An anisotropy of magnetic susceptibility (AMS) fabric record of till kinematics within a Late Weichselian low Baltic till, southern Sweden

Abstract

Herein we report on the results of an anisotropy of magnetic susceptibility (AMS) fabric case‐study of two Late Weichselian tills exposed in a bedrock quarry in Dalby, Skåne, southern Sweden. The region possesses a complex glacial history, reflecting alternating and interacting advances of the main body of the Scandinavian Ice Sheet (SIS) and its ice lobes from the Baltic basin, perhaps driven by streaming ice. AMS till fabrics are robust indicators of ice‐flow history and till kinematics, and provide a unique tool to investigate till kinematics within and amongst till units. The till section investigated here contains ~8 m of the Dalby Till – a dark grey silt‐clay rich till deposited during one or more Baltic advance – overlain by ~1.5 m of the regional surface diamicton. AMS fabrics within the lower part of the Dalby Till conform to the regional surface fluting, and reflect sustained flow from the ENE with progressive increases in basal strain. A boulder‐rich horizon approximately 3 m from the base of the till marks a restricted excursion in till fabric direction, fabric strength and style of strain. Ice flow is from the SW and W in the upper section. We interpret these fabrics to record shifting ice flow and bed conditions at the margins of the Young Baltic Advance ice lobe in southern Sweden, prior to a short‐lived re‐advance of the main body of the SIS over mainland Sweden recorded by the surface diamicton.

The Pleistocene ice-sheet dynamics in north-central Poland based on magnetic fabrics of tills and landform analysis

“…The second responsible mineral may be titanomagnetite, which is popular in crystalline rocks included in the studied tills. A third mineral may be maghemite, which Hopkins et al (2016) suggested may account for the marked decrease in magnetization at 200-300°C. Maghemite has been identified in sediments formed in cold environments (Kodama, 1982), including glacial tills (Gentoso et al, 2012).…”

“…An effective tool for measuring the average orientation of fine grains is the anisotropy of magnetic susceptibility (AMS) method, which has been used to determine not only the directions of movement, but also the mechanism of ice-sheet movement, and to reconstruct processes of subglacial till formation. This method of studying tills has been refined across more than six decades of use (e.g., Fuller, 1962; Stupavsky and Gravenor, 1975; Stewart et al, 1988; Hooyer et al, 2008; Thomason and Iverson, 2009; Gentoso et al, 2012; Fleming et al, 2013; Tylmann et al, 2013; Ankerstjerne et al, 2015; Król and Wachecka-Kotkowska, 2015; Hopkins et al 2016; McCracken et al, 2016; Narloch et al, 2021; Teodorski et al, 2021).…”