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Studying the centennial or millennial timescale response of large rivers to changing patterns in precipitation, discharge, flood intensity and recurrence, and associated sediment erosion is critical for understanding long‐term fluvial geomorphic adjustment to climate. Long hydrographs, maintaining reliable Flow Duration Curves (FDCs), are a fundamental input for such simulations; however, recorded discharge series rarely span more than a few decades. The absence of robust methodologies for generating representative long‐term hydrographs, especially those incorporating coarse temporal resolution or lacking continuous simulations, is therefore a fundamental challenge for climate resilience. We present a novel approach for constructing multi‐century hydrographs that successfully conserve the statistical, especially frequency analysis, and stochastic characteristics of observed hydrographs. This approach integrates a powerful combination of a weather generator with a fine disaggregation technique and a continuous rainfall‐runoff transformation model. We tested our approach to generate a statistically representative 300‐year hydrograph on the Ninnescah River Basin in Kansas, using a satellite precipitation data set to address the considerable gaps in the available hourly observed data sets. This approach emphasizes the similarities of FDCs between the observed and generated hydrographs, exhibiting a reasonably acceptable range of average absolute deviation between 6% and 18%. We extended this methodology to create projected high‐resolution hydrographs based on a range of climate change scenarios. The projected outcomes present pronounced increases in the FDCs compared to the current condition, especially for more distant futures, which necessitates more efficient adaptation strategies. This approach represents a paradigm shift in long‐term hydrologic modeling. Plain Language Summary: River hydrographs are key inputs for understanding long term Earth surface processes. Due to the limited lengths of observational streamflow records, various techniques were previously developed with limited capabilities to generate representative long hydrographs. Through a novel integrated approach, we are able to construct robust high‐resolution hydrographs on multi‐century timescales, based on developing a linkage between hydroclimatic forces and watershed characteristics within a stochastic framework. We used this methodology to generate a 300‐year high‐resolution hydrograph with satisfactory correlation with the observed FDC. Due to the stochastic background of this framework, the deviation between the observed and generated FDCs was estimated to fall within a reasonable range of 6% and 18%. This framework was extended to provide hourly runoff projections for several future climatic models. Median projections for the near‐term period 2040–2069 demonstrated less deviation from reference data set compared to those for the more distant future 2070–2099. This study represents a scientific shift for long‐term simulations through re‐constructing past, simulating present, or projecting future hydrographs. Key Points: Introducing a novel framework designed to generate statistically robust hydrographs on multi‐century timescales for long‐term simulationsIntegrating a weather generator and a disaggregation technique within a rainfall runoff model to achieve high‐temporal resolution hydrographsUtilizing multiple climate models to evaluate the impacts of climate change on hourly runoff responses [ABSTRACT FROM AUTHOR]

Sedimentary records of lipid biomarkers such as leaf wax n -alkanes are not only influenced by ecosystem turnover and physiological changes in plants, they are also influenced by earth surface processes integrating these signals. The integration of biomarkers into the sedimentary record and the effects of integration processes on recorded environmental signals are complex and not fully understood. To determine the depositional constraints on biomarker records in a high-altitude small catchment system, we collected both soil and stream sediments along a 1000 m altitude transect (1500 – 2500 masl) in the Areguni Mountains, a subrange of the Lesser Caucasus Mountains in Armenia. We utilize the existence of a treeline at ~ 2000 masl, which separates alpine meadow above from deciduous forest below, to assess the relative contribution of upstream biomarker transport to local vegetation input in the stream. We find that average chain length (ACL), hydrogen isotope (δD) and carbon isotope (δ13C) values of n -alkanes are significantly different in soils collected above and below the treeline. However, samples collected from the stream sediments do not integrate these signals quantitively. As the stream drops below the treeline, the ACL, δD and δ13C values of n -alkanes preserved in streambed sediments reflect a bias toward n -alkanes sourced from trees. This suggests that there is either 1) minimal transportation of organic matter from the more open vegetation in higher elevations, or 2) greater production of target biomarkers by trees and shurbs found at lower elevations results in overprinting of stream signals by local vegetation. Though this latter observation may preclude using n -alkanes to measure past treeline movement in these mountains, δD values of biomarkers in fluvial deposits in these settings are more likely to record local hydrological changes rather than changes in upstream fractionation differences associated with vegetation turnover. [ABSTRACT FROM AUTHOR]

The Frasnian-Famennian boundary interval is exposed in New York State in an outcrop belt that stretches from Lake Erie eastward to Steuben County, continuing into Pennsylvania. Recent biostratigraphic examination of brachiopods and conodonts suggested that the shallower water sections to the east have been miscorrelated with the deeper water sections to the west. Revised correlations place the Upper Kellwasser extinction event (Frasnian-Famennian boundary) within the Canaseraga Formation and the Lower Kellwasser extinction event (Pipe Creek Formation) above the Wiscoy Formation. We review these revised correlations and provide additional support based on δ13Corg profiles from several sections. We also define new members in the Wiscoy Formation (Rossburg Member) and Canaseraga Formation (Hornell, Elkhorn Creek, and Crooked members) that should facilitate discussions of faunal and paleoenvironmental changes associated with the Frasnian-Famennian extinctions in the Appalachian Basin. [ABSTRACT FROM AUTHOR]

We reconstruct ancient temperature and elevation gradients across the early Eocene (52-49 Ma) northern Sierra Nevada (California, United States) using organic molecular proxies that record atmospheric and ground-level effects of topography. Paleoelevation was determined by reconstructing the change in the hydrogen isotopic composition of precipitation ([DELTA][delta][D.sub.precip]) and mean annual temperature ([DELTA][T.sub.GDGT]) (glycerol dialkyl glycerol tetraethers) from the isotopic composition of fossil angiosperm leaf n-alkanes and the distribution of microbially produced soil tetraethers preserved in leaf-bearing sediments. Organic molecular data produce equivalent range-scale ([delta][D.sub.n-alkane]) and channel ([T.sub.GDGT]) paleoelevation estimates that show the northern Sierra Nevada was a warm (>6-8[degrees]C warmer than modern), high-elevation (>2 km), and moderate-to low-relief landscape at the Eocene Climatic Optimum. Modern northern Sierra Nevada topography likely reflects post-Paleocene reduction of mean surface elevation and late Cenozoic increases in relief. doi: 10.1130/G30215.1

Author(s): Anders Meibom (corresponding author) [1]; Norman H. Sleep [2]; C. Page Chamberlain [1]; Robert G. Coleman [1]; Robert Frei [3]; Michael T. Hren [1]; Joseph L. Wooden [4] The [...]

Palaeoclimate data indicate that Earth surface temperatures have remained largely temperate for the past 3.5 Byr despite significantly lower solar luminosity over this time relative to the present day. There is evidence for episodic early and late Proterozoic glaciation, but little evidence of glaciation in the intervening billion years. A prolonged equable Mesoproterozoic Earth requires elevated greenhouse gas concentrations. Two endmember scenarios have been proposed for maintaining global warmth. These include extremely high pCO2 or more modest pCO2 with higher methane concentrations. This paper reports on the δ13C of organic matter in 1.1 Ga stromatolites from the Copper Harbor Conglomerate (CHC) of the Mesoproterozoic Midcontinent Rift (North America) and δ18O and Δ47 temperatures of inorganic stromatolite carbonate to constrain formation and burial conditions and the magnitude of ancient carbon isotope discrimination. CHC sediments have never been heated above ~125–155°C, providing a novel geochemical archive of the ancient environment. Stromatolite Δ47 data record moderate alteration, and therefore, the occluded organic matter was unlikely to have experienced significant thermal alteration after deposition. The δ13C values of ancient mat organic matter and inorganic carbonate show isotope discrimination (εp) values ~15.5–18.5‰, similar to modern microbial mats formed in equilibrium with low concentrations of dissolved inorganic carbon. In combination, these data are consistent with a temperate climate Mesoproterozoic biosphere supported by relatively modest pCO2. This result agrees with Atmosphere‐Ocean Global Circulation Model reconstructions for Mesoproterozoic climate using 5–10 times present atmospheric levels pCO2 and pCH4 of >28 ppmv. However, given marine modelling constraints of CH4 production that suggest pCH4 was below 10 ppm, this creates a methane paradox. Either an additional source of CH4 (e.g. from terrestrial ecosystems) or another greenhouse gas, such as N2O, would have been necessary to maintain equable conditions in the Mesoproterozoic. [ABSTRACT FROM AUTHOR]

The Barstow Formation (ca. 19-13 Ma) of southern California, USA, is a terrestrial sequence known for its diverse Miocene mammalian faunas. The formation spans the Middle Miocene Climatic Optimum (MMCO; 17-14 Ma) and offers the opportunity to study environmental change during the last major interval of global warming of the Cenozoic. We combined isotopic analyses of carbon and hydrogen from sedimentary n-alkanes and bulk soil organic matter with analysis of phytoliths (plant silica) and diatoms to reconstruct vegetation composition, habitat structure, and moisture dynamics through the formation. The δ13C and δD of long-carbon-chain n-alkanes derived from terrestrial plants and preserved in sediments of the Barstow Formation record drying prior to the MMCO and through the Middle Miocene Climatic Transition (MMCT; beginning ca. 14 Ma), punctuated by increased moisture in fluvial environments during the peak of the MMCO. Variable isotopic results relate to changes in moisture, driven partly by facies, vegetation composition, tectonic activity, and climatic variability coinciding with intervals of high pCO2. Phytolith assemblages are dominated by forest indicators in riparian habitats during the MMCO, and grass morphotypes constitute significant components of phytolith assemblages after the MMCO, indicating a shift to drier, more open-canopy habitats. The establishment of dry, wooded grasslands in the Barstow Basin coincides with the beginning of the MMCT and cooling sea-surface temperatures in the Pacific Ocean. Our results indicate that moist, closed-canopy habitats formed in southern California during climatic warming, followed by savannah during climatic cooling and the shift to seasonal precipitation regimes. [ABSTRACT FROM AUTHOR]

The effect of tectonic uplift on chemical weathering rates in twelve catchments along the Skykomish River in the Washington Cascades is measured. The chemical weathering rates in the Cascades are controlled by the rate of rock erosion and factors that influence the depth of the active weathering zone.