbidites (Tbcde).  In contrast, the channel-axis facies is high net to gross (>90%), thick-bedded, amalgamated, and dominated by traction deposition of sand and gravel deposits.
We will walk along the base of sea cliffs to examine exposures, bring comfortable shoes.  You will need a small pack for water and camera (no sampling is allowed, so leave your hammers at home). Field trip is sponsored by the LA Basin Geological Society.
Max.: 35; min.: 10.
Cost: US$90, includes transportation, lunch, and snacks.

 

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