SIGNFICANCE OF AN ESE FRACTURE DIRECTION IN TERTIARY ... · Slim Buttes Study Area Toadstool Study...
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SIGNFICANCE OF AN ESE FRACTURE DIRECTION IN TERTIARY STRATA OF SOUTH DAKOTA AND NEBRASKA? ABSTRACT: A rich array of fracture types in the Tertiary strata of Nebraska and South Dakota includes faults (predominantly normal), clastic dikes, veins (chalcedony, calcite and gypsum), joints, and occasional deformation bands. These fractures show a diverse array of morphologies orientation distributions and complex age relationships. Generally north trending features can be associ- ated with reactivation of Laramide features (a ‘Black Hills’ trend). More NE to ENE trending structures have been associated with reactivation of basement fea- tures such as those along the Colorado Lineament. The Toadstool fault in north- west Nebraska falls in this category. However, a significant ESE to SE trending and regionally distributed set of features is largely unrecognized and unex- plained. These features include normal faults and conjugate joints at Slim Buttes and Pine Hills in NW South Dakota, faults and clastic dikes in Badlands Na- tional Park, the White Clay fault in NW Nebraska, one of several fault and joint and chalcedony vein directions at Toadstool Geologic Park in NW Nebraska, and a joint set in Brule Formation strata in the North Platte River valley area of Nebraska. The faults and joints at Slim Buttes clearly formed before the uncon- formably overlying Arikaree Group strata were deposited. The White Clay fault is argued to have been active during and influenced the deposition of the basal Ogallala Group strata. The ESE trending faults at Toadstool postdate diageneti- cally produced silica mobilization and chalcedony vein formation, which is pos- sibly coeval with Arikaree Group deposition and loading. Explanations for the regional ESE direction of fracturing include: a) reactivation over time of a con- sistently oriented, but unidentified, structural element; b) loading by a regionally consistent stress field that persisted from pre- to post- Arikaree Group deposition times; or c) loading by a regionally consistent stress field during an earlier and shorter time frame, followed by subsequent reactivation. The third possibility is favored at present with a pre-Arikaree inception of fracturing. MAHER, Harmon Jr, Department of Geography/Geology, University of Nebraska at Omaha, Omaha, NE 68182, [email protected] and SHUSTER, Robert D., Univ Nebraska - Omaha, Dept Geography & Geology, Omaha, NE 68182-0199 Slim Buttes Study Area Toadstool Study area Big Badlands Study Area Rock Bass Study Area Multiple working hypothesis framework <- NNE angular unconformity with overlying Arikaree Grp. strata tilte d Brul eFm. strata Stereoplot of poles to joints in Brule Fm. strata. Note tilted ESE trending set. Contour interval 2%, n = 111 Stereoplot of poles to joints in Arikaree Grp. strata. Note very different pattern. Contour interval 2%, n = 117 Similarly oriented faults in West Short Pine Hills 50 km to W of Slim Buttes. Take aways: - ESE oriented array of normal faults - ESE oriented array of joints - both formed before Arikaree Grp. deposition. - associated detachment - cause enigmatic, but not river valley slumps Map from Gill 1962 Map from Gill 1962 Gill (1962) -> landslide blocks along pre-Arikaree valleys. Gill, J. R., 1962, Tertiary Landslides, Northwestern South Dakota and southeastern Montana, GSA Bulletin, 73, 725-736 Lillegraven (1970) -> 15 reasons not landslide blocks, gravity controlled detachment fault perhaps akin to Heart Mountain detachment. Lillegraven, J. A., 1970, Stratigraphy, Structure and Vertebrate Fossils of the Oligocene Brule Formation, Slim Buttes, Northwestern South Dakota: GSA Bulletin, 81, 831-850. Cause? rotated conjugate joints joint cluster w fault core clastic dikes Overview Map of Various Study Areas 100 200 5 13 21 29 37 45 53 61 69 77 85 93 101 109 117 125 133 141 149 157 165 173 189 197 205 213 221 229 237 245 253 261 269 277 285 293 301 309 317 325 333 341 349 357 n= 968 Above: Normal faults showing soft-sediment style. Right: Sliding sector plot of dike strikes modeled as two preferred orientations and a uni- form component. . Left: Map showing dike strikes and inter- preted dike pattern. The pattern is complex, but a distinct ESE trend exists. Below: Ex- ample of cross cutting relationships. Differ- ent directions are basically coeval. Take aways: - ESE oriented array of normal faults - ESE oriented array of clastic dikes - faults preceded dikes (?). - dikes reactivated earlier grain - dikes post-Sharps Fm. in age Map showing study site. Green strike symbols show the strike and dip direction of normal faults. Blue strike symbols are strike of subvertical chalcedony veins. The orange dots represent the axis of shoe-string sandstone channels. Take aways: - there is a dominant SE trending faults in Chadron Fm. strata . - these faults post-date chalcedonay vein formation and associated diagenesis. - fault coeval with later calcite phase - modeling indicates a significant preferred chalcedony vein orientation at 115 20 60 100 5 13 21 29 37 45 53 61 69 77 85 93 101 109 117 125 133 141 149 157 165 173 181 189 197 205 213 221 229 237 245 253 261 269 277 285 293 301 309 317 325 333 341 349 357 P1 P2 P3 P4 uniform azimuth 115 77 161 12 NA n= 498 sample % 12% 8% 6% 4% 70% % difference = 5% standard deviation 10 10 12 14 NA Rock Bass Map showing normal fault strikes (red) and strikes of local chalcedony vein array (blue), from the southern portion of the Toadstool Geologic Park study site. Note the fairly well de- veloped SE to ESE trend. Underlying image USGS air photos. 40 80 120 160 5 13 21 29 37 45 53 61 69 77 85 93 101 109 117 125 133 141 149 157 165 173 181 189 197 205 213 221 229 237 245 253 261 269 277 285 293 301 309 317 325 333 341 349 357 P1 P2 P3 P4 uniform azimuth 101 54 9 148 NA n= 598 sample % 36% 35% 20% 8% 1% % difference = 6% standard deviation 11 10 12 11 NA Toadstool Take aways: - there is a ESE chalcedony vein preferred orientation in Chadron Fm. strata. - faults are normal and multidirectional, but a SE to ESE trending and asymmetric array exists (similar to the rela- tionships seen at Rock Bass). - An earlier set of NE trending normal faults is part of the Colorado lineament as defined by Werner, L. A., 1978, The Colorado Lineament: A middle Precambrian wrench fault system; Geol. Soc. Am. Bulletin, v. 89, 161-171. 108 64 Above: Sliding sector plot of chalcedony veins. The blue line represents the model with model pa- rameters given in the table below. Note the 101 trending preferred orientation. Below: Stereoplot of Kamb contour plot of poles to 748 faults. A complex distribution exists. Shown in red is a representation of the ESE and south dip- ping fault set. These faults cut the NE trending set. Conclusions: - The Tertiary fracture history of the Great Plains is complex and polyphase, requiring an extensive data acquisition campaign and a multiple hypothesis framework to understand. - A suite of similarly oriented normal faults, clastic dike, chalcedony veins and joints at Slim Buttes, the Big Badlands, the White Clay area, Toadstool Geologic Park suggest a regionally coherent SE to ESE oriented fracture system exists. - At Slim Buttes faulting is clearly pre-Arikaree Group. At the Badlands it preceded lithification and clastic dike emplacement. At Toadstool it is syn- to post- chalcedony vein formation which is associated with signficant diagenesis and silica mobilization. At White Clay it is of Ogallala Group age. ESE oriented normal faulting, veining and joint- ing persisted for a significant period of time. - While N to NE oriented structures may reflect Colorado Lineament basement reactivation trends, and more N-S oriented structures may reflect reactivation of Laramide trends, the significant ESE orientation may reflect local reactivation of a basement grain and/or a persistent Tertiary regional stress field. Acknowledgements: This work was not possible without the sub- stantial contributions of a large cadre of undergraduate students. Pe- troleum Research Fund of the American Chemical Society provided funding for a significant part of this work. 0 Ma Time line Arikaree Group White Clay Gravel Beds & ESE faulting SE faulting at Slim Buttes White River Group Ogallala Group end of Laramide 40 Ma 10 Ma 20 Ma 30 Ma 40 Ma Eocene Oligocene Miocene Pliocene ? Big Badlands clastic dikes ? Agate Springs ENE faulting ? ESE faulting at Rock Bass &Toadstool Big Badlands ESE faulting NNE faulting at Toadstool ? ESE joint formation North Platte R.Valley Timing based on a combination of: age of host rock, structural truncation by unconformities, style of deformation, and models for local diagenetic history. Rein- terpretation likely. Cropped images of aeromagnetic map of western South Dakota and Ne- braska taken from USGS site: http://mrdata.usgs.go v/catalog/cite-- view.php?cite=70 and http://pubs.usgs.gov/ ds/2005/138/ These images can give some guide as to basement fabrics that might be reacti- vated. Map from Fielding et al. (Fielding, C. , LaGarry, H. E. , LaGarry, L. A., Bailey, B. E., & Swinehart, J. B., 2007, Sedimentology of the Whiteclay Gravel Beds (Ogallala Group) in northwestern Nebraska, USA: Structurally controlled drainage promoted by Early Miocene uplift of the Black Hills Dome; Sedimentary Geology, 202, 58–71.) showing the White Clay Fault Zone. “Fault rupture topog- raphy facilitated formation of a steep-sided canyon, or valley, up to 20 m deep, being virtu- ally straight with sharp bends at intervals of sev- eral km.” How to get to failure envelope? increasing pore pressure increase differential stress confined system unconfined system aquathermal pressurization tectonic compaction increase vertical load raise groundwater table chemical reactions contraction confined volume change expansion thermo-elastic chemical strain weakening change fluid density change horizontal load increase vertical load changing Poisson’s ratio Triggering geologic events: bc) burial and compaction, dg) deglaciation, di) diagenesis, dp) diapirism, dc) differential compaction, eu) erosional unloading, er) erosional relief generation, gh) geothermal heating, gl) glaciation, gw) groundwater flow change, ic) igneous cooling, im) impact, ke) karst and/or evaporite dissolution, ld) localized deformation, om) organic maturation, ov) overthrusting, pl) plate boundary forces, td) tectonic denudation . Three ways to get failure: 1) shift stress circle to left and/or 2) grow circle larger and/or 3) move failure envelope to stress circle normal stress shear stress failure envelope dg, om er, gw, ic, td pl, dp, dc, gl, ke, ld pl, ld gh, ov bc, ov, im, er gh, di bc, gl, ov bc, gl, tr Poisson’s contraction (unloading) dg, eu, td expansion contraction di di, om Imge of chalcedony vein and fault North Platte River valley Images: Fractures be- neath the Arikaree-Brule Fm. contact. Note ero- sional scour along frac- ture to right. Replotted and modeled data from Wang, S., 1998, UNL Ph.D. thesis Take aways: - ESE joint set here. - may be pre- Arikaree in age Images of ESE trending normal faults in Brule Formation strata at Toadstool Base map: Garrity, C. P. & Soller, D. R., 2009, Database of the Geologic Map of North America – Adapted from the Map by J. C. Reed, Jr. and others (2005); United States Geological Survey Data Series 424, 1 CD. http://pubs.usgs.gov/ds/424/ and pubs.usgs.gov/ds/424/ds424_text.pdf . Strike symbols of dominant vein/joint directions. Inset boxes are color coded to study areas discussed. Clipped part of Badlands National Park Geologic Map: Ray- mond & King, 1976, USGS Map I-934 ,17 United States Nuclear Regulatory Commission Official Hearing Exhibit In the Matter of: CROW BUTTE RESOURCES, INC. (License Renewal for the In Situ Leach Facility, Crawford, Nebraska) ASLBP #: 08-867-02-OLA-BD01 Docket #: 04008943 Exhibit #: Identified: Admitted: Withdrawn: Rejected: Stricken: Other: INT-060-00-BD01 8/18/2015 8/18/2015
Transcript of SIGNFICANCE OF AN ESE FRACTURE DIRECTION IN TERTIARY ... · Slim Buttes Study Area Toadstool Study...
SIGNFICANCE OF AN ESE FRACTURE DIRECTION IN TERTIARY STRATA OF SOUTH DAKOTA AND NEBRASKA?
ABSTRACT: A rich array of fracture types in the Tertiary strata of Nebraska and South Dakota includes faults (predominantly normal), clastic dikes, veins (chalcedony, calcite and gypsum), joints, and occasional deformation bands. These fractures show a diverse array of morphologies orientation distributions and complex age relationships. Generally north trending features can be associ-ated with reactivation of Laramide features (a ‘Black Hills’ trend). More NE to ENE trending structures have been associated with reactivation of basement fea-tures such as those along the Colorado Lineament. The Toadstool fault in north-west Nebraska falls in this category. However, a significant ESE to SE trending and regionally distributed set of features is largely unrecognized and unex-plained. These features include normal faults and conjugate joints at Slim Buttes and Pine Hills in NW South Dakota, faults and clastic dikes in Badlands Na-tional Park, the White Clay fault in NW Nebraska, one of several fault and joint and chalcedony vein directions at Toadstool Geologic Park in NW Nebraska, and a joint set in Brule Formation strata in the North Platte River valley area of Nebraska. The faults and joints at Slim Buttes clearly formed before the uncon-formably overlying Arikaree Group strata were deposited. The White Clay fault is argued to have been active during and influenced the deposition of the basal Ogallala Group strata. The ESE trending faults at Toadstool postdate diageneti-cally produced silica mobilization and chalcedony vein formation, which is pos-sibly coeval with Arikaree Group deposition and loading. Explanations for the regional ESE direction of fracturing include: a) reactivation over time of a con-sistently oriented, but unidentified, structural element; b) loading by a regionally consistent stress field that persisted from pre- to post- Arikaree Group deposition times; or c) loading by a regionally consistent stress field during an earlier and shorter time frame, followed by subsequent reactivation. The third possibility is favored at present with a pre-Arikaree inception of fracturing.
MAHER, Harmon Jr, Department of Geography/Geology, University of Nebraska at Omaha, Omaha, NE 68182, [email protected] and SHUSTER, Robert D., Univ Nebraska - Omaha, Dept Geography & Geology, Omaha, NE 68182-0199
Slim Buttes Study Area
Toadstool Study area
Big Badlands Study Area
Rock Bass Study Area
Multiple working hypothesis framework
<- NNE angular unconformity with overlying Arikaree Grp. strata
tilted Brule Fm. strata
Stereoplot of poles to jointsin Brule Fm. strata. Note tilted ESE trending set.
Contour interval 2%, n = 111
Stereoplot of poles to jointsin Arikaree Grp. strata. Note
very different pattern. Contour interval 2%, n = 117
Similarly oriented faults in West Short Pine Hills 50 km to W of Slim Buttes.
Take aways:- ESE oriented array of normal faults- ESE oriented array of joints- both formed before Arikaree Grp. deposition.- associated detachment- cause enigmatic, but not river valley slumps
Map from Gill 1962
Map from Gill 1962
Gill (1962) -> landslide blocks along pre-Arikaree valleys. Gill, J. R., 1962, Tertiary Landslides, Northwestern South Dakota and southeastern Montana, GSA Bulletin, 73, 725-736
Lillegraven (1970) -> 15 reasons not landslide blocks, gravity controlled detachment faultperhaps akin to Heart Mountain detachment. Lillegraven, J. A., 1970, Stratigraphy, Structure and Vertebrate Fossils of the Oligocene Brule Formation, Slim Buttes, Northwestern South Dakota: GSA Bulletin, 81, 831-850.
Cause?
rotated conjugate jointsjoint cluster w fault coreclastic dikes
Overview Map of Various Study Areas
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n= 968
Above: Normal faults showing soft-sediment style. Right: Sliding sector plot of dike strikes modeled as two preferred orientations and a uni-form component. .
Left: Map showing dike strikes and inter-preted dike pattern. The pattern is complex, but a distinct ESE trend exists. Below: Ex-ample of cross cutting relationships. Differ-ent directions are basically coeval.
Take aways:- ESE oriented array of normal faults- ESE oriented array of clastic dikes- faults preceded dikes (?).- dikes reactivated earlier grain- dikes post-Sharps Fm. in age
Map showing study site. Green strike symbols show the strike and dip direction of normal faults. Blue strike symbols are strike of subvertical chalcedony veins. The orange dots represent the axis of shoe-string sandstone channels.
Take aways:- there is a dominant SE trending faults in Chadron Fm. strata .- these faults post-date chalcedonay vein formation and associated diagenesis.- fault coeval with later calcite phase- modeling indicates a significant preferred chalcedony vein orientation at 115
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P1 P2 P3 P4 uniform azimuth 115 77 161 12 NA
n= 498
sample % 12% 8% 6% 4% 70%
% difference = 5%
standard deviation 10 10 12 14 NA
Rock Bass
Map showing normal fault strikes (red) and strikes of local chalcedony vein array (blue), from the southern portion of the Toadstool Geologic Park study site. Note the fairly well de-veloped SE to ESE trend. Underlying image USGS air photos.
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P1 P2 P3 P4 uniformazimuth 101 54 9 148 NA
n= 598
sample % 36% 35% 20% 8% 1%
% difference = 6%
standard deviation 11 10 12 11 NA
Toadstool
Take aways:- there is a ESE chalcedony vein preferred orientation in Chadron Fm. strata.- faults are normal and multidirectional, but a SE to ESE trending and asymmetric array exists (similar to the rela-tionships seen at Rock Bass). - An earlier set of NE trending normal faults is part of the Colorado lineament as defined by Werner, L. A., 1978, The Colorado Lineament: A middle Precambrian wrench fault system; Geol. Soc. Am. Bulletin, v. 89, 161-171.
108 64
Above: Sliding sector plot of chalcedony veins. The blue line represents the model with model pa-rameters given in the table below. Note the 101 trending preferred orientation.
Below: Stereoplot of Kamb contour plot of poles to 748 faults. A complex distribution exists. Shown in red is a representation of the ESE and south dip-ping fault set. These faults cut the NE trending set.
Conclusions:- The Tertiary fracture history of the Great Plains is complex and polyphase, requiring an extensive data acquisition campaign and a multiple hypothesis framework to understand.- A suite of similarly oriented normal faults, clastic dike, chalcedony veins and joints at Slim Buttes, the Big Badlands, the White Clay area, Toadstool Geologic Park suggest a regionally coherent SE to ESE oriented fracture system exists.- At Slim Buttes faulting is clearly pre-Arikaree Group. At the Badlands it preceded lithification and clastic dike emplacement. At Toadstool it is syn- to post- chalcedony vein formation which is associated with signficant diagenesis and silica mobilization. At White Clay it is of Ogallala Group age. ESE oriented normal faulting, veining and joint-ing persisted for a significant period of time. - While N to NE oriented structures may reflect Colorado Lineament basement reactivation trends, and more N-S oriented structures may reflect reactivation of Laramide trends, the significant ESE orientation may reflect local reactivation of a basement grain and/or a persistent Tertiary regional stress field.Acknowledgements: This work was not possible without the sub-stantial contributions of a large cadre of undergraduate students. Pe-troleum Research Fund of the American Chemical Society provided funding for a significant part of this work.
0 MaTime line
Arikaree GroupWhite Clay Gravel
Beds & ESE faultingSE faulting at Slim Buttes
White River Group
Ogallala Groupend ofLaramide
40 Ma
10 Ma20 Ma30 Ma40 MaEocene Oligocene Miocene Pliocene
?
Big Badlands clastic dikes?
Agate SpringsENE faulting
?
ESE faulting at Rock Bass &Toadstool
Big BadlandsESE faulting
NNE faulting at Toadstool
?
ESE joint formationNorth Platte R.Valley
Timing based on a combination of: age of host rock, structural truncation by unconformities, style of deformation, and models for local diagenetic history. Rein-terpretation likely.
Cropped images of aeromagnetic map of western South Dakota and Ne-braska taken from USGS site: http://mrdata.usgs.gov/catalog/cite--view.php?cite=70 andhttp://pubs.usgs.gov/ds/2005/138/ These images can give some guide as to basement fabrics that might be reacti-vated.
Map from Fielding et al. (Fielding, C. , LaGarry, H. E. , LaGarry, L. A., Bailey, B. E., & Swinehart, J. B., 2007, Sedimentology of the Whiteclay Gravel Beds (Ogallala Group) in northwestern Nebraska, USA: Structurally controlled drainage promoted by Early Miocene uplift of
the Black Hills Dome; Sedimentary Geology, 202, 58–71.) showing the White Clay Fault Zone. “Fault rupture topog-raphy facilitated formation of a steep-sided canyon, or valley, up to 20 m deep, being virtu-ally straight with sharp bends at intervals of sev-eral km.”
How to get to failure envelope?
increasingpore
pressureincrease
differential stress
confined systemunconfined
system aquathermalpressurization
tectoniccompaction
increasevertical
loadraise
groundwatertable
chemicalreactions
contraction
confinedvolume change
expansion
thermo-elastic chemical
strainweakening
changefluiddensity change
horizontalload increase
verticalload
changing Poisson’s
ratio
Triggering geologic events: bc) burial and compaction, dg) deglaciation, di) diagenesis, dp) diapirism, dc) differential compaction, eu) erosional unloading, er) erosional relief generation, gh) geothermal heating, gl) glaciation, gw) groundwater flow change, ic) igneous cooling, im) impact, ke) karst and/or evaporite dissolution, ld) localized deformation, om) organic maturation, ov) overthrusting, pl) plate boundary forces, td) tectonic denudation .
Three ways to get failure:1) shift stress circle to left and/or
2) grow circle larger and/or 3) move failure envelope to stress circle normal stress
shea
r st
ress
failure envelope
dg, om
er, gw, ic, td pl, dp, dc, gl, ke, ldpl, ld
gh, ov
bc, ov, im, er
gh, di
bc, gl, ovbc, gl, tr
Poisson’s contraction(unloading) dg, eu, td
expansion
contraction
di
di, om
Imge of chalcedony vein and fault
North Platte River valley
Images: Fractures be-neath the Arikaree-Brule Fm. contact. Note ero-sional scour along frac-ture to right.
Replotted and modeled data from Wang, S., 1998, UNL Ph.D. thesis
Take aways:- ESE joint set here.- may be pre-Arikaree in age
Images of ESE trending normal faults in Brule Formation strata at Toadstool
Base map: Garrity, C. P. & Soller, D. R., 2009, Database of the Geologic Map of North America – Adapted from the Map by J. C. Reed, Jr. and others (2005); United States Geological Survey Data Series 424, 1 CD. http://pubs.usgs.gov/ds/424/ and pubs.usgs.gov/ds/424/ds424_text.pdf . Strike symbols of dominant vein/joint directions. Inset boxes are color coded to study areas discussed.
Clipped part of Badlands National Park Geologic Map: Ray-mond & King, 1976, USGS Map I-934
United States Nuclear Regulatory Commission Official Hearing Exhibit In the Matter of: CROW BUTTE RESOURCES, INC.
(License Renewal for the In Situ Leach Facility, Crawford, Nebraska)
ASLBP #: 08-867-02-OLA-BD01 Docket #: 04008943 Exhibit #: Identified: Admitted: Withdrawn: Rejected: Stricken:
Other:
INT-060-00-BD01 8/18/20158/18/2015
