Field Trip

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Field Trip 3 Paleozoic Rocks II
Cretaceous Stratigraphy of Central Texas
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(No Transcript)
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Field Trip 3 Paleozoic Rocks II

• Location
• Geology
• Assignment / Methods
• Reminders

Text Manual, p. 267-278 Compton, p. 166-171
182-184 242-243.
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Location
Hamilton Creek
Stop 1
(E. McBride)
Stop 2
road cut near Max Starke Dam
(E. McBride)
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Location
Creek near Stop 2
(Luis Garcia)
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(No Transcript)
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Geology
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Geology
Paleozoic Sedimentary Rocks
Pennsylvanian Smithwick Shale Ordovician
Honeycut Formation of Ellenburger Group
Bastrop
N
5 miles
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(Manual, p. 272)
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Geology
Paleozoic Events

• Flooding by Shallow Seas
• Uplift Ouachita Mts (Penn)
• Faulting (Penn)
• Erosion of Ouachitas (P-J)

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Geology
Ellenburger Group

• sabkha
• evaporites
• karst
• natural gas - subsurface

(nps.gov)
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Geology
Guidebook of the Geology of Travis County
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Geology
Smithwick Shale

• marine
• high sediment supply
• turbidites

(E. McBride)
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Field Trip 3 Paleozoic Rocks II

• Location
• Geology
• Assignment / Methods
• Reminders

Text Manual, p. 267-278 Compton, p. 166-171
182-184 242-243.
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Assignment / Methods
1) Smithwick Shale Paleocurrent and Deformation
Features

• measure and plot the orientation of
• 1) joints
• 2) faults
• 3) sandstone dikes
• 4) fossil wood fragments
• 5) current ripples and solemarks

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Assignment / Methods

• water-saturated sediment
• excess pore pressure

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Assignment / Methods
clastic dikes and joints
(E. McBride)
(E. McBride)
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groove casts
Assignment / Methods
flute casts
(416M)
solemarks
(416M)
416M
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Assignment / Methods

• plot features in 4 rings
• show of measurements
• show bi-directional trends

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Assignment / Methods
2) Honeycut Formation Checklist
road cut near Max Starke Dam
(E. McBride)
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Assignment / Methods
limestone vs dolomite
Dolomite - Thin Section
Dolomite - SEM
(Soil Science Society of America)
(Soil Science Society of America)
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Assignment / Methods
stylolites vs stromatolites
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Assignment / Methods
fault breccia vs solution collapse breccia

• solution collapse breccia filled cave
• fault breccia repeated crushing / cementation

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Assignment / Methods
soft-sediment deformation vs brittle
deformation
(Compton, p. 243)

• faults break more resistant layers only
• mottled textures in shear zone

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Assignment / Methods
teepee structure and geopetal structure
Geopetal Thin Section
(Matt Campbell)
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Field Trip 3 Paleozoic Rocks II

• Location
• Geology
• Assignment / Methods
• Reminders

Text Manual, p. 267-278 Compton, p. 166-171
182-184 242-243.
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Reminders

• Water
• Lunch
• Clipboard
• Colored Pencils
• Ruler Protractor
• Extra Paper

• Brunton
• Rock Hammer
• HCl Acid
• Hand Lens
• Field Notebook
• Lab Manual

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Field Trip 3 Paleozoic Rocks II
Cretaceous Stratigraphy of Central Texas
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Cretaceous Stratigraphy of Central Texas

• Paleogeography and Sea Level
• Stratigraphy

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Paleogeography and Sea Level
Late Cretaceous Paleogeography
http//www4.nau.edu/geology/master.html?http//www
4.nau.edu/geology/
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Cretaceous Stratigraphy of Central Texas

• Paleogeography and Sea Level
• Stratigraphy

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(Manual, p. 272)
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Stratigraphy
(Duex and Lock, Univ. LA)

• relatively flat-lying
• retreating escarpment

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Stratigraphy

• resistant and non-resistant limestone

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(www.cretaceousfossils.com)
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Stratigraphy

• hard (pure) and soft (clay-rich)
• shallow subtidal and supratidal

(www.cretaceousfossils.com)
Hensell Sand Badlands

• sand, conglomerate, paleosols
• terrestrial environment

Glen Rose Limestone Stairsteps
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Stratigraphy
Edwards Limestone Swiss Cheese

• pure limestone and dolomite
• chert-rich

Oyster-rich Del Rio Clay

• carbonaceous clay
• pyrite anoxic lagoon