Grain textural analysis across a range of glacial facies

Abstract

ABSTRACT. A technique proposed by Hooke and Iverson (1995) to identify deformed subglacial sediments is reviewed and tested, based on two main objectives. First, an investigation of whether the fractal dimension can distinguish between non-deformed and deformed facies; for which we compare supraglacial and subglacial facies explicitly. Second, an evaluation of whether the fractal dimension can be used as a diagnostic criteria to discriminate between different styles and degrees of basal deformation. This is tested using a range of sediments from the deformation continuum suggested by Hart and Boulton (1991b). Sixteen subglacial samples were selected from Quaternary sites in England and three supraglacial samples from the modern Haut Glacier d'Arolla, Switzerland. The mean fractal dimension for the subglacial diamicton matrix facies was 2.92, similar to findings of 2.90 by Hooke and Iverson (1995) for their basal tills. The supraglacial facies displayed a mean fractal dimension of 2.83, which is unusually high for facies which are assumed to be undeformed. A Mann^Whitney U test showed that fractal dimensions of supraglacial and subglacial diamicton matrix facies were not significantly different. No significant difference was found between the fractal dimensions of the different tectonic facies within the subglacial group. It may be impossible to separate the subglacial and supraglacial facies because of complex debris paths within the glacier. Grain fracture or parent lithology may affect the particle-size distribution of subglacial facies.

Textural and Geochemical Characteristics of Proglacial Sediments: A Case Study in the Foreland of the Nelson Ice Cap, Antarctica

“…The above mean fractal dimensions are very close to 2.90, reported by Hooke and Iverson (1995) and Khatwa et al (1999) for deformed glacial sediments, 1 that these redeposited sediments in the periglacial foreland have inherited the signal of grain size distributions from the glacial tills. The above mean fractal dimensions are very close to 2.90, reported by Hooke and Iverson (1995) and Khatwa et al (1999) for deformed glacial sediments, 1 that these redeposited sediments in the periglacial foreland have inherited the signal of grain size distributions from the glacial tills.…”

The origin and significance of debris‐charged ridges at the surface of storglaciären, northern sweden

“…(1987). For comparison, Hooke and Iverson (1995) Khatwa et al . (1999) stress that parent material will have a profound effect on the particle-size distribution characteristics of a given subglacial till facies.…”

“…For comparison, Hooke and Iverson (1995) calculated a mean slope of -2.90 from 11 samples of 'deformed basal sediment' obtained from boreholes on Storglaciären. Khatwa et al . (1999) calculated a mean fractal dimension of -2.92 for a range of interpreted subglacial diamicton facies from British Quaternary lowland sites, and compared the results to 'passively transported' supraglacial debris from Haut Glacier d'Arolla, Switzerland.…”

“…(1999) calculated a mean fractal dimension of -2.92 for a range of interpreted subglacial diamicton facies from British Quaternary lowland sites, and compared the results to 'passively transported' supraglacial debris from Haut Glacier d'Arolla, Switzerland. Khatwa et al . (1999) stress that parent material will have a profound effect on the particle-size distribution characteristics of a given subglacial till facies.…”

Drainage through subglacial water sheets

“…Measurements on tills generally show that a $ 2.9 [Hooke and Iverson, 1995;Khatwa et al, 1999] but can be lower [e.g., Fischer and Hubbard, 1999]. Here we assume that the fractal index a = 3, which indicates that all measured grain sizes occupy roughly the same volume of the till.…”