Sandstone-body geometry and hydrostratigraphy of the northern High Plains Aquifer system, USA

Korus, Jesse T.; Joeckel, R.M.

doi:10.1144/qjegh2021-171

Cited by 3 publications

(1 citation statement)

References 92 publications

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“…Irregular paleotopography, laterally variable sedimentation patterns, and multiple periods of aggradation and degradation during this period resulted in stratigraphic discontinuities (Ludvigson et al, 2009;Swinehart et al, 1985;Tedford, 2004). Lower Ogallala Group sediments filled a series of paleovalleys atop the sub-Ogallala surface, forming vertically and laterally amalgamated channel bodies ~50 m in thickness and as much as 20 km in width (Korus & Joeckel, 2022;Swinehart et al, 1985). Strata atop these paleovalley fills and atop paleouplands are generally sheet-like, recording alluvial plain deposits (Joeckel et al, 2014) and, to the south, eolian sand sheets and loesses (Gustavson & Winkler, 1988).…”

Section: Geologic Settingmentioning

confidence: 99%

Telescopic Megafans on the High Plains, USA Were Signal Buffers in a Major Source-To-Sink System

Korus,

Joeckel

2023

The Sedimentary Record

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Sediment routing systems transport sediment and environmental signals inefficiently. The storage and recycling of sediment buffers the responses of sedimentary systems to tectonic, climatic, and geomorphic changes. Long-term ( >106 a.) storage may occur in megafans—large, low-relief, hemiconical fluvial deposystems—but the behavior of these systems over such timescales is unclear. We examine late Neogene megafan deposits on the High Plains, USA that are stored in the catchment of the continental-scale Rocky Mountain-Gulf of Mexico source-to-sink system. Using high-resolution elevation data, we map numerous fluvial ridges (inverted channel relics) that can be differentiated into five, chronologically distinct groups. The oldest four groups comprise radial arrays with multiple channel divergences (avulsion nodes). The inferred fan apices and longitudinal intersection points are offset successively downgradient, indicating that fanhead entrenchment and fan-lobe deposition were approximately contemporaneous and strongly suggesting a telescopic morphology. The youngest group of channels, also the lowest in elevation, is confined to terraces along the modern valley of the South Platte River. We interpret this group as direct evidence for the abandonment of the megafan and the incision of the present valley. Uplift was the chief driving mechanism for early telescoping, but channel widening and uniform downcutting in the younger groups suggest that change in stream power was the primary driver of later telescoping and incision. The storage of sediment in the megafan effectively decoupled sources from downstream sinks. Some of this sediment was recycled during entrenchment, but much of it remains in storage as the Ogallala Group and Broadwater Formation. Emplacement of telescopic megafans should be considered as a long-term ( ≥106 years) buffer in other modern and ancient sediment routing systems.

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Section: Geologic Settingmentioning

confidence: 99%

Telescopic Megafans on the High Plains, USA Were Signal Buffers in a Major Source-To-Sink System

Korus,

Joeckel

2023

The Sedimentary Record

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Exhumed fluvial landforms reveal evolution of late Eocene–Pliocene rivers on the Central and Northern Great Plains, USA

Korus

Joeckel

2023

Geosphere

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Cenozoic strata on the Great Plains are the products of a long-lived, continental sediment routing system, and yet strikingly little is known about these ancient rivers. This article details the discovery of ~3100 fluvial ridges—erosionally inverted alluvial-fan, channel-fill, channel-belt, and valley-fill deposits—extending from the Rocky Mountain front to the eastern margin of the Great Plains. The direct detection of these channel bodies reveals new insights into late Eocene–Pliocene drainage evolution. Late Eocene–Oligocene streams were morphologically diverse. Alluvial fans adjacent to the Rocky Mountain front changed eastward to parallel or downstream-divergent, fixed, single-thread, straight to slightly sinuous (S = 1.0–1.5) streams <50 m in width. At ~100 km from the Rocky Mountain front, streams became sinuous and laterally mobile, forming amalgamated channel bodies as much as 3 km in width. Streamflow in all these systems was highly dispersed (southeast to northeast) and temporally variable. These characteristics reveal a nascent Great Plains alluvial apron hosting small, poorly integrated drainages undergoing abrupt changes. By the Miocene, more uniform streamflow generally trended east-northeast. Channel deposits are identifiable 500 km from the Rocky Mountain front. Middle Miocene valley fills gave way to fixed, multithread channels a few kilometers in width by the late Miocene. These patterns evince a mature alluvial apron hosting bigger rivers in well-integrated drainages. We interpret the systematic changes between fixed and mobile channel styles to record spatially and temporally variable aggradation rates. The widening of channels in the late Miocene likely reflects increased discharge relating to wetter climates upstream or the integration of once-isolated Rocky Mountain drainage basins into a continental-scale drainage system.

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Using numerical modelling to test the geological and groundwater conceptual understanding of a complex, layered aquifer: a case study from the Fell Sandstone, Northumbria

Bianchi

Collins²,

Ford

et al. 2023

QJEGH

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Groundwater abstractions from the Carboniferous Fell Sandstone, Northumbria, north-east England, provide water supply to the Berwick-upon-Tweed area. Management of these abstractions, totalling 6.5 Ml/day, by the water company along with the regulator for sustainability issues is required. Groundwater abstraction takes place from different sandstone units, which are separated by mudstones, with monitored groundwater heads showing variable responses to system stresses. To improve understanding of this complex system, various activities have been undertaken. Geological mapping and interpretation have been conducted to characterise the nature, geometry, and interconnection of the sandstone units, along with the superficial deposits. Recharge modelling has used to quantify inputs to the system and to understand the long-term water balance. A time-variant model has been implemented to simulate groundwater flow in the sandstone units and to quantify the groundwater balance. The work confirms that the Fell can be split into seven discrete sandstone units, separated by low permeability mudstones, but they are not necessarily laterally connected. There is a range of timescales of groundwater response to recharge events from slow (six months) to very rapid (∼1 day). These findings confirm the complexity of this groundwater system and offer lessons for similar sandstone systems in the UK and worldwide. Thematic collection: This article is part of the Hydrogeology of Sandstone collection available at: https://www.lyellcollection.org/cc/hydrogeology-of-sandstone

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Sandstone-body geometry and hydrostratigraphy of the northern High Plains Aquifer system, USA

Cited by 3 publications

References 92 publications

Telescopic Megafans on the High Plains, USA Were Signal Buffers in a Major Source-To-Sink System

Telescopic Megafans on the High Plains, USA Were Signal Buffers in a Major Source-To-Sink System

Exhumed fluvial landforms reveal evolution of late Eocene–Pliocene rivers on the Central and Northern Great Plains, USA

Using numerical modelling to test the geological and groundwater conceptual understanding of a complex, layered aquifer: a case study from the Fell Sandstone, Northumbria

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