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GLACIAL DEBRIS TRANSPORT & DEPOSITION

photo: boat; Tasman Glacier & supraglacial debrisA. Introduction

Till: sediment deposited by ice (diamicton)

Moraines: accumulations of till

Till characteristics affected by:

Learning outcomes - You should be able to:

Readings


photo: supraglacial debrisB. Debris Sources

Alpine glaciers

All glaciers


C. Supraglacial Debris

High Level Debris Transport

Angular, coarse clasts unaltered by transport Link: angular clastsLink: supra-glacial debris image

Photo: boulder falling off Tasman Glacier, New Zealand Photo: boulder falling off Tasman Glacier, New Zealand Photo: boulder falling off Tasman Glacier, New Zealand

Supraglacial till (melt-out or ablation till)

Image credit: ©Bruce Molnia, Terra Photographics. Image source: Earth Science World Image Bank http://www.earthscienceworld.org/images

Moraines


D. Basal Debris

photo: Tasman glacier englacial debrisLow level debris transport

Basal debris: highly altered by transport

Subglacial till


E. Distinguishing Tills in the Field

Internal sedimentary properties

External relationships


F. Lithostratigraphic units

Formations

Members

Law of superposition

  • younger units overlie older units

  • younger units truncate older beds

  • younger units are behind older units

Picture (400x145, 5.3Kb)

Age limiting estimates

  • maximum age limit: event (unit) must be younger than the dated material

    • outwash must be younger than the stump

  • minimum age limit: event (unit) must be older than the dated material

    • moraine must be older than the tree

Picture (400x308, 22.4Kb)

G. Summary

Debris transport

Deposition and associated tills

Lithostratographic units


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©Karen A. Lemke: klemke@uwsp.edu
Last revised April 14, 2015