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.

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.

Structure Evolution of Qinjiatun-Qindong Fault System in Lishu Subbasin

2013 ◽  
Vol 734-737 ◽  
pp. 170-177
Author(s):  
Shao Dong Qu ◽  
Chi Yang Liu ◽  
Li Jun Song ◽  
Hui Deng ◽  
Long Zhang ◽  
...  
Keyword(s):  
Fault Zone ◽  
Structure Analysis ◽  
Late Cretaceous ◽  
Seismic Data ◽  
Three Dimensional ◽  
Strike Slip ◽  
Fault System ◽  
Structure Evolution ◽  
Active Stage ◽  
Regional Stress

Three-dimensional(3-D) seismic data and structure analysis of the Lishu subasin in Songliao basin indicates that Qinjiatun fault zone is composed of two faults: East-Qin and West-Qin fault. This fault system initially formed at Huoshiling stage, peaked at Shahezi stage and faded dramatically from Yingcheng stage. The Qinjiatun fault was important in controlling strata thickness and distribution of the Huoshiling formation. Qindong fault, a typical strike-slip fault, developed relatively later, cutting the Qinjiatun fault, The major active stage was in Denglouku-Quantou stage, and weakened in the end of late Cretaceous. Qinjiatun fault zone was reversed at Denglouku stage when the regional stress went compressive, generating a structure nose that was potentially beneficial for hydrocarbon to accumulate. The strike-slip Qindong fault became active relatively later, cutting through the previous strata and proving pathways for both accumulation and effusion of hydrocarbon.

Cretaceous marine turtles from the Western Interior Seaway of Canada

1990 ◽  
Vol 27 (10) ◽  
pp. 1288-1298 ◽  
Author(s):  
Elizabeth L. Nicholls ◽  
Tim T. Tokaryk ◽  
Len V. Hills
Keyword(s):  
Relative Abundance ◽  
Late Cretaceous ◽  
Taxonomic Diversity ◽  
Western Interior Seaway ◽  
Niobrara Formation ◽  
Marine Turtles ◽  
Pierre Shale ◽  
Northern Areas ◽  
Lower Campanian ◽  
Upper Campanian

Late Cretaceous marine turtles are rare in Canada, but specimens are known from three formations: Toxochelys latiremis Cope and Protostega sp. from the Pierre Shale, Pembina Member (lower Campanian); Lophochelys niobrarae Zangerl and Chelonioidea genus indet. from the Bearpaw Formation (upper Campanian); Protostegidae genus indet. and one other taxon from the Niobrara Formation (Coniacian).The Canadian records of the listed taxa constitute the northernmost limits of their known range and may represent their northern limits in the Cretaceous inland sea. Taxonomic diversity and relative abundance of turtles in the Canadian samples are significantly less than in comparable faunas to the south. Cool marine climates may have excluded local nesting and discouraged migrations into northern areas.

scholarly journals Evidence for the Cretaceous sharkCretoxyrhina mantellifeeding on the pterosaurPteranodonfrom the Niobrara Formation

PeerJ ◽  
2018 ◽  
Vol 6 ◽  
pp. e6031 ◽  
Author(s):  
David W.E. Hone ◽  
Mark P. Witton ◽  
Michael B. Habib
Keyword(s):  
North America ◽  
Late Cretaceous ◽  
Fossil Record ◽  
Cervical Vertebra ◽  
Western Interior Seaway ◽  
Niobrara Formation ◽  
Intimate Association

A cervical vertebra of the large, pelagic pterodactyloid pterosaurPteranodonsp. from the Late Cretaceous Niobrara Formation of Kansas, USA is significant for its association with a tooth from the large lamniform shark,Cretoxyrhina mantelli. Though the tooth does not pierce the vertebral periosteum, the intimate association of the fossils—in which the tooth is wedged below the left prezygapophysis—suggests their preservation together was not mere chance, and the specimen is evidence ofCretoxyrhinabitingPteranodon. It is not possible to infer whether the bite reflects predatory or scavenging behaviour from the preserved material. There are several records ofPteranodonhaving been consumed by other fish, including other sharks (specifically, the anacoracidSqualicorax kaupi), and multiple records ofCretoxyrhinabiting other vertebrates of the Western Interior Seaway, but until now interactions betweenCretoxyrhinaandPteranodonhave remained elusive. The specimen increases the known interactions between large, pelagic, vertebrate carnivores of the Western Interior Seaway of North America during the Late Cretaceous, in addition to bolstering the relatively small fossil record representing pterosaurian interactions with other species.

scholarly journals Pre-inversion normal fault geometry controls inversion style and magnitude, Farsund Basin, offshore southern Norway

Solid Earth ◽  
2020 ◽  
Vol 11 (4) ◽  
pp. 1489-1510
Author(s):  
Thomas B. Phillips ◽  
Christopher A.-L. Jackson ◽  
James R. Norcliffe
Keyword(s):  
Late Cretaceous ◽  
Focal Point ◽  
Three Dimensional ◽  
Normal Fault ◽  
Fault System ◽  
Prior History ◽  
Plate Boundaries ◽  
Northern Margin ◽  
Long Wavelength ◽  
Structural Style

Abstract. Compressional strains may manifest along pre-existing structures within the lithosphere, far from the plate boundaries along which the causal stress is greatest. The style and magnitude of the related contraction is expressed in different ways, depending on the geometric and mechanical properties of the pre-existing structure. A three-dimensional approach is thus required to understand how compression may be partitioned and expressed along structures in space and time. We here examine how post-rift compressional strains are expressed along the northern margin of the Farsund Basin during Late Cretaceous inversion and Palaeogene–Neogene pulses of uplift. At the largest scale, stress localises along the lithosphere-scale Sorgenfrei-Tornquist Zone, where it is expressed in the upper crust as hangingwall folding, reverse reactivation of the basin-bounding normal fault, and bulk regional uplift. The geometry of the northern margin of the basin varies along strike, with a normal fault system passing eastward into an unfaulted ramp. Late Cretaceous compressive stresses, originating from the convergence between Africa, Iberia, and Europe, selectively reactivated geometrically simple, planar sections of the fault, producing hangingwall anticlines and causing long-wavelength folding of the basin fill. The amplitude of these anticlines decreases upwards due to tightening of pre-existing fault propagation folds at greater depths. In contrast, later Palaeogene–Neogene uplift is accommodated by long-wavelength folding and regional uplift of the entire basin. Subcrop mapping below a major, uplift-related unconformity and borehole-based compaction analysis show that uplift increases to the north and east, with the Sorgenfrei-Tornquist Zone representing a hinge line rather than a focal point to uplift, as was the case during earlier Late Cretaceous compression. We show how compressional stresses may be accommodated by different mechanisms within structurally complex settings. Furthermore, the prior history of a structure may also influence the mechanism and structural style of shortening that it experiences.

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