The structure and origin of the Strand Moraines, Antarctica P.J. Currie (BSc Hons).

Abstract:

The Strand Moraines is a stagnant ice-cored moraine. It is a glacial remnant of the last Glaciation (20-5 kyr ago) and is grounded against the Bowers Piedmont Glacier on the west coast of McMurdo Sound, Antarctica.

The surface topography of the Strand Moraines is controlled and related to the structure of the underlying ice. The structure indicates that the Strand Moraines is a homogeneous ice body that has undergone two periods of folding deformation. The mechanism of fold development can be equated with cylindrical folding mechanisms and formed during glacial movement processes.

Oxygen isotope analysis determined that the Strand Moraines ice core is a mixture of alpine glacier ice and seawater derived ice. The seawater is considered to have been incorporated into the original ice body by glacial processes associated with a grounded and thickening ice sheet. The presence of a mirabilite salt bed supports this. Mirabilite is precipitated from freezing seawater.

Englacial and surficial debris present at the Strand Moraines are genetically related. The surficial debris is derived from the englacial page 66 debris by surface ablation. It has a coarser texture because the fine sediments are removed by wind deflation and meltwater winnowing. The debris originated in a subglacial environment and moved to an englacial position by glacial processes.

The debris has a mixed provenance and indicates a continental source for the Strand Moraines.

Evidence from this study suggests that the Strand Moraines was formed 6.8 kyr ago at a time when the grounded ice sheet present in the McMurdo Sound during the last Glaciation was in recession. Ice flow models for the ice sheet have been postulated. It is considered that the ice sheet is as likely to have flowed into the McMurdo Sound from the south in a northward direction as flowed around the northern end of Ross Island and in a southern direction as proposed by earlier authors.