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The common-Pb isotope composition (207Pb/204Pb vs. 206Pb/204Pb) of detrital K-feldspar was measured on the same clastic units from southeastern Laurentia that were previously characterized by detrital zircon and detrital monazite geochronology for provenance analysis. The purpose is to test a model that invokes late Paleozoic recycling of sediment initially sourced from erosion of exhuming Grenvillian basement in the Neoproterozoic. The approach takes advantage of the difference in Pb isotope compositions between Laurentian and Amazonian cratonic sources documented by previous workers. Neoproterozoic samples sourced from southern Amazonia and central Laurentian basement that serve as controls on methodology plot within Pb isotope space characteristic of their respective sources. K-feldspar in the Cryogenian Ocoee Supergroup in the southern Appalachian orogen falls within the field of Pb isotope compositions defined by south-central Appalachian basement (SCAB). The latter, in turn, exhibits Pb isotope compositions characteristic of Amazonia, because SCAB was transferred to Laurentia from Amazonia during Rodinian assembly. In contrast, K-feldspar in early Cambrian arenite falls within the Laurentian field, indicating a shift in the early Paleozoic to a sediment source from the Laurentian Craton. K-feldspar in Lower Pennsylvanian lithic arenites of the Central Appalachian Basin exhibit Pb isotope compositions that fall within the SCAB field but at higher Pb isotope ratios than in the inferred Ocoee sources. Incorporation of all provenance constraints requires an immediate source that is isotopically more radiogenic than the Ocoee but similar in all other petrologic and geochronologic characteristics, for example, other Cryogenian to Ediacaran units along strike in the Appalachian orogen. The results further demonstrate the importance of having multiple detrital mineral proxies for accurate provenance analysis rather than using detrital zircon geochronology alone. [ABSTRACT FROM AUTHOR]

There is as yet no consensus as to the dominant source of sediment transported to the oceans: the steep tectonically active highlands, or the gently sloping lowlands? In this study, new Pb isotopic analyses of detrital K‐feldspar have been combined with published data to constrain sand supply in the Yangtze River, one of the largest fluvial sediment transport systems on Earth. Tributaries draining southeastern Tibet have predominantly unradiogenic K‐feldspar sand grains. K‐feldspar in the middle Yangtze comprises c. 50% of grains of this kind, confirming that the southeastern Tibetan tributaries are the dominant sediment contributors. K‐feldspars characteristic of tributaries of the middle‐lower reaches are not strongly represented in the trunk Yangtze, indicating that they contribute little sediment. Our study demonstrates that tectonic uplift in southeastern Tibet is the primary control on sand supply. This is consistent with quartz 10Be data and with bulk‐sand petrography, indicating a major contribution of detritus from steep mountainous terrain. [ABSTRACT FROM AUTHOR]

Cenozoic passive margin sediments in Taiwan provide an important natural archive to reconstruct drainage reorganization in eastern China. In this study, we used Pb isotope compositions of detrital K-feldspar to investigate the sedimentary provenance of Cenozoic strata in Taiwan and to constrain fluvial system evolution in eastern China. Eocene to lower Oligocene sandstones in Taiwan are characterized by radiogenic K-feldspar grains (206Pb/204Pb>18.4), indicating that the eastern Cathaysia Block served as the dominant sediment contributor. In contrast, a late Oligocene sample has a Pb isotopic character indistinguishable from that of the Gan River, a major tributary of the Yangtze River. This provenance change is interpreted as the result of headward (westward) migration of the paleo-Min River to the Wuyishan (Wuyi Mountains) during the late Oligocene. Miocene deposits are enriched in relatively unradiogenic K-feldspar (206Pb/204Pb<17.0) which can be reliably traced back to the Dabie and Sulu orogenic belts. Since the early Miocene, the paleo-Yangtze River, mainly draining the Yangtze Craton and the Dabie orogenic belt, delivered a large volume of detritus to the East China Sea Shelf Basin and also to the proto-Taiwan region. [ABSTRACT FROM AUTHOR]

The unusual drainage pattern in the southeastern Tibetan Plateau has been proposed to result from the breakup of a single paleo-Red River system. However, whether there or not was a major early Cenozoic "paleo-Red River" flowing from southeastern Tibet to the South China Sea is still highly debated. In this study, we have used Pb isotopic analyses of detrital K-feldspar to constrain the sedimentary provenance of the Cenozoic deposits from the onshore Jianchuan Basin and offshore Yinggehai and Qiongdongnan basins, and further to decipher the drainage evolution of the upper-middle Yangtze and Red Rivers. Detrital K-feldspar from the Baoxiangsi Formation in the Jianchuan Basin shows an apparent mixture of sand delivery from both the upper Yangtze and Yalong rivers, indicating that there was a river draining the Qiangtang Block and Songpan-Ganzi that used to flow through the Jianchuan Basin during the Eocene. In contrast, K-feldspar Pb isotopes from the Eocene to Pliocene deposits of the Yinggehai and Qiongdongnan basins are different from those of the Jianchun Basin and Yangtze, Salween, and Mekong rivers, but similar to that of the modern Red River. These lines of evidence suggest that major rivers draining southeastern Tibet have not been tributaries of the paleo-Red River and hence, there has been no fluvial connection between southeastern Tibet and the South China Sea since at least the late Eocene. • Sedimentary provenance of the Jianchuan,Yinggehai and Qiongdongnan basins were constrained by Pb-in-K-feldspar. • There was a river draining the Qiangtang and Songpan-Ganzi that used to flow through the Jianchuan Basin during the Eocene. • Sedimentary provenance of the YGHB and QDNB has been similar to the modern Red River since the late Eocene. • No fluvial connection between southeastern Tibet and the South China Sea since at least the late Eocene. [ABSTRACT FROM AUTHOR]

• We apply in-situ Rb-Sr, Ar-Ar, and Pb-isotope analysis to ice-rafted K-feldspar. • Detrital Rb-Sr ages agree well with known onshore bedrock ages. • Our data support mid-Miocene formation of major Antarctic Ice-sheet embayments. The latest generation of Antarctic paleo-ice sheet models, incorporating bedrock paleo-topography, reconstruct the development of substantial ice-sheet embayments during the Mid-Miocene Climate Optimum, a warm period between ∼17–15 Ma ago. Here, we test these models using ice-rafted debris (IRD) recovered from the central Weddell Sea (Ocean Drilling Program Site 113–694). These IRD are entrained by the ice-sheet expanding into the embayment during the cooling associated with the subsequent Mid-Miocene Climate Transition and ultimately delivered to the deep marine sink by iceberg armadas during higher-frequency instability events. Due to the near-absence of heavy minerals in these volumetrically small samples, we utilise the novel in-situ K-feldspar 87Rb/87Sr provenance technique by laser-ablation inductively coupled mass spectrometer equipped with a mass-filtered reaction cell. We combine these single-grain ages with in-situ Pb-isotope analysis, as well as 40Ar/39Ar dating of a subset of grains. Results identify the Antarctic Peninsula and southern Dronning Maud Land as key sediment sources, including grains sourced from within the Recovery subglacial basin. These findings support ice sheet instability consistent with reconstructions of major ice sheet embayments formed by climatic conditions analogous to those predicted by modern anthropogenic warming trajectories. Additionally, in-situ 87Rb/87Sr and Pb-isotope analysis of detrital K-feldspar provide a high-throughput alternative to conventional single grain U-Pb or 40Ar/39Ar analysis, especially in small samples where the heavy mineral fraction is limited or absent. [ABSTRACT FROM AUTHOR]