The provenance signal of climate–tectonic interactions in the evolving St. Elias orogen: framework component analysis and pyroxene and epidote single grain geochemistry of sediments from IODP 341 sites U1417 and U1418

Abstract

The St. Elias orogen and the Surveyor Fan in the adjacent Gulf of Alaska are a coupled source to sink system recording the interplay of tectonics and variable degrees of glaciation during the collision of the Yakutat terrane with the southern Alaska margin since the Miocene. The Miocene to Holocene sediments of the Surveyor Fan were drilled during IODP expedition 341. The recovered material is used to constrain information on changes in erosion centers during the last 10 Ma to study the impact of climatic and tectonic processes on orogen evolution. Point counting of sand- and silt-sized light framework components and geochemical single grain analysis of heavy mineral groups epidote and pyroxene is applied to analyze patterns of sedimentary provenance of two sites on the distal and proximal Surveyor Fan (Site U1417 and U1418, respectively). The studied sands and silts of Miocene to Pleistocene age are slightly enriched in feldspar (plag >> kf) at the proximal site, compositions at both sites do not show systematical changes with time of deposition. Framework component spectra uniformly reflect the expected active margin provenance. Epidote and pyroxene compositions are very consistent and show no change with time of deposition. Associations of epidote and pyroxene with albite, titanite and pumpellyite are in line with near-shore sources in the Chugach Metamorphic Complex and the metabasite belt at its southern border, and in units of recycled detritus exposed in the fold and thrust belt on the western Yakutat Terrane, respectively. Rock fragments indicate input from mainly metamorphic sources during the Miocene and Pliocene and an increase of input from low-grade metamorphic and sedimentary rocks in the Pleistocene, a finding also indicated by the abundance of epidote and pyroxene. This implies increasing erosion of the near-shore areas of the fold and thrust belt with advance of glaciers to the shore since the Miocene, being enhanced by the onset of the Northern Hemisphere glaciation at the beginning of the Pleistocene. Climate changes connected to the mid-Pleistocene transition did not result in appreciable changes in the petrographic compositions. Glaciers seem to have remained nested in their topographically predefined positions, continuously feeding material with uniform characteristics into the fan.

Plio‐Pleistocene Ocean Circulation Changes in the Gulf of Alaska and Its Impacts on the Carbon and Nitrogen Cycles and the Cordilleran Ice Sheet Development

“…Source studies of terrestrial input to Site U1417 during the PPT and early Pleistocene suggest similar to modern coastal detrital provenance of Alaskan coast and Asia , Horikawa et al, 2015 of the inorganic nitrogen and iron input to Site U1417 (Figure S1). The erosion of lithologies at lower altitudes as the glaciation progresses (Figure S1, Perry et al, 2009;Chapman et al, 2012) is consistent with more recent source interpretations in the GOA (Huber & Bahlburg, 2021).…”

“…Here, we reconstruct marine productivity changes in the Gulf of Alaska (GOA), northeast Pacific, through the mid‐ and late‐Pliocene and early Pleistocene (4.0–1.7 Ma), analyzing sediments from the Integrated Ocean Drilling Program (IODP) Expedition 341 Site U1417 (Figure 1). The proximity of the GOA to the Cordilleran Ice Sheet (CIS, Figure 1), which expanded over this time interval (Gulick et al., 2015; Huber & Bahlburg, 2021; Sánchez‐Montes et al., 2020), allows direct examination of how the evolution of a large ice mass affects the supply of macro/micronutrients via fluvial and glacial transport to the ocean to influence marine productivity (Müller et al., 2018). Based on previous research (Haug et al., 2005; Lawrence et al., 2013), one hypothesis is that the marine productivity in the subarctic Pacific was higher before the iNHG due to increased deep nutrient mixing.…”

Petrology and Petrographic Delineation of Kamlial Formation Sandstone Mong and Thorar Village, Northern Pakistan

“…This method provides detailed insights into the geological processes and environments responsible for sediment formation. In contrast, QFL analysis primarily quantifies the relative abundance of quartz, feldspar, and lithic fragments in sedimentary rocks, offering a simplified yet quantitative assessment of sediment composition (Huber & Bahlburg, 2021). While provenance analysis offers a more comprehensive understanding of depositional history and source materials, QFL analysis provides a quick and standardized method for characterizing sedimentary rocks, particularly in large-scale studies or when detailed mineralogical data is not required (Hussain et al, 2021).…”

Optimal Raman-scattering signal for estimating the Fe3+ content on the clinozoisite–epidote join

“…They occur as typical metamorphic minerals but are also observed in igneous rocks, hydrothermally altered rocks, low-temperature veins, and join fillings (e.g. Deer et al, 1997;Franz and Liebscher, 2004) as well as in ore deposits and in sedimentary rocks derived from orogenic settings (Garzanti and Andò, 2007;Huber and Bahlburg, 2021). Thus, understanding of the compositionparagenesis relation for epidote-supergroup minerals is critical for petrological and geochemical interpretations of a wide variety of rocks.…”