Determining rotational direction of rotation structures using prolate shaped grains within till

Micromorphology is used to analyze a wide range of sediments. Many microstructures have, as yet, not been analyzed. Rotation structures are the least understood of microstructures: their origin and development forms the basis of this thesis. Direction of rotational movement helps understand formative deformational and depositional processes. Twenty-eight rotation structures were analyzed through two methods of data extraction: (a) angle of grain rotation measured from Nikon NIS software, and (b) visual analyses of grain orientation, neighbouring grainstacks, lineations, and obstructions. Data indicates antithetic rotation is promoted by lubrication, accounting for 79% of counter-clockwise rotation structures while 21 % had clockwise rotation. Rotation structures are formed due to velocity gradients in sediment. Subglacial sediments are sheared due to overlying ice mass stresses. The grains in the sediment are differentially deformed. Research suggests rotation structures are formed under ductile conditions under low shear, low water content, and grain numbers inducing grain-to-grain interaction.

HG 276.80-276.95 Thin Section

Coarse grained sample, with grains ranging from small to large in size. Shapes range from angular to rounded. This sample is abundant in lineations, and rotation structures can also be seen around larger aggregates. Many large grains are fractured and minor grain stacking can also be seen.

HG 35.0-35.10

Brown sediment with clasts that range from small to medium in size. The grain shape ranges from angular to sub-rounded. Lineations and rotation structures were the most common throughout the sample. Grain crushing/stacking and a few comet structures were also present. Clay material was also dispersed throughout the sample.

HG 114.60-114.70

Brown sediment with clasts ranging from small to medium in size. Clast shape ranges from angular to sub-rounded. Lineations and rotation structures are common throughout this sample. Some comet structures and grain crushing can also be seen throughout in minor amounts.

HG 129.15-129.30

Brown sediment with clasts ranging from small to medium in size. Clast shape ranges from angular to sub-rounded in shape. Lineations and rotation structures can be seen throughout the sample. Some comet structures and grain stacking can also be seen.

HG 129.50-129.60

Brown sediment with multiple domains. There are two finer grained domains that contain a few small clasts. These two can be distinguished based on the abundance of clay material(darker brown). The coarse grained sediment contains clasts ranging from small to medium in size, and angular to sub-rounded in shape. This domain contains lineations, rotation structures, comet structures, and some edge-to-edge grain crushing.

HG 176.10-176.20

Dark brown sediment with clasts ranging from small to large in size. Clast shape ranges from angular to sub-rounded. Lineations and rotation structures can commonly be seen throughout the sample. Comet structures, grain crushing, and fractured grains can also be seen in minor amounts.

ARTh 1A

Dark brown sediment with clasts ranging from small to large in size. The clast shape ranges from angular to sub-rounded. Lineations and rotation structures are common throughout the sample. Some comet structures and grain crushing can also be seen.

ARTh 1B

Brown sediment with clasts ranging from small to large. The clast shape ranges from angular to sub-rounded. Lineations and rotation structures are commonly seen throughout this sample. Edge-to-edge grain crushing and comet structures can also be seen in minor amounts.

MB-x-2

Dark brown sediment with clasts ranging from small to large in size. The clast shape ranges from angular to sub-rounded. Clasts appear fractured, weathered, and are well dispersed. Lineations and rotation structures are commonly seen throughout the sample. A few comet structures and grain stacks can also be seen.

J.R. Ai-6

Coarse grained sediment with clasts ranging from small to large. Clast shape ranges from angular to rounded. Lineations are abundant throughout the sample, along with rotation structures. Some comet structures and grain crushing can also be seen throughout the sample. Rotation structures can mainly be seen around larger clasts.

11 PTA002.2

Dark brown sediment with clasts ranging from small to large in size. Clast shape ranges from angular to rounded. Lineations and rotation structures are abundant in this sample. Grain crushing can be commonly be seen throughout. Grain stacking and comet structures are present in minor amounts.

11 PTA008

Greyish-brown sediment with clasts ranging from small to large in size. Grain shape ranges from angular to rounded in shape. Many grains appear to be fractured or weathered. Lineations and rotation structures are abundant within this sample. Grain crushing and stacking can also be seen in this sample. Comet structures are also present in minor amounts.

Mo03

Greyish brown sediment with clasts ranging from small to medium in size. The clast shape ranges from sub-angular to rounded. Lineations and rotation structures are common throughout the sample. Comet structures can also be seen. Grain crushing and stacking are also present throughout the sample.

RRC-1

Brown sediment with clasts ranging from small to large in size. Clast shape ranges from angular to sub-rounded. Lineations and rotation structures can be commonly seen throughout the sample. Minor amounts of comet structures, grain crushing and grain stacking can also be seen.