Full title: FT26CD06. Alluvial Fan Stratigraphy of Southern Baja California
Leader(s): Jose Luis Antinao; Eric McDonald
Endorser(s): GSA Quaternary Geology and Geomorphology Division
CEUs: 2.4
Date(s): Sat–Mon, 25–27 Apr.
Location: La Misión Hotel, Loreto, Baja California Sur, Mexico (trips ends in San Jose del Cabo)
Start Time: 8 a.m.(first day)
End Time: 5 p.m.(last day)
Description: The purpose of this 3-day post-conference field trip is to explore the Late Quaternary alluvial fan sequence developed in the San Jose and La Paz basins in the southern Baja California peninsula. Our trip starts in Loreto (AM, April 25) and ends in San Jose del Cabo (PM, April 27), with two nights lodging in La Paz. We will visit key sites where (1) fan sedimentology and landforms can be observed and discussed, and (2) it is possible to link these features to high energy, hyperconcentrated flows derived from intense and long duration tropical storm precipitation events. At La Paz—capital of Baja California Sur—discussion about the role of large storms in shaping urban history of the city will be highlighted with a visit to a section of the sediments left by Tropical Storm Liza in 1976. These key exposures were used to advance the hypothesis that these sediment packages are unique paleoenvironmental records, helping us to interpret older sequences as markers of enhanced tropical storm activity during the Late Quaternary. At San Jose, we will review evidence for high discharge and sediment flux preserved in bedform stratigraphy. We will discuss how soil development played a key role in defining distinct climatic events and fan history. Stops will include discussion of strategies chosen for dating stratigraphy (i.e., soil chronosequence, luminescence, TCN) in this challenging arid environment. We will link this work with similar recent research in central Baja California and to paleoclimate records in the Mojave and Sonoran Deserts.
Considerations: The area is crisscrossed by roads and highways. We are aiming to have most of the stops to be in close reach of the cars/vans, with short walks over gravel/dirt roads. Given that some of the roads are narrow, vans will be preferable to a bus. There are highway stops and gas stations with reasonable accommodations (water, food available, restrooms) along the route. The city of La Paz, where we can stay overnight, has plenty of services. The trip will end ~5pm on Monday, April 27 near San Jose del Cabo, so participants should plan any accommodations and return flights accordingly.
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Product Code: FT26CD06
Product Category: FTRIP