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Glacial geology
Published in Barry G. Clarke, Engineering of Glacial Deposits, 2017
Glaciofluvial deposits are terrestrial sediments deposited from flowing water either on (channels), within (tunnels), beneath (tunnels) or beyond the ice margin. The water and suspended sediment cause further abrasion of the suspended particles and sides of the channels/tunnels adding to the suspended load. Debris is carried as suspended load or bed load. The sediment can be deposited subglacially in tunnels in the ice or channels in the underlying sediment, along ice margins and beyond the ice margin. These deposits are often subject to further glacial or fluvial actions. It is difficult to determine the amount of sediment carried by meltwater streams but, given the scale of the deposits beyond the ice margin, it is substantial. Sedimentation beyond the ice margin follows the same process as conventional fluvial deposits. The discharge is seasonal and, because the water is cooler and therefore more dense and viscous than that in conventional fluvial processes, the settling rate of the suspended load is less, which means the suspended load is carried further. Close to the ice margins, the glaciofluvial deposits are coarse, poorly sorted clasts. The deposits become finer with distance from the ice margin as the velocity of the flow reduces. The pattern of flow also changes from a braided channel sequence to a single channel. Glaciofluvial deposits can be extensive either as valley in fill or outwash fans in lowland areas. Glaciofluvial deposits occur throughout glaciated regions and are a valuable source of sands and gravels.
Muonionalustaite, Ni3(OH)4Cl2·4H2O, a new mineral formed by terrestrial weathering of the Muonionalusta iron (IVA) meteorite, Pajala, Norrbotten, Sweden
Published in GFF, 2021
Dan Holtstam, Luca Bindi, Andreas Karlsson, Johan Söderhielm, Anders Zetterqvist
The Muonionalusta meteorite represents one of the oldest (4.56 Ga) known solid objects in the Solar system, and broke off from the parent asteroid at about 400 Ma in a cataclysmic cosmic impact event (Holtstam et al. 2003; Blichert-Toft et al. 2010). Muonionalusta is a fine octahedrite, group IVA, which fell to Earth in the Pleistocene, fragmented in the atmosphere and dispersed over a large area (e.g., Lagerbäck & Wickman 1997). The present geographical distribution corresponds to a significant (at least 25 × 15 km), SSE-NNW oriented disturbed strewn field. The predominant Quaternary deposits of the area are till and peat, but vast parts are covered with glaciolacustrine and glaciofluvial deposits (Fagerlind 1981). Remnants of meteorite fragments are scattered in soil and regolith, from the ground surface down to at least four metres of depth. They have endured at least one glacial cycle (the Weichselian) as the fall is deemed ≥115 ka old (Hättestrand 2009). From areal and size distribution of hundreds of samples in the mass range 1–1200 kg, it has been suggested that glacial transport from the original impact area has occurred by up to 8–20 km (Hättestrand 2009). Since the last deglaciation of the area, at around 10 ka BP, the meteorite fragments have experienced yearly freeze-and-thaw cycles in a sub-arctic climate where ground frost may penetrate down to 2.5 m during winters.
Multitechnique approach for characterizing the hydrogeology of aquifer systems: application to the Mauricie region of Québec, Canada
Published in Canadian Water Resources Journal / Revue canadienne des ressources hydriques, 2023
Yan Lévesque, Julien Walter, Lamine Boumaiza, Mélanie Lambert, Anouck Ferroud, Romain Chesnaux
The region’s relief strongly influenced the glacial retreat, and the topography is marked by lineaments composed of ridges and depressions oriented mainly N–S, NNE–SSW, and NE–SW. For example, glaciofluvial deposits were deposited in valleys, thalwegs, and slopes (Prichonnet, Doiron, and Cloutier 2007). In the highlands, these deposits are outcropping and fill the valleys; however, in Piedmont and St Lawrence Lowlands, they are covered by clayey Champlain Sea sediments, which can be overlain by deltaic, lacustrine, alluvial, and eolian sediments locally.