Transcript Mudstone with clasts

Cool Cores Capture Climate
Change
Goals & Objectives
To determine the effect of Earth's temperature changes, and
glaciers' respective movements, on ice core sediments.
-- How can one 'read' an ice core?
-- What sediments are present in warm or cool climates and
why are they present?
-- How does one use the ANDRILL coring program?
-- What does our data tell us?
ANDRILL
•
•
•
ANDRILL (ANtarctic geological DRILLing) is a multinational collaboration comprised of
more than 200 scientists, students, and educators from five nations (Germany, Italy,
New Zealand, the United Kingdom and the United States) to recover stratigraphic records
from the Antarctic margin using Cape Roberts Project (CRP) technology.
The chief objective is to drill back in time to recover a history of paleoenvironmental
changes that will guide our understanding of how fast, how large, and how frequent were
glacial and interglacial changes in the Antarctica region.
Specific science objectives of :
o obtain high-resolution sediment cores that record major glacial events and
transitional periods over the past 40 million years;
o determine orbital and sub-orbital glacio-climatic fluctuations that vary on 100,000,
40,000, and 20,000 year cycles
o obtain a refined record of the onset and development of the East Antarctic ice sheet
(EAIS) 40 million years ago
o identify how the Antarctic region responded to past events of global warmth
o derive a detailed history of Antarctic Holocene environmental change at the end of
the last glaciation
o test global linkages between climate changes in the Northern and Southern
hemispheres
Sediment Cores
•Our study of past climate (paleoclimate) takes place in the Southern Ocean region,
around the continent of Antarctica.
•In warm climatic periods, the ice surrounding Antarctica retreats.
•When this occurs the ocean is exposed to increased sunlight and air. These conditions
favor an abundance of marine plant and animal life, including diatoms. Conversely, during
cold periods, the ocean also cools; consequently sea ice increases and covers the ocean
surface.
• When sea ice covers the ocean surface, exposure to sunlight and air is reduced in the
ocean below. During these times, different, and fewer, species of organisms thrive. •When
ocean organisms such as diatoms die their un-decomposed silicified (carbon rich) body
parts, sink to the ocean floor and become layers in the sediment. Thus, this change in life
conditions is recorded in the composition of the sediment cores.
Mudstone
with clasts
Mudstone embedded with small rocks (clasts) indicates that
an ice shelf covers the ocean. Glaciers pick up stones as
they move across the land and become an ice shelf over the
water. When the underside of the shelf melts it releases
rocks and mud that settle to the sea floor. Since the ocean
has been under the ice shelf away from sunlight for a long
time, there will be few diatoms in this layer. Where in the
picture will this layer be created?
Sediment rate = slow
Card #1
Diamictite
Diamictite is composed of coarse, angular and well-rounded
clasts (rocks) of many types, embedded in a mixture of mud.
It is described as poorly sorted. Diamictite is created in
subglacial environments, meaning that it is deposited under
the ice sheet where the ice meets the land. The clasts and
sand grains may show evidence of breakage and rolling.
Where in the picture will this layer be created?
Sediment rate = fast
Card #2
Diatomite
Diatomite is composed of the remains of diatoms,
whose silica shells (SiO2) make up the layers of this
sediment. Diatoms are single celled algae found all
over the world in hundreds of species and varieties.
Diatom species are temperature sensitive, so their
presence is a clue to past ocean temperatures. Where
diatomite is deposited, the ocean is open to the
atmosphere and sunlight (not covered by sea ice) so
#3 will
these organisms can thrive. Where inCard
the picture
this layer be created?
Conglomerate
Conglomerate layers are made of unsorted rocks
(clasts) larger than sand, and as big as pebbles, that
are cemented together in a matrix of finer grains of
material. These rocks are carried along with the
glacier as it advances and are generally rounded in
shape. Where in the picture above would you expect
to find this layer being created?
Card #6
Using PSICAT
• fr
Ice Shelf Animation
• http://andrill.org/system/files/web/images/edu/iceshelfadvanceretreat.swf
At +5 degrees, the ice shelf is completely gone. The water is exposed to sunlight
and life, including diatoms, flourish. The green sediment (containing diatomite)
is deposited. At -2 degrees, the ice shelf advances conglomerate is deposited
and then once the ice shelf is really thick, mudstone with clasts is deposited
underneath the ice shelf.
Animation Core
Diagram
• 1 m = 1000 years
• first symbol is for diatoms
• second symbol is for clasts
Ice Core
How To Read an Ice Core
Diatomite - open ocean and warm temperatures
Sandstone - sand-like rocks brought by the wind and water
and cemented by pressure
Diamictite - point where ice meets land, but is not exposed to
sunlight yet
How to Read an Ice Core
Slide 1: Ice shelf grows and contracts, as the diamictite and
diatomite layers alternate. The earth undergoes periods of
mild warming and cooling.
Slide 2: The earth becomes warmer. The ocean is exposed to
sunlight and diatoms (algae) flourish.
Climate Change
•Over the course of Earth’s history, the climate has changed dramatically, and
has shifted between warm and cold phases.
•For example: Antarctica and Arizona, places that were once sprawling with
lush vegetation because of the warm climate, are now dry deserts
•Climate change today, however, has much farther reaching effects,
including: causing us to change the location of crops grown in specific areas,
making the areas that people now thrive in possibly uninhabitable, and
changing or eliminating current animal habitats.
•By analyzing sediment cores, scientists can observe and analyze changes in
Earth’s climate.
How Sediment Cores Capture
Changes in Life Conditions
•In the Southern Ocean region, around the continent of Antarctica, warm
climate causes ice surrounding the continent to retreat.
•As the newly uncovered ocean gets exposed to sunlight and air, marine plant
and animal life, including diatoms, flourish
•However, as the ocean cools during colder periods, the sea ice refreezes and
covers the ocean surface that was exposed to sunlight and air, thus causing
fewer organisms to survive
•However, as the ocean organisms die, they sink to the ocean floor; leaving
their un-decomposed silicified (carbon rich) body parts to become layers in
the sediment, thus leaving a recording of a change in life conditions in the
sediment.
How Sediment Cores Capture
Changes in Glacier Activity
•Ice shelves are formed when accumulations of ice and snow over thousands
of years form glaciers that flow off the land and into the ocean.
•During cold periods, ice shelves advance until they are grounded on the
ocean floor.
•This causes them to mix the sediment layers and compact the remaining
materials with their weight.
•During warm periods, retreating grounded ice shelves leave marks in thick
deposits of small rocks, called clasts and form smooth surfaces on which new
layers start to accumulate.
•In this way, sediment layers record periods of climate change.
How is the data stored in the cores decoded and
analyzed?
• Specially equipped research ships use a coring apparatus to bring
samples of these sediment layers to the surface as sediment cores.
Once these cores are recovered, scientists are able to analyze them
and uncover the story of past climates.
• Unlike tree rings that contain a relatively short record of climate
history, sediment cores—which preserve hundreds of thousands of
years of Earth's history—tell a much longer story.
• Sediment bands (seen as changes in color, texture and composition
in the core) indicate climate cycles that each may span hundreds to
thousands of years.
• The record in these cores helps researchers piece together Earth's
history of climate change.