Glacial Deposit

GLACIAL DEPOSIT

Sediments and rock materials that are transported and laid down by glaciers or glacier-related processes (ice, meltwater, wind, or icebergs). They form when glaciers erode bedrock, carry debris, and then deposit it as the ice melts or retreats.

Types of Glacial Deposits

-Glaciofluvial Deposits

-Glaciolacustrine Deposits

-Glaciomarine Deposits

FORMATION PROCESS of Glacial Deposits

1.Erosion

2.Transport

3.Deposition

Plucking

– ice freezes onto rock fragments and pulls them away

Abrasion

– embedded rock fragments scrape and grind the bedrock

Supraglacial

– on top of the ice

Englacial

– within the ice

Subglacial

– dragged along the base

GLACIOFLUVIAL deposits

are stratified (layered) and sorted sediments primarily sand, gravel, and silt that were transported and deposited by flowing meltwater from a glacier.

The term glaciofluvial is formed by combining two Latin-based roots to describe both the source of the material and the agent that moved it

Glacio; derived from the Latin glacies, meaning ice. This refers to the origin of the sediment—it was originally trapped within or eroded by a glacier. Fluvial; derived from the Latin fluvius, meaning river. In geology, "fluvial" refers to any process or landform produced by the action of flowing water.

1. Glacial Melting

2. Meltwater Flows

3. Sediment Entrainment

4. Velocity Drop

5. Deposition & Sorting Repeated

6. Deposit Formation

Formation of GLACIOFLUVIAL deposits

ESKERS

are ridges made of sands and gravels, deposited by glacial meltwater flowing through tunnels within and underneath glaciers, or through meltwater channels on top of glaciers.

KAME

an irregularly shaped hill or mound composed of sand, gravel and till that accumulates in a depression on a retreating glacier, and is then deposited on the land surface with further melting of the glacier.

OUTWASH

deposit of sand and gravel carried by running water from the melting ice of a glacier and laid down in stratified deposits beyond the ice margin. An outwash may attain a thickness of 100 m (328 feet) at the edge of a glacier, although the thickness is usually much less; it may also extend many kilometres in length.

VALUABLE MINERALS/AGGREGATES in GLACIOFLUVIAL deposits

-Sand&Gravel

-Gold(Au)

-Magnetite(Fe3O4)

GLACIOLACUSTRINE DEPOSITS

are defined as sedimentary accumulations formed in glacial lake environments, characterized by processes such as suspension sedimentation, iceberg rafting, and subaqueous debris flows, which result in features like rhythmites, and dropstones. These deposits reflect the dynamic interactions between glacial and lacustrine systems.

From Latin 'lacus' (lake) — the lake equivalent of glaciofluvial deposits

GLACIOLACUSTRINE

Varve

is a pair of thin, annual sediment layers (couplets) deposited in glacier-fed lakes, representing one year of accumulation

Varve Light Layer (Summer)

- coarser silt deposit when meltwater is active

Varve Dark Layer (Winter)

- fine clay settling slowly under frozen lake surface

Thick varves

often represent warmer summers (high melt), while thin varves indicate cooler years.

1. Glacial Lake Formation

2. Meltwater Input

3. Suspension Settling

4. Summer Layer (Light)

5. Winter Layer (Dark)

6. Varve Formation

FORMATION PROCESS of Glaciolacustrine

CHARACTERISTICS of Glaciolacustrine

-GRAIN SIZE Very fine-grained: mostly silt and clay

-SORTING Very well sorted due to settling in still water

-TEXTURE Thinly laminated - varved texture. Smooth, fine, & compact

-COLOR Often alternating light and dark layers

KEY LOCATIONS of Glaciolacustrine

Nanaimo, British Columbia (Canada) Lake District (Finland) Lake Agassiz (Canada)

Glaciomarine Deposits

refers to sediment accumulations formed in marine environments where a glacier terminates in water, including materials deposited by meltwater, icebergs, and ice-rafted debris, shaped by tidal and current processes.

Glaciomarine Deposits comes from the word

comes from the word “Glacio” which means ice or glacier, and “Marine” which means of the sea or ocean.

FORMATION PROCESS of glaciomarine

1. Glacier Reaches the Sea

2. Meltwater Plumes

3. Calving & Iceberg Formation

4. Iceberg Drift & Melt

5. Seafloor Accumulation

6. Reworking by Ocean Processes

ICE-PROXIMAL GLACIOMARINE DEPOSITS

Sediments deposited within a few kilometers of the glacier or ice shelf terminus, where glacial processes dominate over marine ones

ICE-PROXIMAL GLACIOMARINE DEPOSITS

-Sorting Very poor. Boulders to clay are all mixed together (diamicton)

Grain Size Coarse — gravel, sand, and till dominate

-Rate Very high — rapid dumping of subglacial material

ICE-DISTAL GLACIOMARINE DEPOSITS

-Sorting Moderate to good — waves and currents organise particles by size

-Grain Size Fine — silt and clay, with rare dropstones from drifting icebergs

-Rate Low to moderate — slow, steady particle settling

ICE-DISTAL GLACIOMARINE DEPOSITS

Sediments deposited far from the glacier, where marine processes (currents, waves, settling) take over from glacial input.

Ice-Rafted Debris

-This is the broader category of all material transported by floating ice and deposited on the seafloor when that ice melts.

-All material carried and dropped by icebergs

Dropstones

-are one part of IRD, but IRD also includes sand, gravel, and fine particles released gradually as the iceberg drifts and deteriorates.

Dropstones

-are one of the most important and visually striking features of glaciomarine deposits. A large rock clast (pebble to boulder) embedded in fine-grained marine sediment

-The large individual clasts within IRD

TILL

-Unsorted, unstratified sediment deposited directly by glacial ice — not by water or wind. It is the raw debris scraped off bedrock and carried under or within the glacier, then dumped when the ice melts or stalls

-Deposited by ice on land or seafloor

CHARACTERISTICS of GLACIOMARINE DEPOSITS

-GRAIN SIZE Coarse near the glacier (ice-proximal), finer farther away (ice-distal)

-SORTING Mix of boulders, pebbles, silt and clay all together. Poorly sorted

-LAYERS Well-stratified. Clearly visible layers (strata)

-FOSSILS Contains marine fossils. Shell fragments, forams, diatoms from saltwater organisms

KEY LOCATIONS of GLACIOMARINE DEPOSITS

Antarctica West & East Greenland fjords, Greenland Svalbard (Norway) Bearing Glacier, Alaska (USA)

RHYTHMITES

Repeated alternating layers of coarse and fine sediment — similar to varves but not strictly annual. They form from any repeated pulse of meltwater input regardless of time interval.

DROPSTONE

Isolated rock fragments — pebbles to boulders — dropped from floating ice into the lake as glacial icebergs drift and melt. The rock sinks and lands on fine lake sediment below. Key identifying feature: Sediment layers beneath the stone are pushed downward by the impact while layers above drape over the stone — this deformation pattern is proof it was dropped from above, not carried by water.