Introduction to Glacial Geology

Read: Chapters 1 and 2 in Bennett and Glasser

Preliminary questions:

What is the Quaternary? Answered by the Quaternary Research Institute
- Quaternary time table (terrestrial)
What evidence is there of glaciation?
What kinds of deposits are related to glaciation? Why are they important.
Why is it important to study glaciers and their deposits?

The Quaternary Period

The Pliocene-Pleistocene boundary, which marks the beginning of the Quaternary Period has been hotly contested for decades. The Quaternary basically marks the time of extreme Late Cenozoic cooling. However cooling was not gradual and not uniform over the earth and different stratigraphers used a variety of climatic indicators to mark the boundary, such as the first evidence of continental glaciation, the earliest fossils of modern man, or the first penetration of cold water marine fauna into mid latitudes. Its therefore not uncommon to encounter dates ranging from 3 to 1.6 mya for the beginning of the Quaternary. In the 1980's a section of marine sediments in Vrica, southern Italy, was designated the defining stratotype (Plio-Pleistocene Boundary Stratotype ). The section records the Calabrian Stage in the Mediterranean when warm water fauna became extinct and cold water fauna appeared (i.e the cold water formam Globoratalia Calabra). The base of the section, which marks the beginning of the Quaternary, is dated at around 1.8 mya, which closely coresponds(just above) to the top of Oldavai Polarity Event.

Epochs of the Quaternary

Pleistocene: 1.8 mya - 10,000 ya: Period of repeated continental glaciations
Holocene: 10,000 ya to present:

Evidence of glaciation

Direct evidence

Glacial deposits:
- Sediments: erratics, till, glaciofluvial,glaciolacustrine, and glaciomarine deposits
- Features: moraines, drumlins, eskers, etc.
Glacial erosion:
- Removal of pre-Quaternary saprolite
- Features: glacial striations, glacial valleys, cirques, stoss and lee topography, etc.
Changes in snowline altitude as evidenced by abandoned cirques and other features.
Indirect evidence
Changes in flora and fauna:
- palynology: Pollen stratigraphy (Quaternary Palynology, Univ. of AZ)
  - Compare these maps (John Adams and others) of North America dipicting changes in vegetation: Present and 18000 ya
- appearance and dissappearance of cold water species of forams and other creatures
- mass extinctions
Non glacial climatic changes indicating a cooler climate:
- periglacial and pluvial conditions
Changes in relative sea level (isostatic and eustatic)
- Marine terraces (carbonate) record eustatic sea level high stands (interglacials) at 80,000, 105,000 and 120,000
  - Marine terraces in New Zealand (gns)
- Incision of canyons across continental shelves (eustatic lowering of sea level)
- Marine clay deposition in coastal New England and Canada (isostatic depression)
  - Presumpscot Formation in Maine (MGS)
Increased concentrations of ¹⁸Oin marine forams
¹⁸Oin carbonate cave deposits
- Devil' Hole, Nevada (USGS)
Increased detrital marine sedimentation and dropstones (Heinrich Events, NOAA)
Loess deposits
- Wind-Born Dust Holds Clues to Early Climate, 1996, Banerjee and other

Why study glaciers and their deposits?

Importance of glacial deposits

Most surficial deposits in the Northeast and upper Midwest were deposited by glaciers and glacial meltwater.
- In New England where bedrock is crystalline igneous and metamorphic rock, most of the ground water comes from aquifers composed of glacial sediments.
- Glacial sediment are an important resource:
  - Sand and gravel: construction aggregate
    - Sand and gravel mining in North Dakota
    - USGS Construction sand and gravel statistics
  - Clay from glacial lakes: brick
- Land use is greatly influence by glacial deposits which control permeability, arability, etc.
  - Surficial deposits affects the distribution of certain plants.
  - Surficial deposits influence the engineering design of major buildings and structures, provide building aggregate, location of hazardous wastes sites.
In New England the erosion of glacial deposits provides sediment for beaches. Moraine-related outwash on Cape Cod and Long Island is the principle source of beach sand.

Other effect of glaciation

Topography and drainage networks have been modified by glaciation.

More economic reasons to study glaciers

Used in some countries and a source of drinking water and hydroelectric power
Do glaciers affect people? from NSIDC's All about glaciers

Stratigraphy: How do we recognize more than one event?

Note: "Ice Age" is not necessarily synonymous with the Pleistocene--Although the terms are commonly used interchangeably.

Evidence of multiple glaciations in Late Cenozoic: Record of interglacial episodes

Paleosols between overlapping glacial deposits
Glacial terraces in alpine regions: Older terrraces typically lie at higher elevations
Pollen stratigraphy in lakes and bogs beyond the glacial limit. Cooling is characterized by a higher percentage of herb and shrub (nonboreal) pollen. Boreal pollen is primarily birch, spruce and pine. Warm phases are characterized by pollen from broad-leaf/mix-oak forests.
High level marine terraces (e.g. Sangamon ±20 meters above present sea level)
Marine stratigraphy (micropalontology, sedimentation rates, O¹⁸Oxygen isotope (Delphi Project)
Ice cores
- Radiocarbon dating of ice (University Utrecht)
- University of Arizona, Trends in Chemistry Ice Core Lab by Ray Brice
Loess stratigraphy. Depositional rates of wind blown silt are highest during glacial cycles. Interglacial cycles are recorded by the formation of paleosols.
- Wind-born dust holds clues to eary climat e, Banerjee, S.K, and Jackson, M., 1996, EOS v.8, n. 8, p. 12-14.

Current research on glaciers

Study of ice cores
- Importance of ice cores: During this age of apparent climatic warming its imperative that we know and understand past climatic fluctuations. Is the warming experienced in the past decade cause by anthropomorphic-driven changes in the atmosphere or by normal climatic oscillations? Ice cores record changes in temperature, precipitation, ice volumes (¹⁸O), volcanic activity and atmospheric gasses. Moreover the data are datable over several thousand years.
- It's important to understand how glaciers respond to environmental change, particularly that induced by humans.
  Sites to Explore
  - Sea level and Climate,USGS factsheet <http://pubs.usgs.gov/factsheet/fs2-00/>
  - PaleoEnvironment, (Ice Cores) Law Dome, East Antarctica (AAD Antarctica online)
  - An understanding of long-term climate changes, with some surprises, is emerging from analysis of ice core samples, Deborah Schoen, 1999, Environmental Science And Technology, ACS, v 33, Issue 7 pp. 160 A-163 A
  - ** AGU Science form everyone: Climate and global change
    - Deciphering Mysteries of Past Climate From Antarctic Ice Cores [Earth in Space, November 1995)
    - Ice Sheets Play Important Role in Climate Change [Eos. July 4, 1995]
    - Twin Ice Cores From Greenland Reveal History of Climate Change, More [Earth In Space, October 1996]
  - The Last Interglacial, timing and environment s (USGS)

[Glacial and Quaternary Geology] [extended GeoIndex][QkRef][Geological Sciences] [Degree Programs] [Salem State College]
Lindley Hanson (email) Last Modified 1/15/03