Riverice as a taphonomic agent: an alternative hypothesis for bone artifacts
An intuitive taphonomic model is developed to explain how riverice of temperate and high-latitude rivers may affect bones, and to predict the modifications expected. Partial testing of the model by experiments designed to simulate river breakup
produced bone modifications such as fractures, flakes, facets, striations, isolated cuts, and polish. The taphonomic effects of riverice must be discounted prior to the interpretation of such features as human in origin.
Yhdysvaltain luoteisosan geologinen kehitys ja Columbia-joen altaan suuret luonnonkatastrofit. (Geological evolution of the northwestern United States and catastrophic events in the Columbia River Basin)
Amérique du Nord ; Canada ; Cascade Range ; Columbia River Basin ; Etats-Unis ; Géographie de l'Amérique ; Géomorphogenèse ; Montagne ; Quaternaire ; Quaternaire zones moyennes ; Vallée
During the last glaciation the Cordilleran Ice Sheet covered the upper course of the Columbia River and part of the Columbia Plateau. A large ice-dammed lake called Glacial Lake Missoula was formed in Montana, when an ice lobe plugged a valley
in Idaho. Once the water level in the ice lake had risen to a certain height the ice dam collapsed and draining of the ice lake resulted in a gigantic flood. A new ice dam was then formed, and after some time a further catastrophic flood occurred. It has
An assessment of the erosion potential of the fluvial thermal process during ice breakups of the Lena River (Siberia)
Asian part of Russia ; Bank erosion ; Fluvial dynamics ; Ice breakup ; Inundation ; Lena ; Model ; Peak discharge ; Periglacial features ; Permafrost ; Sakha ; Stream
During the initial stage of ice breakup of the Lena River (Yakutia, Siberia), ice pushes up onto the river banks and produces large accumulations of ice and sediments that protect the islands' heads against the mechanical and thermal effects
of the river's flow. This initial stage is relatively short and terminates only a few days after breakup begins. In the second phase of flooding, after the riverice has melted, the island heads become free of ice. Hence, when water levels are high
of the banks of the river islands displayed high interannual variation that is attributed to the variability of the duration and timing of the flood season.
Pollen and macrofossil analyses of two radiocarbon dated lake sediment cores in the upper Peace River district were used to investigate the controversial late-glacial geochronology of the ice-free corridor between the Laurentide and Cordilleran ice
masses. The data support occlusion or near occlusion of Laurentide and Cordilleran ice in the Peace River area during the late Wisconsin. The sediment record began around 12,000 yr BP in the ice-damned and enlarged Boune Lake. An initially open, sedge
Sandstones and conglomerates formed by precipitation of CaCO3 under stagnant ice sheet
Conglomerate ; Inland ice ; Lithology ; Lower valley ; Poland ; Quaternary ; Rock ; Sandstone ; Sedimentary ; Sedimentary rock ; Wisła
Quaternary sandstones and conglomerates found on the valley-sides of the lower Vistula River have been identified as a product of precipitation of CaCO3 under stagnant Middle-Vistulian ice sheet. The trigger mechanizm of precipitation of CaCO3 has
been attributed to the degassing of CO2 from carbonate-saturated pressure pore water at the bottom of desintegration crevasses and fissures of the stagnant and down-wasting ice sheet. - (DG)
Lake-ice blisters, Terra Nova Bay area, Northern Victoria Land, Antarctica
Antarctica ; Ice ; Lake ; Periglacial features ; Permafrost ; Salinity
-ice blisters in the study area differ from icing blisters described from the northern hemisphere. The latter are caused by hydraulic pessures and are found at locations such as river beds or spring sites on sloping terrain. The Antarctic lake-ice
Ice blisters develop annually on perennially frozen lakes in Northern Victoria Land. They are believed to be caused by hydrostatic pressures generated through progressive freezing of solute-rich water beneath the lake-ice cover during winter. Lake
Geomorphologic and lithologic evidence for an expanded mountain ice sheet on Mount Kenya during the early Quaternary
The analysis and interpretation of pre-Brunhes (>.73 -.79 my) glacial landforms in the Nithi River Basin, on the eastern flank of Mount Kenya, provide evidence for the dynamics of early Quaternary ice. - (L'A.).
Conglomerate ; Inland ice ; Lithology ; Lower valley ; Poland ; Quaternary ; Rock ; Sandstone ; Sedimentary ; Sedimentary rock ; Wisła
Quaternary sandstones and conglomerates found on the valley-sides of the lower Vistula River have been identified as a product of precipitation of CaCO3 under the stagnant Middle-Vistulian ice sheet. The model of precipitation of CaCO3 is attributed
to the degassing of CO2 from pressure pore waters at tje bottom of disintegration crevasses and fissures of the stagnant and downwasting ice sheet. - (DG)
-covered conditions. A field survey was carried out in early March 2008 in a small meandering reach of the Neigette River, which is part of the catchment system of the Mitis River, Quebec. The friction imposed by the ice cover results in parabolic shaped
The AA. compare macroturbulent coherent structures (MCS) geometry and organization between ice covered and open channel flow conditions. Velocity profiles were obtained using a Pulse-Coherent Acoustic Doppler Profiler in both open channel and ice
velocity profiles. Reynolds stresses in the streamwise (u) and vertical (v) components of the flow show positive values near the channel bed and negative values near the ice cover, with 2 distinctive boundary layers with specific turbulent signatures
discontinued and nested close to the boundary walls in ice-covered conditions.
Palaeoflood hydrology of the lower Umgeni River from a reach south of the Inanda Dam, Natal
Flood ; Little ice age ; Natal ; Palaeogeography ; Palaeohydrology ; South Africa ; Stratigraphy
Criteria for the recognition of palaeofloods were developed on the basis of the major 1987 flood. Superfloods in the Little Ice Age are suggested. - (AJC)
The Horton River breakthrough and resulting geomorphic changes in a permafrost environment, Western Arctic Coast, Canada
and delta building would have been rapid. Construction of the delta has protected the adjacent sea cliffs from wave erosion. Attention is paid to the nature of geomorphic change in a permafrost environment and the role of river and sea ice in affecting
Dendrochronological analysis and radiocarbon dating show that a break through to the sea occurred along the lower course of the Horton River after 1640 AD. At the breakthrough site, the Horton River flowed 10 m above sea level so that river erosion
Ice thickness, ablation, and other glaciological measurements on Upper Fremont Glacier, Wyoming
Glacial ablation ; Glacier ; Glaciology ; Ice core ; Meteorology ; Palaeo-environment ; Temperature ; United States ; Wyoming
Glaciological investigations of the Upper Fremont Glacier in the Wind River Range of Wyoming were conducted during 1990-1991. The glaciological data will provide baseline information for monitoring future changes to the glacier and support ongoing
research utilizing glacial-ice-core composition to reconstruct paleoenvironmental records. The results of glaciological and meteorological investigations are presented and discussed in this paper.