Geology of the north fork of Flodelle Creek drainage basin and surficial uranium deposit, Stevens County, northeastern Washington

Abstract. Over the last glacial cycle, ice sheets and the resultant glacial isostatic adjustment (GIA) rearranged river systems. As these riverine threads that tied the ice sheets to the sea were stretched, severed, and restructured, they also shrank and swelled with the pulse of meltwater inputs and time-varying drainage basin areas, and sometimes delivered enough meltwater to the oceans in the right places to influence global climate. Here I present a general method to compute past river flow paths, drainage basin geometries, and river discharges, by combining models of past ice sheets, glacial isostatic adjustment, and climate. The result is a time series of synthetic paleohydrographs and drainage basin maps from the Last Glacial Maximum to present for nine major drainage basins – the Mississippi, Rio Grande, Colorado, Columbia, Mackenzie, Hudson Bay, Saint Lawrence, Hudson, and Susquehanna/Chesapeake Bay. These are based on five published reconstructions of the North American ice sheets. I compare these maps with drainage reconstructions and discharge histories based on a review of observational evidence, including river deposits and terraces, isotopic records, mineral provenance markers, glacial moraine histories, and evidence of ice stream and tunnel valley flow directions. The sharp boundaries of the reconstructed past drainage basins complement the flexurally smoothed GIA signal that is more often used to validate ice-sheet reconstructions, and provide a complementary framework to reduce nonuniqueness in model reconstructions of the North American ice-sheet complex.

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Multiple controls on sediment grain properties of Peruvian coastal river basins

10.5194/esurf-2017-8 ◽

2017 ◽

Author(s):

Camille Litty ◽

Fritz Schlunegger ◽

Willem Viveen

Keyword(s):

Grain Size ◽

Drainage Basin ◽

River Basins ◽

Humid Climate ◽

Sediment Properties ◽

Peruvian Andes ◽

Southern Group ◽

Gravel Beds ◽

The North ◽

Grain Properties

Abstract. Twenty-one coastal rivers located on the western Peruvian margin were analyzed to determine the relationships between fluvial and environmental processes and sediment grain properties such as grain size, roundness and sphericity. Modern gravel beds were sampled along a north-south transect on the western side of the Peruvian Andes, and at each site the long a-axis and the intermediate b-axis of about 500 pebbles were measured. Morphometric properties such as river gradient, catchment size and discharge of each drainage basin were determined and compared against measured grain properties. Grain size data show a constant value of the D50 percentile all along the coast, but an increase in the D84 and D96 values and an increase in the ratio of the intermediate and the long axis from south to north. Our results then yield better-sorted and less spherical material in the south when compared to the north. No correlations were found between the grain size and the morphometric properties of the river basins when considering the data together. Grouping the results in a northern and southern group shows better-sorted sediments and lower D84 and D96 values for the southern group of basins. Within the two groups, correlations were found between the grain size distributions and morphometric basins properties. Our data indicates that fluvial transport is the dominant process controlling the erosion, transport and deposition of sediment in the southern basins while we propose a geomorphic control on the grain size properties in the northern basins. Sediment properties in the northern and southern basins could not be linked to differences in tectonic controls. On the other hand, the north-south trend in the grain size and in the b/a ratio seems controlled by a shift towards a more humid climate and towards a stronger El Nino impact in northern Peru. But, generally speaking, the resulting trends and differences in sediment properties seem controlled by differences in the complex geomorphic setting along the arc and forearc regions.

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Evidence from 40Ar/39Ar Ages for a Churchill province source of ice-rafted amphiboles in Heinrich layer 2

Journal of Glaciology ◽

10.3189/s0022143000003427 ◽

1996 ◽

Vol 42 (142) ◽

pp. 440-446 ◽

Cited By ~ 1

Author(s):

Roberto H. Gwiazda ◽

Sidney R. Hemming ◽

Wallace S. Broecker ◽

Tullis Onsttot ◽

Chris Mueller

Keyword(s):

North Atlantic ◽

Drainage Basin ◽

Ice Sheets ◽

Bimodal Distribution ◽

Laurentide Ice Sheet ◽

Hudson Bay ◽

Glacial Sediment ◽

The North ◽

Layer 2 ◽

Eastern North Atlantic

Abstract40Ar/39Ar ages of most single ice-ratted amphiboles from Heinrich layer 2 (H2) from a core in the Labrador Sea, a core in the eastern North Atlantic and a core in the western North Atlantic range from 1600 to 2000 Ma. This range is identical to that for K/Ar ages from the Churchill province of the Canadian Shield that outcrops at Hudson Strait and forms the basement of the northern part of Hudson Bay. The ambient glacial sediment includes some younger and older grains derived from Paleozoic, Mesoproterozoic and Archean sources, but still the majority of the amphiboles have ages in the 1600–2000 Ma interval. The Ca/K ratios of these 1600–2000 Ma old amphiboles, however, have a bimodal distribution in contrast with the uniformity of the Ca/K ratios of H2 amphiboles. This indicates that 1600–2000 Ma old amphiboles of the ambient sediment were derived from an additional Early Proterozoic source besides Churchill province. In H2, Churchill-derived grains constitute 20–40% of the ice-rafted debris (IRD). The fraction in the ambient glacial sediment is 65–80%. Results presented here are consistent with the hypothesis that Heinrich events were produced by a sudden intensification of the iceberg discharge through Hudson Strait that mixed, in the North Atlantic, with icebergs that continued to calve from other ice sheets. The shift from mixed sources in the background sediment to a large dominance of Churchill province grains in H2 indicates that, even if calving of other ice sheets intensified during the Heinrich episode, the increase in the iceberg discharge via Hudson Strait from the Hudson Bay drainage basin of the Laurentide ice sheet was by far the largest.

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Use of Wyoming Southern Bighorn Mountains Topographic Map Evidence to Test a Recently Proposed Regional Geomorphology Paradigm: USA

Journal of Geography and Geology ◽

10.5539/jgg.v11n3p1 ◽

2019 ◽

Vol 11 (3) ◽

pp. 1

Author(s):

Eric Clausen

Keyword(s):

Drainage Basin ◽

Water Source ◽

High Elevation ◽

Mountain Range ◽

Topographic Map ◽

The South ◽

New Paradigm ◽

River Drainage ◽

North Fork ◽

Bighorn Mountains

Detailed topographic maps covering a high elevation Bighorn-Powder River drainage divide segment in the southern Bighorn Mountains are used to test a recently proposed regional geomorphology paradigm. Fundamentally different from the commonly accepted paradigm the new paradigm predicts immense south-oriented continental ice sheet melt water floods once flowed across what is now the entire Missouri River drainage basin, in which the high Bighorn Mountains are located. Such a possibility is incompatible with commonly accepted paradigm expectations and previous investigators have interpreted Bighorn Mountains geomorphic history quite differently. The paradigm test began in the high glaciated Bighorn Mountains core area where numerous passes, or divide crossings, indicate multiple and sometimes closely spaced streams of water once flowed across what is now the Bighorn-Powder River drainage divide. To the south of the glaciated area, but still in a Precambrian bedrock region, the test found the roughly adjacent and parallel south-oriented North Fork Powder River and Canyon Creek headwaters located on opposite sides of the Bighorn-Powder River drainage divide with North Fork Powder River headwaters closely linked to a 300-meter deep pass through which south-oriented water had probably flowed. Shallower divide crossings located further to the south suggest diverging and converging streams of water once flowed not only across the Bighorn-Powder River drainage divide, but also across Powder River and Bighorn River tributary drainage divides. The paradigm test also found published geologic maps and reports showing the presence of possible flood transported and deposited alluvium. While unable to determine the water source, the new paradigm test did find evidence that large south-oriented floods had crossed what was probably a rising Bighorn Mountains mountain range.

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