Inherited Grain‐Size Distributions: Effect on Heavy‐Mineral Assemblages in Modern and Ancient Sediments

Abstract

Heavy‐mineral suites are used widely in sandstone provenance and are key when connecting source and sink. When characterizing provenance related signatures, it is essential to understand the different factors that may influence a particular heavy‐mineral assemblage for example, chemical weathering or diagenetic processes. Hydrodynamics, causing size‐density sorting, exert major control on the distribution of heavy minerals. Here, we highlight the effect of grain‐size inheritance, essentially the absence of certain grain sizes within a specific heavy‐mineral species, on two distinct types of sediments. Modern deposits from a high‐energy beach in NW Denmark give an analog for heavily reworked sediment, primarily controlled by hydrodynamic processes. In contrast, three Palaeogene turbidite successions in the Eastern Alps were sampled, presenting a more complex history that includes diagenesis. All samples were processed for their heavy‐mineral compositions using Raman spectroscopy, and several techniques applied to determine the effect of grain‐size inheritance. Results show that (a) even within the hydrodynamically well‐sorted beach and placer deposits, evidence of grain‐size inheritance is apparent, and (b) turbidites of variable heavy‐mineral composition show strong effects of grain‐size inheritance for several mineral species. Moreover, considerable intersample contrasts within single turbidite beds are observed. We enforce the importance of understanding grain‐size inheritance, as well as other processes effecting size‐density relations in clastic sediment that go well beyond purely hydrodynamic control of intrasample heavy‐mineral variability.

Heavy‐Mineral Grain Counting: Counting Techniques, Error Estimation, and the Number of Grains to be Counted

“…The heavy-mineral composition of sample series AC, EY62, SF-1, HMR, and JS-NGO are published (Chaudhuri et al, 2023;Dunkl et al, 2020;Feil et al, 2024;Schönig et al, 2023). This dataset is extended by the heavymineral composition of sample series JS-Erz and BOH, both presented here for the first time.…”

“…Evaluation sheets for the individual samples and grain-size fractions from the original literature sources and the newly presented data were compiled, mineral classes were unified, and all grains classified as "opaque," "not identified," "potential contaminants" (i.e., moissanite and corundum, except for sample series HMR where corundum is a natural component), "light minerals" (i.e., quartz, feldspars, feldspathoids, cordierite, zeolites), "carbonates," "sulfates," and "phyllosilicates" were removed. In addition, "TiO 2 (other)" (i.e., all TiO 2 phases other than rutile) were removed from sample series SF-1, because these were evaluated as mostly authigenic (Feil et al, 2024). For the considered 65 aliquots, this results in a dataset of 80,393 transparent heavy-mineral grains (Table S1 in Schönig (2024)).…”

“…Seventeen aliquots are from Chaudhuri et al (2023) and belong to nine Jurassic Cretaceous sandstone samples from three different sub-basins in the Kutch Basin of India (labeled AC). Twenty aliquots are from Feil et al (2024). Seven of those are from three samples of a modern-sand beach placer in Vorupør, Denmark (labeled EY62).…”