Single-grain post-IR IRSL signals of K-feldspars from alluvial fan deposits in Baja California Sur, Mexico

Brown, Nathan D.; Rhodes, E. J.; Antinao, José Luis; McDonald, Eric V.

doi:10.1016/j.quaint.2014.10.024

Cited by 31 publications

(42 citation statements)

References 28 publications

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“…chronologies in Tables 4 and 5. The temporal distribution of the six new IRSL ages and the C-14 and cosmogenic data is in agreement with that of the chronology presented in Brown et al (2014), and of previous work in the La Paz and San Juan area (Maloney, 2009;Busch et al, 2011;Umhoefer et al, 2014). Further details on interpretation of specific sites are presented below in the respective unit description.…”

Section: Soils Data and Geochronologysupporting

confidence: 88%

“…4). The chronology presented here in addition to that presented in Brown et al (2014) allows us to be confident about the ranges of deposition for the alluvial sediments in the study area. Our interpretation is further supported by consistency of the chronology with that of Maloney (2009) in the Carrizal fault system, western La Paz basin (Fig.…”

Section: Chronology Of Events and Evidence For Discrete Depositional mentioning

confidence: 91%

“…Samples were taken from below the mixing some biological or pedological processes, which was determined by observing soil textural and structural properties in the upper zones of sampled sections, with field determinations being critical to approve a site for luminescence or cosmogenic depth profile sampling. Single grain IRSL methods on sand (180e220 mm size) were preferred because of expected incomplete bleaching in this alluvial setting (Rhodes, 2011;Brown et al, 2014). Pilot samples were used to establish optimal measurement conditions and fading properties (Huntley and Lamothe, 2001;Brown et al, 2014).…”

Section: Methodsmentioning

confidence: 99%

“…Single grain IRSL methods on sand (180e220 mm size) were preferred because of expected incomplete bleaching in this alluvial setting (Rhodes, 2011;Brown et al, 2014). Pilot samples were used to establish optimal measurement conditions and fading properties (Huntley and Lamothe, 2001;Brown et al, 2014). Dose recovery experiments were also performed to validate our approach (Wintle and Murray, 2006).…”

Section: Methodsmentioning

confidence: 99%

“…A direct comparison with cosmogenic age estimates was possible using samples from the same pit profiles. A complete methodological description and discussion of the feldspar luminescence approach is described in Brown et al (2014). Radiocarbon dating was performed on samples obtained from selected sites in younger units.…”

Section: Methodsmentioning

confidence: 99%

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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: Soils Data and Geochronologysupporting

confidence: 88%

Section: Chronology Of Events and Evidence For Discrete Depositional mentioning

confidence: 91%

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

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

Antinao

McDonald

Rhodes

et al. 2016

Quaternary Science Reviews

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Storage and weathering of landslide debris in the eastern San Gabriel Mountains, California, USA: Implications for mountain solute flux

Vecchio

Lang

Robins

et al. 2018

Earth Surf Processes Landf

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The weathering of silicate minerals in mountain landscapes provides a critical source of chemical solutes in the global biogeochemical cycles that sustain life on Earth. Observations from across Earth's surface indicate that the greatest flux of chemical solute is derived from rapidly eroding landscapes, where landsliding often limits the development of a continuous soil cover. In this study, we evaluate how weathering of landslide debris deposits may supplement the chemical solute flux from rapidly eroding, bedrock‐dominated landscapes. We present new measurements of depositional surface and soil morphology, soil geochemistry, and luminescence‐based depositional ages from debris stored in Cow Canyon, a tributary to the East Fork of the San Gabriel River in the eastern San Gabriel Mountains of California. Cow Canyon deposits include locally derived debris emplaced by dry colluvial and debris flow processes. Deposits have planar, low‐angle, sloping surfaces with soils exhibiting a greater degree of weathering than nearby soils formed on bedrock. A ~33–40 ka depositional age of Cow Canyon deposits exceeds the estimated recurrence time for the largest landslides in the San Gabriel Mountains, suggesting the stored landslide debris may be a persistent source of chemical solute in this landscape. To quantitatively explore the significance of landslide debris on the landscape solute flux, we predict the flux of chemical solute from bedrock and debris soils using a generic, time‐dependent model of soil mineral weathering. Our modeling illustrates that debris soils may be a primary source of chemical solute for a narrow range of conditions delimited by the initial landslide debris porosity and the comparative soil age. Broadly, we conclude that while landslide debris may be an important local reservoir of chemical solute, it is unlikely to dominate the long‐term solute flux from rapidly eroding, bedrock‐dominated landscapes. © 2018 John Wiley & Sons, Ltd.

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Geomorphological controls on fluvial carbon storage in headwater peatlands

Alderson

Evans

Rothwell

et al. 2019

Earth Surf Processes Landf

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Geomorphological controls and catchment sediment characteristics control the formation of floodplains and affect their capacity to sequester carbon. Organic carbon stored in floodplains is typically a product of pedogenic development between periods of mineral sediment deposition. However, in organically‐dominated upland catchments with a high sediment load, eroded particulate organics may also be fluvially deposited with potential for storage and/or oxidation. Understanding the redistribution of terrestrial carbon laterally, beyond the bounds of river channels is important, especially in eroding peatland systems where fluvial particulate organic carbon exports are often assumed to be oxidised. Floodplains have the potential to be both carbon cycling hotspots and areas of sequestration. Understanding of the interaction of carbon cycling and the sediment cascade through floodplain systems is limited. This paper examines the formation of highly organic floodplains downstream of heavily eroded peatlands in the Peak District, UK. Reconstruction of the history of the floodplains suggests that they have formed in response to periods of erosion of organic soils upstream. We present a novel approach to calculating a carbon stock within a floodplain, using XRF and radiograph data recorded during Itrax core scanning of sediment cores. This carbon stock is extrapolated to the catchment scale, to assess the importance of these floodplains in the storage and cycling of organic carbon in this area. The carbon stock estimate for the floodplains across the contributing catchments is between 3482‐13460 tonnes, equating on an annualised basis to 0.8‐4.5% of the modern‐day POC flux. Radiocarbon analyses of bulk organic matter in floodplain sediments revealed that a substantial proportion of organic carbon was associated with re‐deposited peat and has been used as a tool for organic matter source determination. The average age of these samples (3010 years BP) is substantially older than Infrared Stimulated Luminesence dating which demonstrated that the floodplains formed between 430 and 1060 years ago. Our data suggest that floodplains are an integral part of eroding peatland systems, acting as both significant stores of aged and eroded organic carbon and as hotspots of carbon turnover. © 2019 The Authors. Earth Surface Processes and Landforms published by John Wiley & Sons Ltd.

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Single-grain post-IR IRSL signals of K-feldspars from alluvial fan deposits in Baja California Sur, Mexico

Cited by 31 publications

References 28 publications

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

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

Storage and weathering of landslide debris in the eastern San Gabriel Mountains, California, USA: Implications for mountain solute flux

Geomorphological controls on fluvial carbon storage in headwater peatlands

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