LATE WISCONSINAN GLACIATION OF SOUTHERN NEW ENGLAND: TIMING AND - - PowerPoint PPT Presentation

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LATE WISCONSINAN GLACIATION OF SOUTHERN NEW ENGLAND: TIMING AND DEPOSITS Bryan A. Oakley Department of Environmental Earth Science Eastern Connecticut State University Willimantic, CT, USA Presentation to the Wood-Pawcatuck Watershed

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LATE WISCONSINAN GLACIATION OF SOUTHERN NEW ENGLAND: TIMING AND DEPOSITS

Bryan A. Oakley

Department of Environmental Earth Science Eastern Connecticut State University Willimantic, CT, USA Presentation to the Wood-Pawcatuck Watershed Association 27 June 2016

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Timing - Terminology

QUATERNARY PERIOD - Last 2.54 million years of geologic time PLEISTOCENE EPOCH – All of Quaternary Period except last 11,500 years WISCONSINAN STAGE – Last glacial age of the Pleistocene (70,000 yBP to 11,500 yBP). HOLOCENE STAGE – Last 11,500 years

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The Laurentide Ice Sheet

http://www.cosmographicresearch.org/prelim_glacial_maximum.htm

SLIDE 4

www.sflorg.com/

WHY DO WE CARE ABOUT A 20,000 YEAR OLD ICE SHEET ANYWAYS?

http://ice.nasa.gov/images/Jakobshavn_retreat-1851-2006-590.jpg

Jakobshavn Glacier (Greenland)

SLIDE 5

Braithwaite, 2002

Greenland Outlet Glaciers:

A key to understanding future sea level rise

Zwally et al., 2002

SLIDE 6

Rahmstorf et al., 2012

Sea level rise 1975 - 2012: About half from Greenland

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26,000 yBP 16,000 yBP

After Dyke and Prest, 1987 and Dyke et al., 2002

32,000-35,000 yBP Duration and extent of the Laurentide Ice Sheet:

S. New England

SLIDE 8

Stone and Sirkin, 1996

ICE FLOW DIRECTIONS

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SLIDE 10

Laurentide Thickness: ICE-5G

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Oakley and Boothroyd, 2012 Quaternary Research

What do I think…? “Thin Ice” in S. NE ~ 1,000 ft thick or so in W-P watershed

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RELATIVE SEA LEVEL Block Island

Oakley and Boothroyd, 2012

Eustatic Curve:

Peltier and Fairbanks (2008)

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Laurentide was at the ‘LGM’ by ~26,000 yBP

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Oakley, 2012 Ice margins modified from: Dyke and Prest, 1987 Ridge, 2010; Goss, 1993 Smith, 2010 Charlestown Moraine

Glacial Lakes in Rhode Island and Block Island Sounds, 21,000 yBP

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Charlestown Moraine
Tectonic recessional end moraine representing a

significant still-stand/readvance of the LIS

21,000-ish yBP
Wolf Rocks/Congdon Hill 20,300/20,200-uish yBP

Wood-Pawcatuck Watershed was “Ice Free” by ~20,000 yBP

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Miles

30 Kilometers 20 15 10 5 10 5

Stratified Material End Moraine - Till and Stratified Material

EXPLANATION

Till

QUATERNARY DEPOSITS OF RHODE ISLAND

Thick Stratified Deposits Granitic Till Upland Compact Till Upland Block Island Complex Narragansett structural basin

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Stratified deposits….

Sediment deposited by meltwater
Glacial lakes dominated the landscape…

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SLIDE 19

Quaternary Geology of the Carolina – Quonochontaug Quads

Stratified Deposits Till

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Braided River on a Delta Plain

J.C. Boothroyd

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“C. Pebbly Sand Fluvial Facies” – i.e. Braided River deposits

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“C. Pebbly Sand Fluvial Facies” – i.e. Braided River deposits

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Morphosequence

Time-equivalent group of landforms that extend

from the collapsed former ice margin at the proximal end of the deposit

(Koteff and Pessl, 1981; Stone and Stone, 2005)

SLIDE 24

Modified from Stone and Stone, 2005

MORPHOSEQUENCE CHARACTERISTICS

Ice

Stratified Deposits Base Level Control

Which is all complicated by isostatic rebound….

SLIDE 25

After Koteff and Pessl, 1981

1 = Oldest 4 = Youngest

Ice Retreat

Ice Margins

Morphosequence 1 Deposited first and is the oldest Collapsed areas “Heads of Outwash”

Morphoseq. 2
Morphoseq. 3

Morphosequence 4 Is the youngest

ICE

SLIDE 26

http://pubs.usgs.gov/sir/2014/5216/pdf/sir2014-5216.pdf

Geologic Cross-Section:

Congdon Hill to Worden Pond

Worden Pond

Deltaic Morphosequences

North South Congdon Hill

SLIDE 27

SLIDE 28

LATE WISCONSINAN GLACIATION OF SOUTHERN NEW ENGLAND: TIMING AND DEPOSITS

Bryan A. Oakley

Timing - Terminology

QUATERNARY PERIOD - Last 2.54 million years of geologic time PLEISTOCENE EPOCH – All of Quaternary Period except last 11,500 years WISCONSINAN STAGE – Last glacial age of the Pleistocene (70,000 yBP to 11,500 yBP). HOLOCENE STAGE – Last 11,500 years

The Laurentide Ice Sheet

WHY DO WE CARE ABOUT A 20,000 YEAR OLD ICE SHEET ANYWAYS?

Greenland Outlet Glaciers:

A key to understanding future sea level rise

Sea level rise 1975 - 2012: About half from Greenland

26,000 yBP 16,000 yBP

32,000-35,000 yBP Duration and extent of the Laurentide Ice Sheet:

ICE FLOW DIRECTIONS

Laurentide Thickness: ICE-5G

What do I think…? “Thin Ice” in S. NE ~ 1,000 ft thick or so in W-P watershed

Eustatic Curve:

Peltier and Fairbanks (2008)

Laurentide was at the ‘LGM’ by ~26,000 yBP

Glacial Lakes in Rhode Island and Block Island Sounds, 21,000 yBP

significant still-stand/readvance of the LIS

Wood-Pawcatuck Watershed was “Ice Free” by ~20,000 yBP

QUATERNARY DEPOSITS OF RHODE ISLAND

Stratified deposits….

Stratified Deposits Till

“C. Pebbly Sand Fluvial Facies” – i.e. Braided River deposits

“C. Pebbly Sand Fluvial Facies” – i.e. Braided River deposits

Morphosequence

from the collapsed former ice margin at the proximal end of the deposit

MORPHOSEQUENCE CHARACTERISTICS

Ice

Which is all complicated by isostatic rebound….

1 = Oldest 4 = Youngest

Ice Retreat

Ice Margins

ICE

Geologic Cross-Section:

Congdon Hill to Worden Pond

Worden Pond

North South Congdon Hill

http://geothermal.isgs.illinois.edu/aasggeothermal/rigs/map/