Interaction between Strike-Slip and Thrust-Shear: Deformation of the Bullbreen Group, Central-Western Spitsbergen

Ratliff, Richard G.; Morris, Alan P.; Dodt, Matthew E.

doi:10.1086/629224

Cited by 14 publications

(5 citation statements)

References 22 publications

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“…Assuming equal increments of strain, we can determine a theoretical path for the model of the deformation at Durmid Hill and predict a finite strain state using (1). The effects of the order of premultiplication of the two deformation matrices (simple and pure shear) are minimal if small strain increments are used [Ramsay, 1967;Ratlift et al, 1988]. Using the incremental strains given in the last section 30 increments of swain were applied, and the results are illustrated in Figure 8.…”

Section: Deformation Path and Finite Strainmentioning

confidence: 99%

Transpression along the Southern San Andreas Fault, Durmid Hill, California

Bürgmann¹

1991

Tectonics

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Transpression is expressed at Durmid Hill in the development and subsequent rotation of en 6chelon folds and ongoing vertical uplift. The transpression-related strain field can be quantified by an analysis of (1) orientation of rotated fold axes, which display an angle of about 20 ø between the San Andreas fault and the fold-axial traces; (2) shortening perpendicular to the fold axes (40%-60%); (3) extension parallel to the fold axes (58%-68%), measured using a boudinaged ash bed; and (4) uplift determined from an antecedent stream (1.1-1.7 mm/yr), the topographic expression of Durmid Hill, and the exposed stratigraphy. The observed deformation may be approximated by a homogeneous, transpressional deformation. This model suggests that an estimated 9%-14% of the total displacement predicted by plate motion models across the San Andreas fault has been accommodated by the Durmid Hill deformation zone adjacent to the fault. This off-fault deformation is not directly coupled to coseismic or interseismic movement on the fault itself. INTRODUCTION Transpression (i.e., a combination of strike-slip shear and shortening perpendicular to the shear zone) has been identified recently in many areas that were thought to have undergone either pure shortening or simple shear deformation. Where shortening is the dominant deformation mode, a component of strike-slip shear is recognized primarily by significant extension parallel to fold axes [e.g., Hatland, 1971; Ratschbacher, 1986; Ratliff et al., 1988]. In strike-slip fault systems transpressional segments can be recognized by uplift and the development of compressional features such as flower structures [e.g., Harding and Lowell, 1979]. The component of shortening is postulated to be dependent on the angle between the strike of the fault and the plate vector determined by relative plate motion calculations. The Durmid Hill, southern California, area offers a unique example of deformation of layered, soft lacustrine sedimentary rocks near a major strike-slip fault, reminiscent of a macroscale clay model [Odonne and Vialon, 1983; Wilcox et al., 1973]. Here these models can be directly compared to deformation in a natural environment. In this study, the strain field of a segment of the southern San Andreas fault (SAF) at Durmid Hill (Figure 1) is quantified and compared with the theoretical strain field of a transpressional shear zone. Shortening perpendicular to fold axes, axial parallel extension, orientation of fold axes, and estimated vertical uplift rates and magnitudes are used as strain indicators. The implications of the observed deformation at Pal:•r number 91TC01443. 0278-7407/91/91TC-01443 $10.00 Durmid Hill for fault displacement studies and the tectonic style in the area are discussed. Stratigraphy and Crustal StructureThe geology of Durmid Hill was described by Babcock [1969, 1974] and Dibblee [1954]. Two late Cenozoic units are exposed in the area: the Shavers Well Formation (identified as Palm Spring Formation by Dibblee [1954]) and the Borrego Formation. The Shave...

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Section: Deformation Path and Finite Strainmentioning

confidence: 99%

Transpression along the Southern San Andreas Fault, Durmid Hill, California

Bürgmann¹

1991

Tectonics

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“…410 Ma) age and possibly coeval with D2 in the remaining basement (Labrousse et al 2008;Michalski et al 2014;Morris 1988). The local NNW-SSE trending dextral shearing and related thrusting recorded in the western Bullbreeen Group (Ratliff et al 1988) can be attributed to the same event. Superimposed on the pre-mid-Carboniferous structures are D3 and D4, which are related to the development of the West Spitsbergen Fold and Thrust Belt (WSFTB) during the Eurekan deformation.…”

Section: Prins Karls Forland and Oscar II Landmentioning

confidence: 80%

Early Devonian sinistral shearing recorded by retrograde monazite-(Ce) in Oscar II Land, Svalbard

et al. 2022

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The Southwestern Basement Province of Svalbard extends northward from Sørkapp Land in the south to Oscar II Land. In the north, the Müllerneset Formation characterized by polymetamorphosed Proterozoic sedimentary rocks crops out. In this study we used an integrated tectonic and petrochronological approach to gain an insight into the structural and metamorphic evolution of the unit and surrounding basement. The Müllerneset Formation consists of two separate tec-tonic blocks. NNW-SSE trending retrograde foliation is associated with mineral and stretching lineation and kinematic indicators consistent with left-lateral to oblique sinistral shearing in the western block. The eastern block is characterized by the opposite sense of shear that was overturned during the Eurekan event as evidenced by unconformably overlaying Carboniferous sedimentary rocks. Conventional geothermobarometry yields the prograde peak pressure metamorphic conditions of 6.6 - 7.1 kbar at 480 - 520°C followed by peak temperature at 5.1 - 5.9 kbar and 530 - 560°C. Subsequent retrograde greenschist facies overprint is related to left-lateral NNW-SSE trending shearing. Tiny monazite occurs within foliation or overgrows allanite-(Ce), thus is interpreted as growth along a retrograde path. Th-U-total Pb dating of monazite-(Ce) provided an early Caledonian age (ca. 450 Ma) and younger population of ca. 410 ± 8 Ma. This age is consistent with previously reported 40Ar/39Ar cooling ages (410 ± 2 Ma) of muscovite supporting a retrograde growth of monazite. Petrochronological evidence combined with structural observations suggests that the Müllerneset Formation has been tectonically exhumed in the Early Devonian due to the NNW-SSE trending left-lateral shearing. Coeval folding and thrusting in the remaining basement of Oscar II Land to the east indicate a transpressional regime of the deformation in the Early Devonian. Similarly oriented contemporaneous tectonic zones within the Southwestern Basement Province of Svalbard may account for the same set of shear zones dispersing the Ordovician subduction complexes along western Spitsbergen.

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“…2) The cause of this deformation event was probably NS compression activating a NW-SE trending strike-slip fault that marked the SW limit of the Bullbreen basin; the resultant interaction between dextral strike-slip and compression was limited to a narrow zone along this fault (Ratliff et al 1988).…”

Section: Discussionmentioning

confidence: 99%

“…The upper package contains evidence for two principal deformation events. The first occurred during approximately NS compression and concomitant dextral strike-slip along the basin margins (Ratliff et al 1988), and produced Slb, associated north verging folds and northerly directed thrusting. A second major event involved easterly directed thrusting and/or reverse faulting.…”

Section: Upper Packagementioning

confidence: 99%

Polyphase deformation in Oscar II Land, central western Svalbard

Morris

1988

Polar Research

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Morris, A. 1988: Polyphase deformation in Oscar I1 Land, central western Svalbard. Polar Research 6 , 6W4. Pre-Carboniferous rocks in central western Svalbard can be divided into two rock packages that have experienced three phases of deformation. The lower package includes upper Proterozoic sediments, the upper package is of upper Ordovician to lower Silurian age. Pre-upper Ordovician (Caledonian) deformation is characterized by north-south fold-axes, and is recorded in the lower package only. Following the Ordovician, east-west fold axes developed in the upper package but only locally in the lower. The third phase, probably Tertiary in age, produced easterly directed thrusting, and refolding about sub-horizontal. north-south fold axes in both packages, This complex structural history has resulted in tectonic thickening of the rock sequences by refolding and thrusting which has not been recognized by previous workers.

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Interaction between Strike-Slip and Thrust-Shear: Deformation of the Bullbreen Group, Central-Western Spitsbergen

Cited by 14 publications

References 22 publications

Transpression along the Southern San Andreas Fault, Durmid Hill, California

Transpression along the Southern San Andreas Fault, Durmid Hill, California

Early Devonian sinistral shearing recorded by retrograde monazite-(Ce) in Oscar II Land, Svalbard

Polyphase deformation in Oscar II Land, central western Svalbard

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