Recognition of an early Holocene polygonal fault system in Lake Superior: Implications for the compaction of fine-grained sediments

Geology ◽  
2004 ◽  
Vol 32 (3) ◽  
pp. 253 ◽  
Author(s):  
Joseph Cartwright ◽  
Nigel Wattrus ◽  
Deborah Rausch ◽  
Alastair Bolton
Keyword(s):  
Lake Superior ◽  
Early Holocene ◽  
Fault System ◽  
Fine Grained ◽  
Polygonal Fault

Geotechnical engineering significance of Great Plains polygonal fault system

2017 ◽  
Vol 54 (8) ◽  
pp. 1089-1103
Author(s):  
Andy St-Onge
Keyword(s):  
Great Plains ◽  
Upper Cretaceous ◽  
Geotechnical Engineering ◽  
Three Dimensional ◽  
Fault System ◽  
Niobrara Formation ◽  
Well Control ◽  
Fine Grained ◽  
Engineering Significance ◽  
Polygonal Fault

An extensive polygonal fault system (PFS) within fine-grained Upper Cretaceous sediments beneath the Great Plains of North America has implications for geotechnical engineering. Geological well control, outcrop, and three-dimensional seismic data from southeast Saskatchewan exemplify the fault characteristics typically observed within the PFS. The deepest faults are sparse, offset a seismic reflection identified from the Niobrara Formation Govenlock member, and have vertical offsets <2 m. The deformation increases in fault density and vertical offset at shallower depths, reaching 6 faults/km2 with up to 30 m of vertical offset. Upper Cretaceous strata throughout the Great Plains area are at or near outcrop, and the extensive PFS faulting and weathering have weakened the rock. This faulting and weakness have been observed and attributed to other factors such as glacial erosion, overconsolidation, swelling bentonite beds, or landslides from toe erosion at topographic slopes. The PFS faulting should be recognized as an extensive process to be considered when undertaking geotechnical analysis on the Great Plains where underlying Upper Cretaceous rocks exist. Engineering implications include road cuts, dam impoundments, building foundations, and natural slumping.

scholarly journals Seismic characteristics of polygonal fault systems in the Great South Basin, New Zealand

2020 ◽  
Vol 12 (1) ◽  
pp. 851-865
Author(s):  
Sukonmeth Jitmahantakul ◽  
Piyaphong Chenrai ◽  
Pitsanupong Kanjanapayont ◽  
Waruntorn Kanitpanyacharoen
Keyword(s):  
Three Dimensional ◽  
Late Eocene ◽  
Seismic Survey ◽  
Fault System ◽  
Normal Faults ◽  
Tier 2 ◽  
South Basin ◽  
Fault Systems ◽  
Tier 1 ◽  
Polygonal Fault

AbstractA well-developed multi-tier polygonal fault system is located in the Great South Basin offshore New Zealand’s South Island. The system has been characterised using a high-quality three-dimensional seismic survey tied to available exploration boreholes using regional two-dimensional seismic data. In this study area, two polygonal fault intervals are identified and analysed, Tier 1 and Tier 2. Tier 1 coincides with the Tucker Cove Formation (Late Eocene) with small polygonal faults. Tier 2 is restricted to the Paleocene-to-Late Eocene interval with a great number of large faults. In map view, polygonal fault cells are outlined by a series of conjugate pairs of normal faults. The polygonal faults are demonstrated to be controlled by depositional facies, specifically offshore bathyal deposits characterised by fine-grained clays, marls and muds. Fault throw analysis is used to understand the propagation history of the polygonal faults in this area. Tier 1 and Tier 2 initiate at about Late Eocene and Early Eocene, respectively, based on their maximum fault throws. A set of three-dimensional fault throw images within Tier 2 shows that maximum fault throws of the inner polygonal fault cell occurs at the same age, while the outer polygonal fault cell exhibits maximum fault throws at shallower levels of different ages. The polygonal fault systems are believed to be related to the dewatering of sedimentary formation during the diagenesis process. Interpretation of the polygonal fault in this area is useful in assessing the migration pathway and seal ability of the Eocene mudstone sequence in the Great South Basin.

Polygonal Fault System in the Paleogene of the Magallanes Foreland Basin, Southern Chile

2018 ◽  
Author(s):  
Jesús A. Pinto ◽  
Danilo L. González ◽  
Ángel P. González ◽  
Ricardo A. Zapata ◽  
Pablo E. Mella
Keyword(s):  
Foreland Basin ◽  
Fault System ◽  
Southern Chile ◽  
Polygonal Fault

Great Plains polygonal fault system as expressed in Saskatchewan: Late Cretaceous fault initiation and graben formation

2017 ◽  
Vol 54 (5) ◽  
pp. 477-493
Author(s):  
Andy St-Onge
Keyword(s):  
Great Plains ◽  
Late Cretaceous ◽  
Three Dimensional ◽  
Fault System ◽  
Western Interior Seaway ◽  
Niobrara Formation ◽  
Near Surface ◽  
M Current ◽  
Time Extension ◽  
Polygonal Fault

An extensive polygonal fault system (PFS) has been recognized in fine-grained Late Cretaceous sediments of the Western Interior Seaway of North America. Polygonal fault systems are pervasive organizations of nontectonic faults with fault traces that coalesce to form distinctive polygonal fault patterns. Interpretation of a three-dimensional seismic dataset from southeast Saskatchewan provides insight into fault initiation, timing, and geometry for the Great Plains PFS (GPPFS). Faulting initiates in the Niobrara Formation, with the largest fault throws occurring over Early Cretaceous Viking Formation sandstone accumulations, suggesting that drape compaction over the channel sand initiated some of the faulting. Above this, faulting increases in vertical offset, and the predominant fault strike angles change in the Lea Park, Belly River, and Bearpaw formations (all homotaxial to the Pierre Shale) throughout Campanian time. By late Bearpaw time, the initially almost random fault strike orientations change to well-defined northwest–southeast- and west–east-striking grabens. These grabens have up to 20 m of throw and can be 125 m wide and 900 m long at ∼400 m current depth. Predominant graben faults are the continuation of some of the deeper PFS faults. Moreover, the grabens are present over a Campanian clinoform bed and may be interpreted to indicate Bearpaw time extension tectonics that is local or regional in scale. The PFS helps to explain near-surface faulting observed in Late Cretaceous sediments in the Western Interior Seaway and could be used as a model to help explain Late Cretaceous geology, subsurface groundwater flow, and shallow natural gas reservoir continuity.

scholarly journals Formation of linear planform chimneys controlled by preferential hydrocarbon leakage and anisotropic stresses in faulted fine-grained sediments, offshore Angola

Solid Earth ◽  
2018 ◽  
Vol 9 (6) ◽  
pp. 1437-1468 ◽  
Author(s):  
Sutieng Ho ◽  
Martin Hovland ◽  
Jean-Philippe Blouet ◽  
Andreas Wetzel ◽  
Patrice Imbert ◽  
...  
Keyword(s):  
Stress State ◽  
Horizontal Stress ◽  
Lower Portion ◽  
Associated Gas ◽  
Fine Grained ◽  
Gas Leakage ◽  
Impermeable Barrier ◽  
Nucleation Sites ◽  
New Type ◽  
Polygonal Fault

Abstract. A new type of gas chimney exhibiting an unconventional linear planform is found. These chimneys are termed Linear Chimneys, which have been observed in 3-D seismic data offshore of Angola. Linear Chimneys occur parallel to adjacent faults, often within preferentially oriented tier-bound fault networks of diagenetic origin (also known as anisotropic polygonal faults, PFs), in salt-deformational domains. These anisotropic PFs are parallel to salt-tectonic-related structures, indicating their submission to horizontal stress perturbations generated by the latter. Only in areas with these anisotropic PF arrangements do chimneys and their associated gas-related structures, such as methane-derived authigenic carbonates and pockmarks, have linear planforms. In areas with the classic isotropic polygonal fault arrangements, the stress state is isotropic, and gas expulsion structures of the same range of sizes exhibit circular geometry. These events indicate that chimney's linear planform is heavily influenced by stress anisotropy around faults. The initiation of polygonal faulting occurred 40 to 80 m below the present day seafloor and predates Linear Chimney formation. The majority of Linear Chimneys nucleated in the lower part of the PF tier below the impermeable portion of fault planes and a regional impermeable barrier within the PF tier. The existence of polygonal fault-bound traps in the lower part of the PF tier is evidenced by PF cells filled with gas. These PF gas traps restricted the leakage points of overpressured gas-charged fluids along the lower portion of PFs, hence controlling the nucleation sites of chimneys. Gas expulsion along the lower portion of PFs preconfigured the spatial organisation of chimneys. Anisotropic stress conditions surrounding tectonic and anisotropic polygonal faults coupled with the impermeability of PFs determined the directions of long-term gas migration and linear geometries of chimneys. Methane-related carbonates that precipitated above Linear Chimneys inherited the same linear planform geometry, and both structures record the timing of gas leakage and palaeo-stress state; thus, they can be used as a tool to reconstruct orientations of stress in sedimentary successions. This study demonstrates that overpressure hydrocarbon migration via hydrofracturing may be energetically more favourable than migration along pre-existing faults.

Identification of polygonal faulting from legacy 3D seismic data in vintage Gulf of Mexico data using seismic attributes

2021 ◽  
pp. 1-17
Author(s):  
Karen M. Leopoldino Oliveira ◽  
Heather Bedle ◽  
Karelia La Marca Molina
Keyword(s):  
Seismic Data ◽  
Seismic Attributes ◽  
Fault System ◽  
3D Seismic ◽  
Seismic Attribute ◽  
Variable Amplitude ◽  
Attribute Analysis ◽  
Amplitude Data ◽  
3D Seismic Data ◽  
Polygonal Fault

We analyzed a 1991 3D seismic data located offshore Florida and applied seismic attribute analysis to identify geological structures. Initially, the seismic data appears to have a high signal-to-noise-ratio, being of an older vintage of quality, and appears to reveal variable amplitude subparallel horizons. Additional geophysical analysis, including seismic attribute analysis, reveals that the data has excessive denoising, and that the continuous features are actually a network of polygonal faults. The polygonal faults were identified in two tiers using variance, curvature, dip magnitude, and dip azimuth seismic attributes. Inline and crossline sections show continuous reflectors with a noisy appearance, where the polygonal faults are suppressed. In the variance time slices, the polygonal fault system forms a complex network that is not clearly imaged in the seismic amplitude data. The patterns of polygonal fault systems in this legacy dataset are compared to more recently acquired 3D seismic data from Australia and New Zealand. It is relevant to emphasize the importance of seismic attribute analysis to improve accuracy of interpretations, and also to not dismiss older seismic data that has low accurate imaging, as the variable amplitude subparallel horizons might have a geologic origin.

Early Holocene pinyon (Pinus monophylla) in the northeastern Great Basin

1990 ◽  
Vol 33 (1) ◽  
pp. 94-101 ◽  
Author(s):  
David B. Madsen ◽  
David Rhode
Keyword(s):  
Great Basin ◽  
Late Quaternary ◽  
Early Holocene ◽  
Hunter Gatherers ◽  
Pinus Monophylla ◽  
East Central ◽  
Lake Bonneville ◽  
Fine Grained ◽  
Pine Nut ◽  
Human Use

AbstractFine-grained excavation and analysis of a stratigraphic column from Danger Cave, northeastern Great Basin, suggests prehistoric hunter-gatherers were collecting and using singleleaf pinyon (Pinus monophylla) near the site for at least the last 7500 yr. Human use of the cave began after the retreat of Lake Bonneville from the Gilbert level, shortly before 10,000 yr B.P. In stratum 9, culturally deposited pine nut hulls appear in the sequence by about 7900 yr B.P. and are continuously present thereafter. A hull fragment in stratum 10 is directly dated to 7410 ± 120 yr B.P. These dates are at least 2000 yr earlier than expected by extrapolation to macrofossil records from the east-central and central Great Basin, and necessitate some revision of current biogeographical models of late Quaternary pinyon migration.

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