Blue Ridge Breakout Session
At the DGMR Blue Ridge / Valley & Ridge Symposium the other week, we had a productive hour-long brainstorming session about unresolved issues in the geology of those two physiographic provinces.
I only attended the Blue Ridge session, and with the blessing of the conference organizers, I'd like to share the results of our ruminations here:
Unresolved issues in Blue Ridge Geology
General Outcomes:
Participants would like to see this as a start to a new state geologic map for 2015.
Participants would like have follow-up workshops to discuss these issues in detail.
Participants would like to develop research needs proposals on these key topics.
Specific Issues:
1. Ramp separating the Cambro-Ordovician carbonates from the rock of the Blue Ridge
a. What is its position?
b. Is it "thick" skinned?
c. Can field work (alone) resolve this?
d. What is its age?
How might this question be resolved?
A. Detailed geologic mapping at 1:24,000 scale across the Blue Ridge / Valley and Ridge transition
B. Applying geophysical techniques such as
a. Seismic reflection
b. Gravity studies
c. Reprocessing old data and reassessing old interpretations
C. LIDAR
2. Working out the problems with the Blue Ridge nomenclature and unit and fault correlations
a. Issues with variability in terminology and correlations across Virginia and between Virginia and North Carolina.
b. Map distribution of faults along the Blue Ridge - need to correlate their timing and extent
How might this question be resolved?
A. Detailed geologic mapping at 1:24,000 scale along the Blue Ridge (N/S) and across the Blue Ridge (E/W).
B. Models for the Blue Ridge need to be presented, discussed and synthesized.
C. Developing a basement "tool kit" for Late Proterozoic rocks: Since we can't afford to date every rock, there is a need for key characteristics for each unit to be agreed upon and applied in the field.
D. Expunge archaic terms and agree upon an appropriate vocabulary.
E. Regular focus group meetings and field meetings are necessary to resolve these issues.
3. When did the Blue Ridge develop its topographic relief?
a. Timing?
b. Is it in a steady state?
c. What is the history of the various erosional surfaces throughout the BR's evolution?
d. How does this correlate with the other physiographic provinces?
How might this question be resolved?
A. Detailed geologic mapping at 1:24,000.
B. Utilize low temperature chronometers such as U/Th/He at a sufficiently detailed spatial scale.
4. Role of the Mesozoic system in the Blue Ridge story and geometry.
How might this question be resolved?
A. Detailed geologic mapping at 1:24,000.
B. Need more geophysical studies.
C. Examine the effects/association of these fractures with water
D. Examine the relationship between features and mineral resource deposits
E. More detailed fracture studies are needed
F. Compare and contrast the Mesozoic rifting with previous rifting cycles
G. A seismic risk assessment needs to be done.
5. Mylonites in the Blue Ridge
a. Triclinic deformation
b. Palinspastic restoration of the Blue Ridge in 3 dimensions.
c. Oblique convergence in Thornton Gap area.
6. Is there an unconformity between the Catoctin and the overlying sedimentary units?
7. New mica ages and their implications for deformation timing
a. Is this related to thrusting sequence?
b. Ages in the Swift Run and Weverton ages were likely the maximum temperature. Deeper rocks likely represent cooling ages.
8. Issue with the cover sequence west of the Blue Ridge - just where is the PreCambrian / Cambrian boundary?
a. Middle of the Chilhowee group?
b. Is all of the Chilhowee group Cambrian in age?
c. Is it in the Lynchburg formation?
9. Are there any Ediacaran fauna in any of the Neoproterozoic sediments?
10. There is a need to reconstruct paleoenvironments in the Blue Ridge
i.e. Mt. Rogers' glacial deposists, etc.
11. Paragneiss story
a. What is the time/temperature path these rocks took?
____________________________________________________
Again, I'd like to thank Amy, Matt, Laurie, and the rest of the dedicated staff of the Division of Geology and Mineral Resources for organizing the symposium and following up with this break-out session digest. Everyone I know who was there felt it was really useful. Facilitating discussions like these between geologic researchers is a key function of a robust state geology agency, and it chagrins me to think there will be less of this in future years due to the recent budget cuts.
What do you think of this list? Are these the most important issues in Blue Ridge geology? What would you add or refine?
I only attended the Blue Ridge session, and with the blessing of the conference organizers, I'd like to share the results of our ruminations here:
Unresolved issues in Blue Ridge Geology
General Outcomes:
Participants would like to see this as a start to a new state geologic map for 2015.
Participants would like have follow-up workshops to discuss these issues in detail.
Participants would like to develop research needs proposals on these key topics.
Specific Issues:
1. Ramp separating the Cambro-Ordovician carbonates from the rock of the Blue Ridge
a. What is its position?
b. Is it "thick" skinned?
c. Can field work (alone) resolve this?
d. What is its age?
How might this question be resolved?
A. Detailed geologic mapping at 1:24,000 scale across the Blue Ridge / Valley and Ridge transition
B. Applying geophysical techniques such as
a. Seismic reflection
b. Gravity studies
c. Reprocessing old data and reassessing old interpretations
C. LIDAR
2. Working out the problems with the Blue Ridge nomenclature and unit and fault correlations
a. Issues with variability in terminology and correlations across Virginia and between Virginia and North Carolina.
b. Map distribution of faults along the Blue Ridge - need to correlate their timing and extent
How might this question be resolved?
A. Detailed geologic mapping at 1:24,000 scale along the Blue Ridge (N/S) and across the Blue Ridge (E/W).
B. Models for the Blue Ridge need to be presented, discussed and synthesized.
C. Developing a basement "tool kit" for Late Proterozoic rocks: Since we can't afford to date every rock, there is a need for key characteristics for each unit to be agreed upon and applied in the field.
D. Expunge archaic terms and agree upon an appropriate vocabulary.
E. Regular focus group meetings and field meetings are necessary to resolve these issues.
3. When did the Blue Ridge develop its topographic relief?
a. Timing?
b. Is it in a steady state?
c. What is the history of the various erosional surfaces throughout the BR's evolution?
d. How does this correlate with the other physiographic provinces?
How might this question be resolved?
A. Detailed geologic mapping at 1:24,000.
B. Utilize low temperature chronometers such as U/Th/He at a sufficiently detailed spatial scale.
4. Role of the Mesozoic system in the Blue Ridge story and geometry.
How might this question be resolved?
A. Detailed geologic mapping at 1:24,000.
B. Need more geophysical studies.
C. Examine the effects/association of these fractures with water
D. Examine the relationship between features and mineral resource deposits
E. More detailed fracture studies are needed
F. Compare and contrast the Mesozoic rifting with previous rifting cycles
G. A seismic risk assessment needs to be done.
5. Mylonites in the Blue Ridge
a. Triclinic deformation
b. Palinspastic restoration of the Blue Ridge in 3 dimensions.
c. Oblique convergence in Thornton Gap area.
6. Is there an unconformity between the Catoctin and the overlying sedimentary units?
7. New mica ages and their implications for deformation timing
a. Is this related to thrusting sequence?
b. Ages in the Swift Run and Weverton ages were likely the maximum temperature. Deeper rocks likely represent cooling ages.
8. Issue with the cover sequence west of the Blue Ridge - just where is the PreCambrian / Cambrian boundary?
a. Middle of the Chilhowee group?
b. Is all of the Chilhowee group Cambrian in age?
c. Is it in the Lynchburg formation?
9. Are there any Ediacaran fauna in any of the Neoproterozoic sediments?
10. There is a need to reconstruct paleoenvironments in the Blue Ridge
i.e. Mt. Rogers' glacial deposists, etc.
11. Paragneiss story
a. What is the time/temperature path these rocks took?
____________________________________________________
Again, I'd like to thank Amy, Matt, Laurie, and the rest of the dedicated staff of the Division of Geology and Mineral Resources for organizing the symposium and following up with this break-out session digest. Everyone I know who was there felt it was really useful. Facilitating discussions like these between geologic researchers is a key function of a robust state geology agency, and it chagrins me to think there will be less of this in future years due to the recent budget cuts.
What do you think of this list? Are these the most important issues in Blue Ridge geology? What would you add or refine?
Labels: blue ridge, conferences, geology, virginia
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