Anomalously low chemical weathering in fluvial sediment of a tropical watershed (Puerto Rico)

Joo, Young Ji; Madden, M. E. Elwood; Soreghan, Gerilyn S.

doi:10.1130/g40315.1

Cited by 13 publications

(44 citation statements)

References 32 publications

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“…Additional samples included detailed sampling (n = 4, 30 cm apart) of a profile in the middle Salagou Formation that displayed inferred macroscopic pedogenic features and a set (n = 5) of predominant source-rock lithologies (schist, granite, and tuff from the Montagne Noire dome). The chemical index of alteration (CIA; Nesbitt and Young, 1982;Price and Velbel, 2003;Joo et al, 2018)…”

Section: Geochemistrymentioning

confidence: 99%

Loess in eastern equatorial Pangea archives a dusty atmosphere and possible upland glaciation

et al. 2020

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Carboniferous−Permian strata in basins within the Central Pangean Mountains in France archive regional paleoequatorial climate during a unique interval in geological history (Pangea assembly, ice-age collapse, megamonsoon inception). The voluminous (∼1.5 km) succession of exclusively fine-grained red beds that comprises the Permian Salagou Formation (Lodève Basin, France) has long been interpreted to record either lacustrine or fluvial deposition, primarily based on a local emphasis of subaqueous features in the upper ∼25% of the section. In contrast, data presented here indicate that the lower-middle Salagou Formation is dominated by up to 15-m-thick beds of internally massive red mudstone with abundant pedogenic features (microscale) and no evidence of channeling. Up-section, limited occurrences of ripple and hummocky cross-stratification, and mudcracks record the intermittent influence of shallow water, but with no channeling nor units with grain sizes exceeding coarse silt. These data suggest that the most parsimonious interpretation for the Salagou Formation involves eolian transport of the sediment and ultimate deposition as loess in shallow, ephemeral lacustrine environments. Provenance analyses of the Salagou Formation indicate coarse-grained protoliths and, together with geochemical proxies (chemical index of alteration [CIA] and τNa) that correspond respectively to a low degree of chemical weathering and a mean annual temperature of ∼4 °C, suggest that silt generation in this case is most consistent with cold-weathering (glacial and associated periglacial) processes in the Variscan highlands. Together with previous studies that detailed voluminous Permian loess in western equatorial Pangea, this work shows a globally unique distribution of dust at low latitudes that can be linked either directly to glaciated alpine terranes or to reworked and deflated deposits of other types (e.g., fluvial outwash) where fine-grained material was originally generated from glacial grinding in alpine systems. These results further support a revised model for early Permian climate, in which extratropical ice sheets coexisted with a semiarid tropics that may have hosted significant ice at moderate elevation.

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Section: Geochemistrymentioning

confidence: 99%

Loess in eastern equatorial Pangea archives a dusty atmosphere and possible upland glaciation

et al. 2020

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“…The lithogenic corrections cannot exclude inherent physical uncertainties in the interpretation of weathering intensities recorded in sediments, in particular basin topography (Garzanti et al, 2013;von Eynatten et al, 2016;Joo et al, 2018) and provenance (von Eynatten et al, 2016), which give weathering indices only relative (site-and time-specific) values. We attribute certain lateral differences between DO565, DU7, and HK930 cores to site-specific topography and provenance effects.…”

Section: Lateral Correlation Of Weathering Proxiesmentioning

confidence: 99%

Lithological correction of chemical weathering proxies based on K, Rb, and Mg contents for isolation of orbital signals in clastic sedimentary archives

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Hron

et al. 2020

Sedimentary Geology

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“…To assess the weathering intensity properly, chemical loss of the mobile elements and the soil profile's physical erosion should occur at a stable rate in the source areas [64]. Active tectonism and storms may enhance the physical erosion of fresh bedrocks and less altered lower horizons of the soil profile, resulting in a lower estimate of weathering intensities (e.g., [65,66]). In the Neungju Basin, volcaniclastic terrane with high and unstable topography might have been formed in the southern part of the basin in a short time due to intense volcanic activities.…”

Section: Contrasting Geochemical Signatures Of Tectonic Settings and Weathering Intensities In A Nonmarine Basinmentioning

confidence: 99%

Relationships between Alluvial Facies/Depositional Environments, Detrital Zircon U-Pb Geochronology, and Bulk-Rock Geochemistry in the Cretaceous Neungju Basin (Southwest Korea)

et al. 2020

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Zircon U-Pb geochronology and bulk-rock geochemistry analyses were carried out to investigate their relationship with depositional environments of the non-marine Neungju Basin sediments in South Korea. The Neungju Basin was formed in an active continental margin setting during the Late Cretaceous with associated volcanism. Detrital zircon age distributions of the Neungju Basin reveal that the source rocks surrounding the basin supplied sediments into the basin from all directions, making different zircon age populations according to the depositional environments. Mudstone geochemistry with support of detrital zircon U-Pb age data reveals how the heterogeneity affects the geochemical characteristics of tectonic setting and weathering intensity. The sediments in the proximal (alluvial fan to sandflat) and distal (playa lake) environments differ compositionally because sediment mixing occurred exclusively in the distal environment. The proximal deposits show a passive margin signature, reflecting their derivation from the adjacent metamorphic and granitic basement rocks. The distal deposits properly indicate an active continental margin setting due to the additional supply of reworked volcaniclastic sediments. The proximal deposits indicate a minor degree of chemical weathering corresponding to fossil and sedimentological records of the basin, whereas the distal deposits show lower weathering intensity by reworking of unaltered volcaniclastic detritus from unstable volcanic and volcaniclastic terranes. Overall, this study highlights that compositional data obtained from a specific location and depositional environments may not describe the overall characteristic of the basin.

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Anomalously low chemical weathering in fluvial sediment of a tropical watershed (Puerto Rico)

Cited by 13 publications

References 32 publications

Loess in eastern equatorial Pangea archives a dusty atmosphere and possible upland glaciation

Loess in eastern equatorial Pangea archives a dusty atmosphere and possible upland glaciation

Lithological correction of chemical weathering proxies based on K, Rb, and Mg contents for isolation of orbital signals in clastic sedimentary archives

Relationships between Alluvial Facies/Depositional Environments, Detrital Zircon U-Pb Geochronology, and Bulk-Rock Geochemistry in the Cretaceous Neungju Basin (Southwest Korea)

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