Quantitative study of the distributary braidplain of the Preboreal ice‐contact Gardermoen delta complex, southeastern Norway

Abstract

This raiscd delta structurc is an ice-contact deltaic complex with a volume of ('. 4.4 .loy m', deposited c. 9500 yr BP in a shallow wide 'fjord' during the retreat o f t h e Scandinavian ice cap. The delta plain lies at an altitude of 200-223 m. It aggraded c'. 20 m above the contemporaneous sea level during a regional marine regression.The braidplain palaeochannel characteristics indicate a peak meltwater discharge of 7-9 10' m'/s. Calculations bascd on a glacial ablation model indicate a mid-summer discharge of c. 5.5 10' m3/s. However, the fluvial topset of the delta has an erosive base whose altitude decreases upstream and indicates stream incision by more the 6 m below the contemporaneous sea level. The deep scour is ascribed to episodic floods over the relatively short delta plain, which exceeded direct ablation-associated discharges. The depositional time-span of the delta is assessed to have been 70 years, calculated from coastal gradient and shoreline displacement curves. The average sedimentation rate of the delta is thereby inferred to have been extremely high, c. 6 . 10' m'lyr. The sedimentation is thought to reflect 'extreme' ice-margin conditions, where the sediment and water discharge was maximized by full-scale ablation, with simultaneous subglacial, englacial and supraglacial sediment and water supply. These conditions might further coincide with an abundant rainfall in the catchment area or the drainage of dammed waters, initiating episodic floods which eroded deep beneath sea level. As a whole, the study illustrates the hydrological conditions of proglacial sedimentation at the front of the rapidly retreating last Scandinavian ice cap. BornOslo. ISSN 0300-9483.

Time‐Lapse GPR Tomography of Unsaturated Water Flow in an Ice‐Contact Delta

“…The foreset progrades in a westward direction and shows a large range in dip directions (178–242°), with dips between 15 and 30°. The topset was deposited in a fluvial environment, consisting mainly of pebbly sand and clasts of a diameter from 0.1 to 0.2 m. The bedding in this unit is subhorizontal (Tuttle et al, 1996; Tuttle and Aagaard, 1996).…”

Secular and catastrophic processes reflected in sediments of the Suchedniów water reservoir, Holy Cross Mountains (Poland)

“…For many years lacustrine sedimentation has been a popular topic amongst numerous scientists, both in Poland (e.g., Wajda & Witkowski, 1985;Malkiewicz & Pazdur, 1995;Zieliński, 2014;Gierszewski, 2018;Żarczyński et al, 2019) and elsewhere (e.g., Gilbert, 1885;Moss, 1972;Tuttle et al, 1997;Bridge, 2003;Fleisher et al, 2003;Postma, 2003). The Old Polish industrial district is an example of such an area where this type of research can find excellent conditions.…”

Glacier margin fluctuations, Skaftafellsjökull, Iceland: implications for sandur evolution

“…At present, most studies of proglacial river adjustment to glacier margin change have been concerned with long-term changes during deglaciation (e.g. Maizels 1983;Clague 1986;Teller 1990;Tuttle et al 1997). Less research has been concerned with river channel planform changes in response to short-term changes in glacier margin position over periods of a few years.…”