Late Miocene to Pleistocene Source to Sink Record of Exhumation and Sediment Routing in the Gulf of Alaska From Detrital Zircon Fission‐Track and U‐Pb Double Dating

Abstract

We investigate the late Miocene‐Pleistocene offshore sedimentary record of the Yakutat microplate to evaluate the spatial and temporal variations in rock exhumation and sediment routing patterns at the heavily glaciated and actively converging plate boundary in southeast Alaska. We present 1,456 new fission track ages and 1,372 new U‐Pb ages from double‐dated detrital zircons derived from fourteen samples collected from offshore. We integrate our results with published geochronology and thermochronology data onland and offshore in order to constrain grain provenance. We find that offshore strata deposited east of the fold and thrust belt are sourced from the rapidly exhuming areas along the entire Fairweather Fault, the northeastern part of the syntaxial region, as well as the slowly exhuming Insular superterrane. In contrast, the western strata are sourced from the emerging fold and thrust belt and the Chugach Metamorphic Complex located north of the plate boundary. In these samples we identified a change in sediment provenance, which we suggest marks the capture of the Bagley Ice Valley by the proto‐Bering Glacier at the transition from the early to late Pliocene. This implies that the modern Bagley‐Bering Glacier System is much older than previously known. Strata deposited at ~8.6 Ma suggest that extreme rapid exhumation was already ongoing in the late Miocene, which supports previous findings in deep‐sea deposits. Overall, the data help discern several stages in the evolution of sediment routing patterns in response to dynamic tectonic and surficial processes along this active convergent margin.

Spatiotemporal Evolution of Central Qilian Shan (Northwest China) Constrained by Fission-Track Ages of Detrital Grains from the Huangshui River

“…Based on the assumption that detrital ZFT and AFT ages have not been reset by heating due to modern rivers and/or postdepositional burial in basins, the measured ages relate either to the formation age of a source area or its exhumation history [45,48,[67][68][69]. The present-day thickness of the Xining Basin succession is limited (<3 km) and the regional thermal gradient is low (20-30 • C/km), suggesting low burial temperatures [43].…”

Quantifying the Link Between the Detrital Zircon Record and Tectonic Settings

“…Of these, 1,201 samples were modern sediment (e.g., Campbell & Allen, 2008; Garzanti et al., 2016, 2018; Ibañez‐Mejia et al., 2018; Jacobs et al., 2017; MacDonald et al., 2013; Parra‐Avila et al., 2016; Pepper et al., 2016; Zhong et al., 2017) such that their depositional ages are clearly defined. EDAs in other 4,860 samples were obtained based on various pieces of evidence, including micropaleontology, paleontology, biostratigraphy (e.g., Blum et al., 2018; Bootes et al., 2019; Clift et al., 2019; Hodges et al., 2017; Jaeger et al., 2014; Leary et al., 2020; Zhang et al., 2018), U‐Pb or 40 Ar/ 39 Ar dating of tuffs or volcanic ash deposits (e.g., Abdullayev et al., 2018; Amidon et al., 2017; Kimbrough et al., 2015; Viglietti et al., 2018; Zhang et al., 2019), magnetostratigraphy (e.g., Abdullayev et al., 2018; Amidon et al., 2017; Clift et al., 2019; Kimbrough et al., 2015; Koshnaw et al., 2020; Zhang et al., 2018), depositional facies analysis and stratigraphy (Olierook et al., 2019), and geologic maps (e.g., Hart et al., 2016). EDAs of 2,468 samples in the data set obtained by estimated age intervals (e.g., Abdullayev et al., 2018; Amato et al., 2013; Bootes et al., 2019; Koshnaw et al., 2020) or the stratigraphy of deposition (e.g., to stage stratigraphy) (e.g., Andersen et al., 2016; Craddock et al., 2021; Leary et al., 2020; Lundmark et al., 2014), which were converted to absolute ages as EDAs using the middle of the age intervals and the ICS International Chronostratigraphic Chart (Cohen et al., 2013) in the data set of Puetz & Condie.…”

Volcanic trigger of ocean deoxygenation during Cordilleran ice sheet retreat

“…Previous studies found that the terrigenous sediment provenance on the Southern Alaska margin has been stable since the Pleistocene [84][85][86][87] . This is borne out by the statistically indistinguishable bulk sediment εNd at the intermediate-depth site between the Glacial and the Holocene samples (Fig.…”

“…Next, we define the terrigenous endmembers. Provenance studies based on thermochronology [84][85][86] , zircon geochemistry 84 and heavy minerals 87 show that the Pleistocene terrigenous sediments at the intermediate-depth and abyssal sites are mainly delivered by the Bagley-Bering Glacier system, which brings eroded materials from the Cretaceous-Eocene accretionary complex of the Chugach-Prince William (CPW) terrane 88 . The CPW terrane includes the Valdez and Orca groups consisted mainly of metasedimentary rocks and minor metabasite rocks, with increasing degree of metamorphism toward the Chugach Metamorphic Complex (CMC) eastward in the Saint Elias Mountains.…”