Download presentation
Presentation is loading. Please wait.
Published byMatthew Franklin Modified over 9 years ago
1
Folding of Shale-Sandstone sequence, Kings Canyon, California FOLDS and thrust Which deformation and stresses cause theses structures ?
2
… Compression …Shortening
3
The fold is like a Thrust defined by its orientation Parts of a fold: –axial plane – limbs –“hinge” Hinge
4
Types of Folds Anticline = arch Syncline = trough Monocline = stair step Dome or Basin Chevron Fold, Laurel Mt., CA
5
Syncline syncline, Israel Youngest rocks in middle
6
Anticline Virgin anticline, southern Utah Oldest rocks in middle
7
Domes & Basins Think of an Egg Carton! Chernicoff and Whitney
8
Grenville Dome: Sinclair, WY Map from Topozone.com
9
Syncline- Anticline Pairs + Domes: Zagros Mts, Iran NASA “Earth as Art” web page
10
Monocline
11
Fold Classification
12
Fold in Glacier, Antarctica
13
Folds axis are perpendicular to the main direction of compression
14
Little Shuteye, Sierra Nevada, CA David Rogers Casey Moore, UCSC Domes are not produced by horizontal but vertical compression
15
Minor Folds and Foliation Are Clues to Much Larger Structures
16
Foliation Pressure –pressure flattens and/or aligns minerals in a rock –platy or sheet-like structure reflects the direction in which pressure was applied –Slate, schist, and gneiss foliated Microscope Image of Foliated Garnet Schist, VT 1 mm
17
Foliation In every case, the foliation is: In the direction of least resistance at right angles to the direction of greatest compression.
18
Fold And Foliation
19
Folds and Foliation
20
How Geologists Use These Clues Here's an outcrop that might be seen in the field.
21
Minor Folds and foliations can be used to determine the axe of the fold
22
Pay attention it migth look like folds K = Cretaceous J = Jurassic Tr = triassic At X, we have younger rocks surrounded by older rock
23
But it is produced by differential errosion on a thrust Dark green is older rock, thrust over the younger yellow rock The Klippe (K) W is a Fenster or Window
24
Folds and and Thrust are often associated The overturned fold in the upper diagram may break, yielding an overthrust fold or thrust fault
25
Folds and thrust have the same origin
26
Small thrust fault, Las Vegas, NV, Source: M. Miller, U. of Oregon Reverse Fault
27
Thrust Faults in Snow
28
fold-thrust complex developed in Upper Jurassic limestones in the Haut Giffre area of the Subalpine thrust belt (Morcles nappe in France) R.W.H. Butler Folds and thrust are both responsible for the orogens
29
Folded Appalachians Near Harrisburg, PA, Source: NASA
31
Folding in Malaspina Glacier, AK, 1969
32
Oil and Gas Concentrate in Domes Chernicoff and Whitney
33
Growth of Minerals
34
Bohlen et al., 1987 Folded Amphibolite in Marble, Warrensburg (K. Hollocher, NYSGA field photo) Small Scale Structures Mimic Large Scale Structures!!
35
Mulwaree fault zone, Australia, Tullis et al. Foliated Gneiss, Nunavut, S. Tella Photo. Foliated Slate, Shelburne, VT, UVM Foliation Macroscopic and Microscopic Feldspar (strong) Quartz (weak) Mulwaree fault zone, Australia
36
Pressure K. Hamblin A. Kronenberg Cararra Marble Deformation Experiments BrittleDuctile
37
Continental Extension Chernicoff and Whitney
38
Nevada Bureau of Mines and Geology Basin and Range
39
Extension – Crust Thins Ductile – Faulting Brittle
40
Shearing –lateral slip creates faults –common at transform boundaries
41
Faults –result from brittle deformation –rocks offset across fault –Sides referred to as “hanging wall” and “footwall” –3 types of fault Hanging Wall Footwall
42
Strike & Dip –Describe fault orientation –Direction of slip determines kind of fault: “dip-slip” or “strike-slip” Chernicoff and Whitney
43
Normal Fault, Lamb Canyon, CA Normal Fault
44
Strike-slip fault near Las Vegas, NV, Source: M. Miller, U. of Oregon Strike-Slip Fault
45
Strike-slip fault displacement in orchard
46
Joints Brittle “cracks” in rocks Form near surface Regular spatial distribution No offset
47
Calcite veins in joints of marble, Laurel Mt., CA Preferential weathering of joints in Sandstone;
Similar presentations
© 2025 SlidePlayer.com. Inc.
All rights reserved.