Late Pleistocene (Last Interglacial) terrace deposits, Bahia Coyote, Baja California Sur, México

Forbis, Teresa DeDiego; Douglas, Robert G.; Gorsline, Donn S.; Nava-Sánchez, Enrique H.; Mack, Lawrence E.; Banner, Jay L.

doi:10.1016/j.quaint.2004.01.004

Cited by 24 publications

(16 citation statements)

References 23 publications

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“…Similar deposits on the western La Paz Bay (outside of the area covered by Fig. 2) have been dated to 128e130 ka (Forbis et al, 2004), all temporally related to a marine highstand during the interglacial Marine Isotope Stage (MIS) 5e. We therefore interpret the age of the Qt1 deposits to be~120e130 ka (the age of marine highstand during interglacial stage 5e) because of the lack of soil formation in the well-preserved coral rubble that is interstratified within the alluvium.…”

Section: Unit Qt1mentioning

confidence: 73%

Late Pleistocene-Holocene alluvial stratigraphy of southern Baja California, Mexico

Antinao

McDonald

Rhodes

et al. 2016

Quaternary Science Reviews

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a b s t r a c tA late Pleistocene to Holocene alluvial stratigraphy has been established for the basins of La Paz and San Jos e del Cabo, in the southern tip of the Baja California peninsula, Mexico. Six discrete alluvial units (Qt1 through Qt6) were differentiated across the region using a combination of geomorphologic mapping, sedimentological analysis, and soil development. These criteria were supported using radiocarbon, optically stimulated luminescence and cosmogenic depth-profile geochronology. Major aggradation started shortly after~70 ka (Qt2), and buildup of the main depositional units ended at~10 ka (Qt4). After deposition of Qt4, increasing regional incision of older units and the progressive development of a channelized alluvial landscape coincide with deposition of Qt5 and Qt6 units in a second, incisional phase. All units consist of multiple 1e3 m thick alluvial packages deposited as upper-flow stage beds that represent individual storms. Main aggradational units (Qt2-Qt4) occurred across broad (>2 km) channels in the form of sheetflood deposition while incisional stage deposits are confined to channels of~0.5 e2 km width. Continuous deposition inside the thicker (>10 m) pre-Qt5 units is demonstrated by closely spaced dates in vertical profiles. In a few places, disconformities between these major units are nevertheless evident and indicated by partly eroded buried soils. The described units feature sedimentological traits similar to historical deposits formed by large tropical cyclone events, but also include characteristics of upper-regime flow sedimentation not shown by historical sediments, like long (>10 m) wavelength antidunes and transverse ribs. We interpret the whole sequence as indicating discrete periods during the late Pleistocene and Holocene when climatic conditions allowed larger and more frequent tropical cyclone events than those observed historically. These discrete periods are associated with times when insolation at the tropics was higher than the present-day conditions, determined by precessional cycles, and modulated by the presence of El Niño-like conditions along the tropical and northeastern Pacific. The southern Baja California alluvial record is the first to document a precession-driven alluvial chronology for the region, and it constitutes a strong benchmark for discrimination of direct tropical influence on any other alluvial record in southwestern North America.

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Section: Unit Qt1mentioning

confidence: 73%

Late Pleistocene-Holocene alluvial stratigraphy of southern Baja California, Mexico

Antinao

McDonald

Rhodes

et al. 2016

Quaternary Science Reviews

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“…The U-Th age control for QII terraces in the study area is from Porites panamensis corals from three terraces in the northern area that were dated by DeDiego-Forbis et al (2004). In the present study, Chione mollusk shells were collected from these same three terraces, within ~2 m of the collection sites of the coral.…”

Section: Elevation and Age Of Uplifted Marine Terraces And Coastal Upmentioning

confidence: 93%

“…Ages of Quaternary marine terraces were estimated by analyzing the extent of racemization in amino acids preserved within carbonate fossils of the mollusk genus Chione following the methods of Wehmiller and Miller (2000). Amino acid racemization ratios were corroborated by comparison to U-Th ages reported for marine terraces in the northern part of our study area (DeDiego-Forbis et al, 2004), and then these ages were used with the terrace heights to determine surface uplift rates and inferred offset. Racemization is a fi rst-order reversible reaction with a rapid initial rate followed by a signifi cantly decreasing rate (Kennedy et al, 1982;Wehmiller and Miller, 2000).…”

Section: Offshore Chirp and Marine Terrace Methodsmentioning

confidence: 99%

“…In the present study, Chione mollusk shells were collected from these same three terraces, within ~2 m of the collection sites of the coral. DeDiego-Forbis et al (2004) reported U-Th ages of 109-209 ka on the corals, which had initial 234 U values in excess of modern seawater, indicating an open system and uncertainty in the ages. Therefore, DeDiego-Forbis et al (2004) used the approach of Gallup et al (1994), which resulted in terrace ages of 128 ± 2 ka.…”

Section: Elevation and Age Of Uplifted Marine Terraces And Coastal Upmentioning

confidence: 99%

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Late Quaternary faulting history of the Carrizal and related faults, La Paz region, Baja California Sur, Mexico

et al. 2014

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The southwest margin of the Gulf of California has an array of active normal faults despite this being an oblique-divergent plate boundary with spreading centers that localized deformation along the plate boundary 2-3 million years ago. The Carrizal and Centenario faults form the western border fault of the Gulf of California marginal fault system within and south of La Paz Bay, and ~20-30 km west of the capital city of La Paz, Baja California Sur, Mexico. Geologic and geomorphic mapping, optically stimulated luminescence (OSL) geochronology, and paleoseismic investigations onshore, compressed high-intensity radar pulse (CHIRP) profi ling offshore, and analysis of uplifted marine terraces in the footwall of the offshore Carrizal fault provide some of the fi rst numerical and geometrical constraints on late Pleistocene-Holocene faulting along the Carrizal fault. The onshore Carrizal fault has ruptured with up to ~1-2 m of vertical displacement per event, likely producing ~M 6.3-6.9 earthquakes, and at least two to three surface rupturing earthquakes have occurred since 22 ka. Onshore paleoseismic excavations and uplifted marine terraces on the western side of La Paz Bay both suggest offset rates of 0.1-0.2 mm/yr, with a footwall uplift rate of 0.13 mm/yr since 128 ka, and an approximately constant rate since marine oxygen-isotope stage (MIS) 11 terraces (420 ka). A CHIRP survey identifi ed underwater fault scarps with heights ranging from 21 to 86 m on the Carrizal fault in La Paz Bay and from 3 to 5 m along the Centenario fault. The offshore Carrizal fault lies 8-10 km east of the western edge of La Paz Bay, forming a right step from the onshore Carrizal fault. The offshore Carrizal fault is the oldest fault of the fault system, and the fault likely grew in the latest Miocene to Pliocene in a complex way to the south toward the onshore Centenario and Carrizal faults. When the Alarcon spreading center started its modern rates at 2.4 Ma, the Carrizal fault likely slowed to the 0.1-0.2 mm/yr rates of the late Quaternary determined in this study.

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“…The region has a microtidal range of 0.5 to 1 m. Notches have developed along the peninsula in andesitic lahar and lava flow deposits (Hausback, 1984;Aranda-Gomez and Perez-Venzor, 1988;Bellon et al, 2006) composed of very resistant, poorly-stratified, sand-sized detritus, with angular clasts of up to 1 m or more in diameter. Rates of uplift in this region since the last interglacial are thought to have been between 0.12 and 0.15 mm yr − 1 (Mayer and Vincent, 1999;DeDiego-Forbis et al, 2004).…”

Section: Study Areamentioning

confidence: 99%

Cliff notch formation along the sub-tropical La Paz Peninsula, Southern Baja California, Mexico

et al. 2015

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Late Pleistocene (Last Interglacial) terrace deposits, Bahia Coyote, Baja California Sur, México

Cited by 24 publications

References 23 publications

Late Pleistocene-Holocene alluvial stratigraphy of southern Baja California, Mexico

Late Pleistocene-Holocene alluvial stratigraphy of southern Baja California, Mexico

Late Quaternary faulting history of the Carrizal and related faults, La Paz region, Baja California Sur, Mexico

Cliff notch formation along the sub-tropical La Paz Peninsula, Southern Baja California, Mexico

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