The benthic macro-algae of Georgian Bay, the North Channel and their drainage basin

Hydrobiologia ◽  
1988 ◽  
Vol 163 (1) ◽  
pp. 141-148 ◽  
Author(s):  
Robert G. Sheath ◽  
Julie A. Hambrook ◽  
Christopher A. Nerone
Keyword(s):  
Drainage Basin ◽  
Georgian Bay ◽  
The North ◽  
Macro Algae

scholarly journals Reconstruction of North American drainage basins and river discharge since the Last Glacial Maximum

2016 ◽  
Vol 4 (4) ◽  
pp. 831-869 ◽  
Author(s):  
Andrew D. Wickert
Keyword(s):  
North American ◽  
Drainage Basin ◽  
Ice Sheets ◽  
Glacial Isostatic Adjustment ◽  
Drainage Basins ◽  
Last Glacial ◽  
Isostatic Adjustment ◽  
The North ◽  
The Last Glacial Maximum ◽  
The Last Glacial

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.

scholarly journals Multiple controls on sediment grain properties of Peruvian coastal river basins

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.

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

1996 ◽  
Vol 42 (142) ◽  
pp. 440-446 ◽  
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.

Great Lake Manitoulin: Georgian Bay and the North Channel

Hydrobiologia ◽  
1988 ◽  
Vol 163 (1) ◽  
pp. 1-19 ◽  
Author(s):  
P. G. Sly ◽  
M. Munawar
Keyword(s):  
Great Lake ◽  
Georgian Bay ◽  
The North

Mineralogical evidence for sediment derivation and ice movement within the Wash drainage basin, eastern England

Clay Minerals ◽  
1985 ◽  
Vol 20 (2) ◽  
pp. 209-220 ◽  
Author(s):  
R. D. Wilmot
Keyword(s):  
Recent Work ◽  
Drainage Basin ◽  
Clay Mineralogy ◽  
The South ◽  
River Systems ◽  
The North ◽  
Glacial Periods ◽  
Mineralogical Evidence

AbstractThe Wash drainage basin contains four principal river systems. Samples were collected from the freshwater and estuarine reaches of each of these, and silt- and clay-grade fractions were separated and examined by XRD. The clay mineralogy of each of the rivers is different; in the north the Witham sediments contain chlorite, the Welland and Nene samples contain vermiculite, with a higher proportion of kaolinite in the former, while in the south the Ouse sediments contain smectite. The clay fractions of the samples from the estuarine reaches all contain chlorite, confirming that non-fluvial sources must contribute to the sediments of the Wash. Comparison of this pattern of clay mineralogy with that for the underlying Jurassic and Cretaceous rocks shows that there was relatively little modification during the Pleistocene glacial periods. Such a pattern supports recent work which suggests that ice moved through the Wash gap and then fanned out from the Fenland area, rather than entering the region from the north.

scholarly journals Cenozoic tectonics of the Western Approaches Channel basins and its control of local drainage systems

2011 ◽  
Vol 182 (5) ◽  
pp. 451-463 ◽  
Author(s):  
Pascal Le Roy ◽  
Claire Gracia-Garay ◽  
Pol Guennoc ◽  
Jean-François Bourillet ◽  
Jean-Yves Reynaud ◽  
...  
Keyword(s):  
Sea Level ◽  
Structural Control ◽  
Drainage Basin ◽  
Sedimentary Cover ◽  
Outer Shelf ◽  
English Channel ◽  
The North ◽  
Tectonic Inversion ◽  
Two Stages ◽  
Tectonic Movements

Abstract The geology of the Channel Western Approaches is a key to understand the post-rift evolution of the NW European continental margin in relation with the Europe/Africa collision. Despite considerable evidence of Tertiary tectonic inversion throughout the Channel basin, the structures and amplitudes of the tectonic movements remain poorly documented across the French sector of the Western Approaches. The effect of the tectonic inversion for the evolution of the “Channel River”, the major system that flowed into the English Channel during the Plio-Quaternary eustatic lowstands, also needs to be clarified. Its drainage basin was larger than the present-day English Channel and constituted the source of terrigenous fluxes of the Armorican and Celtic deep sea fans. A lack of high-resolution seismic data motivated the implementation of the GEOMOC and GEOBREST cruises, whose main results are presented in this paper. The new observations highlight the diachronism and the contrast in amplitudes of the deformations involved in the inversion of the French Western Approaches. The tectonic inversion can be described in two stages: a paroxysmal Paleogene stage including two episodes, Eocene (probably Ypresian) and Oligocene, and a more moderate Neogene stage subdivided into Miocene and Pliocene episodes, driven by the reactivation of the same faults. The deformations along the North Iroise fault (NIF) located at the termination of the Medio-Manche fault produced forced folds in the sedimentary cover above the deeper faults. The tectonic inversion generated uplift of about 700 m of the mid-continental shelf south of the NIF. The isochron map of the reflectors bounding the identified seismic sequences clearly demonstrates a major structural control on the geometry of the Neogene deposits. First, the uplift of the eastern part of the Iroise basin during the upper Miocene favoured the onset of a broad submarine delta system that developed towards the subsiding NW outer shelf. The later evolution of the ’palaeovalley’ network corresponding to the western termination of the “Channel River” exhibits a ’bayonet’ pattern marked by a zigzagging pattern of valleys, with alternating segments orientated N040oE and N070oE, controlled by Neogene faulting. The palaeovalley network could have begun during Reurevian or Pre-Tiglian sea-level lowstands, which exposed the entire shelf below the shelf edge. The amplitude of the sea-level fall is assumed to have been magnified by uplift of the Iroise basin, followed by later tilting of the outer shelf, as observed in many other examples documented along the North Atlantic margins.

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