312 rocks
pdf
keyboard_arrow_up
School
University of Texas *
*We aren’t endorsed by this school
Course
301
Subject
Geology
Date
Apr 3, 2024
Type
Pages
3
Uploaded by CorporalPelicanMaster1045
Stromatolites
1.
What is the geologic feature?
curved structures with multi-layered interiors
2.
How does the geologic feature form?
formed by trapping sediments and
secreting mucus to bind particles together, layer upon layer of sediments
bound by the organisms and the secretions they produce
3.
Where does the geologic feature form (types of environments)?
hypersaline
lakes and marine lagoons
4.
How does the geologic feature allow you to tell which way is up?
the shape of
the top of the structure tended to be curved so that there was maximum
exposure to the sun
Mudcracks
5.
What is the geologic feature?
sedimentary structures formed as muddy sediment
dries and contracts
6.
How does the geologic feature form?
The top of the bed has the widest distance
between the polygons and the cracks taper downwards into the bed. If later
sediments come and fill in the cracks and are preserved
7.
Where does the geologic feature form (types of environments)?
These cracks
form polygons on the surface of the mud
8.
How does the geologic feature allow you to tell which way is up?
The tip of the
cracks are always oriented downwards, pointing to the bed base or older part of
the formation.
Dropstones
1.
What is the geologic feature?
fragments of rock that have dropped from an
overlying floating ice sheet and sunk into and depressed the layers beneath
them.
2.
How does the geologic feature form?
that has come from the melting glacier
is substantially different in size than the material on the seafloor.
3.
Where does the geologic feature form (types of environments)?
From
icebergs in large bodies of water (ocean) from pieces of glacial ice break off
and float away into whichever body of water the glacier finds at its terminus
4.
How does the geologic feature allow you to tell which way is up?
By seeing
how a dropstone compares to the surrounding sediments, we can tell which
way was originally up. For example, the dropstones shown in the three photos
to the left and below all are oriented stratigraphically up
Tracks and Trails
1.
What is the geologic feature?
the footprints of a tiger, the tail drags of a
crocodile, or pointed depressions from a crab's legs. These impressions often
are filled in with sediment and preserved as
trace fossils
.
2.
How does the geologic feature form?
the footprints of a tiger, the tail drags of
a crocodile, or pointed depressions from a crab's legs. These impressions
often are filled in with sediment and preserved as
trace fossils
. A trace fossil is
an indirect record of an organism having once existed.
3.
Where does the geologic feature form (types of environments)?
Forests,
woods, open land, anywhere where animal marks can be done
4.
How does the geologic feature allow you to tell which way is up?
One
particular type of trace fossil, a footprint, can readily show which way is up by
seeing in which way the bottom of the foot is relative to the top of the foot in
the impression.
Cone in Cone Structures
1.
What is the geologic feature?
cone-shaped forms made of rock that nest
inside a cone cup.
2.
How does the geologic feature form?
they are usually made of rock that is
both calcareous and contains clays, although there have been a few found that
are made of siliceous material
3.
Where does the geologic feature form (types of environments)?
irregular
layers in fine-grained, argillaceous sandstone
4.
How does the geologic feature allow you to tell which way is up?
these cone in
cone structures form with the large, open end of the cone on the top of the
bedding plane and the apex, or pointed end, of the cone pointing downward
Cross Bedding
1.
What is the geologic feature?
layering within a stratum and at an angle to the
main bedding plane. The sedimentary structures which result are roughly
horizontal units composed of inclined layers
2.
How does the geologic feature form?
from running water
3.
Where does the geologic feature form (types of environments)?
any
environment in which a fluid flows over a bed with mobile material.
4.
How does the geologic feature allow you to tell which way is up?
Ripples can
also help to determine flow direction as they tend to have their steepest
surface facing in the direction of the flow
Sole Marks
1.
What is the geologic feature?
preserved when a coarse sand or silt layer
deposits onto mud
2.
How does the geologic feature form?
when a coarse sand or silt layer deposits
onto mud
3.
Where does the geologic feature form (types of environments)?
grooves left
in a bed by things like sticks being dragged along by a current
4.
How does the geologic feature allow you to tell which way is up?
Measuring
the long axis of the flute cast gives the direction of flow, with the tapered end
pointing toward the flow and the steep end up current
Roots
1.
What is the geologic feature?
They are generally cylindrical in structure
2.
How does the geologic feature form?
From their growth
3.
Where does the geologic feature form (types of environments)?
Anywhere
with rich soil
4.
How does the geologic feature allow you to tell which way is up?
They always
grow downwards
Your preview ends here
Eager to read complete document? Join bartleby learn and gain access to the full version
- Access to all documents
- Unlimited textbook solutions
- 24/7 expert homework help