Quantitative reconstruction of palaeohydrology from fluvial stratigraphy provides sophisticated insights into the response, and relative impact, of tectonic and climatic drivers on ancient fluvial landscapes. Here, field measurements and a suite of quantitative approaches are used to develop a four-dimensional (space and time) reconstruction of palaeohydrology in Late Cretaceous palaeorivers of central Utah, USA – these rivers drained the Sevier mountains to the Western Interior Seaway. Field data include grain-size and cross-set measurements and span five parallel fluvial systems, two of which include up-dip to down-dip transects, across seven stratigraphic intervals through the Blackhawk Formation, Castlegate Sandstone and Price River Formation. Reconstructed palaeohydrological parameters include fluvial morphologies (flow depths, palaeoslopes, palaeorelief and planform morphologies) and various hydrodynamic properties (flow velocities, water discharges and sediment transport modes). Results suggest that fluvial morphologies were similar in space and time; median flow depths spanned 2 to 4 m with marginally greater flow depths in southerly systems. Meanwhile palaeoslopes spanned 10⁻³ to 10⁻⁴, decreasing downstream by an order of magnitude. The most prominent spatio-temporal change is an up to four-fold increase in palaeoslope at the Blackhawk–Castlegate transition; associated alluvial palaeorelief is tens of metres during Blackhawk deposition and >100 m during Castlegate Sandstone deposition. This study observed no change in unit water discharges at the Blackhawk–Castlegate transition, which argues against a climatically driven increase in palaeoslope and channel steepness. These findings instead point to a tectonically driven palaeoslope increase, although one limitation in this study is uncertainty in palaeochannel widths, which directly influences total water discharges. These reconstructions complement and expand on extensive previous work in this region, which enables the efficacy of quantitative reconstruction tools to be tested. Comparison of results with facies-based interpretations indicates that quantitative tools work well, but inconsistencies in more complex reconstructions (for example, planform morphologies) highlight the need for further work.

中文翻译：

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从源头到汇重建古河流的形态和水动力：美国犹他州白垩纪西部内陆盆地

从河流地层定量重建古水文学提供了对构造和气候驱动因素对古代河流景观的响应和相对影响的复杂见解。在这里，现场测量和一套定量方法被用于对美国犹他州中部晚白垩世古河流进行四维（空间和时间）重建——这些河流将塞维尔山脉排到西部内陆海道。现场数据包括粒度和交叉集测量，跨越五个平行河流系统，其中两个包括上倾至下倾横断面，跨越穿过 Blackhawk 组、Castlegate 砂岩和 Price River 组的七个地层区间。重建的古水文参数包括河流形态（水流深度、古斜坡、古地形和平面形态）和各种流体动力学特性（流速、排水量和沉积物运输方式）。结果表明，河流形态在空间和时间上相似；中值流动深度跨度为 2 至 4 m，在南风系统中流动深度稍大。与此同时，古斜坡跨越了 10⁻³到 10 ⁻⁴，向下游下降一个数量级。最显着的时空变化是在黑鹰-城堡门过渡处古坡增加了四倍；相关的冲积古地貌在 Blackhawk 沉积期间为数十米，在 Castlegate 砂岩沉积期间为 >100 m。本研究未观察到 Blackhawk-Castlegate 过渡处的单位排水量发生变化，这与气候驱动的古坡度和河道陡度增加相矛盾。这些发现反而指向构造驱动的古坡度增加，尽管本研究的一个限制是古河道宽度的不确定性，这直接影响总水排放量。这些重建补充并扩展了该地区以前的广泛工作，这使得能够测试定量重建工具的功效。结果与基于相的解释的比较表明定量工具工作良好，但在更复杂的重建（例如，平面形态）中的不一致突出了进一步工作的需要。