A classification of channel-reach morphology in mountain drainage basins synthesizes stream morphologies into seven distinct reach types: colluvial, bedrock, and five alluvial channel types (cascade, step pool , plane bed, pool rime, and dune ripple). Coupling reach-level channel processes with the spatial arrangement of reach morphologies, their links to hillslope processes, and external forcing by confinement, ripar­ ian vegetation, and woody debris defines a process-based framework within which to assess channel condition and response potential in mountain drainage basins. Field investigations demonstrate character­ istic slope, grain size, shear stress, and roughness ranges for different reach types, observations consistent with our hypothesis that alluvial channel morphologies reflect specific roughness configurations ad­ justed to the relative magnitudes of sediment supply and transport ca­ pacity. Steep alluvial channels (cascade and step pool) have high ratios of transport capacity to sediment supply and are resilient to changes in discharge and sediment supply, whereas low-gradient alluvial channels (pool rime and dune ripple) have lower transport capacity to supply ra­ tios and thus exhibit significant and prolonged response to changes in sediment supply and discharge. General differences in the ratio of transport capacity to supply between channel types allow aggregation of reaches into source, transport, and response segments, the spatial distribution of which provides a watershed-level conceptual model linking reach morphology and channel processes. These two scales of channel network classification define a framework within which to in­ vestigate spatial and temporal patterns of channel response in moun­ tain drainage basins.

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Channel-reach morphology in mountain drainage basins

A review of the braided-river depositional environment

Eleven paleogeographic maps and a summary ice retreat map outline the history of advance, retreat, and readvances of the Laurentide Ice Sheet along with associated changes in proglacial drainage and relative sea level oscillations for Late Wisconsinan and Holocene times. The text outlines pertinent chronological control and discusses the paleoglaciology of the ice sheet, with attention to location and migration of ice divides, their attendant domes and saddles, and to ice streams, ice shelves, and mechanisms of deglaciation. At 18 ka the ice sheet consisted of 3 sectors with an interlocked system of ice divides joined at intersector saddles. A throughgoing superdivide is recognized and named the Trans Laurentide Ice Divide. The ice sheet retreated slowly from 18 to 13 ka, mainly along the west and south margins, but still held a near maximum configuration at 13 ka. A regional change in flow pattern over the Prairies just before 14 ka is thought to represent a large reduction in ice volume, but not in extent, and likely was triggered by a switch from nondeforming to deforming bed conditions. Retreat between 13 and 8 ka was vastly more rapid in the west than in the east, which resulted in eastward migration of the divide system of Keewatin Ice but relatively static divides of Labrador and Foxe Ice. By 10 ka the Trans Laurentide Ice Divide had been fragmented as Hudson Ice became increasingly autonomous. By 8 ka Hudson Ice had disappeared, little ice was left in Keewatin, but Foxe Ice still held its near maximum configuration and Labrador Ice was still larger than Foxe Ice. Repeated surging along aquatic margins and calving back of margins thinned by surging probably was the most important mechanism of deglaciation of Keewatin and Hudson Ice. The core of Foxe Ice disintegrated at 7 ka but retreat and readvance of Foxe Ice remnants continued throughout the Holocene.

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Late Wisconsinan and Holocene History of the Laurentide Ice Sheet

https://www.fs.fed.us/rm/pubs/rmrs_gtr074.pdf

Sampling surface and subsurface particle-size distributions in wadable gravel- and cobble-bed streams for analyses in sediment transport, hydraulics, and streambed monitoring

Bar formation and sediment distribution patterns were examined in a 4-mile braided reach of the upper Kicking Horse River at Field, British Columbia, which is mainly supplied by meltwater from icefields straddling the continental divide at the British Columbia-Alberta boundary in the southeastern Canadian Cordillera. Marked diurnal variations in discharge, suspended sediment concentration, and water temperature occur during peak summer melting periods when rates of sediment transport and bar formation are greatest. Bed material is mostly limestone and dolomite gravel which undergoes rapid fining in the downstream direction. Gravel bars occurring in a wide variety of shapes and sizes comprise the dominant bed forms. Most exposed braid bars have undergone complex depositional and erosional histories and rarely show simple or consistent patterns of grain size or structures, either internal or superficial. Active bars with simple histories and predominantly depositional morphologies are termed "unit bars." Fo...

Sedimentology and Bar Formation in the Upper Kicking Horse River, a Braided Outwash Stream

Nature of Esker Sedimentation

Sediments and bed forms from three braided outwash plains and one steep non-braided mountain stream in the Rocky Mountains of Alberta are compared to sediments and structures exposed in a paleo-out...

Sediments and Bed Forms on a Braided Outwash Plain

A model of the stratigraphy of sequences in coal, based on a subsurface case study of the coal-bearing Lower Cretaceous Mannville Group of Canada, posits basinward progressive splitting patterns of thick, regionally extensive paralic coal seams. Successive splits bounded by transgressive-regressive coal-seam couplets are interpreted to be fourth-order sequences produced in single base-level cycles. Stacked in a progradational pattern, these fourth-order sequences in turn form third-order sequences. Thick, regional seams form on top of a prograding platform by amalgamation of several fourth-order sequences. Vertical profiles of coal properties (geochemistry, petrology, and palynology) in the lower and upper leaves of a split seam which constitute a transgressive-regressive couplet would yield characteristic signatures revealing their transgressive and regressive nature, respectively.

Coal seam splits and transgressive-regressive coal couplets: A key to stratigraphy of high-frequency sequences

In the subsurface of central Alberta, four palynostratigraphic zones are erected in the Ostracode Zone (Aptian-Albian) and adjacent strata of the Mannville Group, based on the dinoflagellate and miospore assemblages from 134 samples from 22 wells within the Edmonton Embayment. The Edmonton Embayment is a shallow, wide paleotopographic depression infilled with muddy sediments of a lagoon/tidal flat complex overlain by a sandy, flood-tidal deltaic complex. The filled embayment was twice inundated by an advancing sea. A complex relationship between lithostratigraphic and palynostratigraphic units is evident. Paleoecological curves based on palynological assemblages from three key wells (one located outside the embayment) indicate relative sea-level fluctuations. Three minor cycles occur within a major transgressive event terminating near the top of the Ostracode Zone, close to the Aptian-Albian boundary.

An Integrated Lithostratigraphic and Palynostratigraphic Study of the Ostracode Zone and Adjacent Strata in the Edmonton Embayment, Central Alberta

The stratigraphic boundary separating the Mannville and the Colorado groups in Alberta, occupying incised valleys cut within the Upper Mannville strata, has previously been interpreted as an unconformity recording post-Mannville erosion followed by a late Albian marine transgression initiated by the deposition of the Joli Fou Shale and locally by the Basal Colorado Sandstone (both of the Colorado Group). Sedimentology, paleontology, organic and inorganic geochemistry, mineralogy, and petrography of strata above and below the unconformity or the sequence boundary have been studied in 106 samples from 37 wells within the Cessford Field covering an area of 3600 km2. Cores through the boundary show a distinct physical break represented by a scoured surface overlain by basal conglomerates. Paleontological data, based on dinoflagellates and foraminifers, show establishment of restricted marine conditions in the Basal Colorado times (initial transgression) and onset of open marine condition (maximum flooding) du...

Indranil Banerjee

Papers

Nature of Esker Sedimentation

Sediments and Bed Forms on a Braided Outwash Plain

Coal seam splits and transgressive-regressive coal couplets: A key to stratigraphy of high-frequency sequences

An Integrated Lithostratigraphic and Palynostratigraphic Study of the Ostracode Zone and Adjacent Strata in the Edmonton Embayment, Central Alberta

An integrated subsurface study of the Mannville–Colorado group boundary in the Cessford Field, Alberta