scholarly journals From widespread Mississippian to localized Pennsylvanian extension in central Spitsbergen, Svalbard

Solid Earth ◽  
2018 ◽  
Vol 9 (6) ◽  
pp. 1535-1558
Author(s):  
Jean-Baptiste P. Koehl ◽  
Jhon M. Muñoz-Barrera
Keyword(s):  
Sedimentary Rocks ◽  
Fault Zones ◽  
Normal Faults ◽  
Late Devonian ◽  
Growth Strata ◽  
Tectonic Events ◽  
Basement Rocks ◽  
Field Evidence ◽  
History Of ◽  
Tectonic Settings

Abstract. In the Devonian–Carboniferous, a rapid succession of clustered extensional and contractional tectonic events is thought to have affected sedimentary rocks in central Spitsbergen, Svalbard. These events include Caledonian post-orogenic extensional collapse associated with the formation of thick Early–Middle Devonian basins, Late Devonian–Mississippian Ellesmerian contraction, and Early–Middle Pennsylvanian rifting, which resulted in the deposition of thick sedimentary units in Carboniferous basins like the Billefjorden Trough. The clustering of these varied tectonic settings sometimes makes it difficult to resolve the tectono-sedimentary history of individual stratigraphic units. Notably, the context of deposition of Mississippian clastic and coal-bearing sedimentary rocks of the Billefjorden Group is still debated, especially in central Spitsbergen. We present field evidence (e.g., growth strata and slickensides) from the northern part of the Billefjorden Trough, in Odellfjellet, suggesting that tilted Mississippian sedimentary strata of the Billefjorden Group deposited during active (Late/latest?) Mississippian extension. WNW–ESE-striking basin-oblique faults showing Mississippian growth strata systematically die out upwards within Mississippian to lowermost Pennsylvanian strata, thus suggesting a period of widespread WNW–ESE-directed extension in the Mississippian and an episode of localized extension in Early–Middle Pennsylvanian times. In addition, the presence of abundant basin-oblique faults in basement rocks adjacent to the Billefjorden Trough suggests that the formation of Mississippian normal faults was partly controlled by reactivation of preexisting Neoproterozoic (Timanian?) basement-seated fault zones. We propose that these preexisting faults reactivated as transverse or accommodation cross faults in or near the crest of transverse folds reflecting differential displacement along the Billefjorden Fault Zone. In Cenozoic times, a few margin-oblique faults (e.g., the Overgangshytta fault) may have mildly reactivated as oblique thrusts during transpression–contraction, but shallow-dipping, bedding-parallel, duplex-shaped décollements in shales of the Billefjorden Group possibly prevented substantial movement along these faults.

scholarly journals From widespread Mississippian to localized Pennsylvanian extension in central Spitsbergen, Svalbard

2018 ◽  
Author(s):  
Jean-Baptiste P. Koehl ◽  
Jhon M. Munoz-Barrera
Keyword(s):  
Hanging Wall ◽  
Sedimentary Rocks ◽  
Normal Faults ◽  
Growth Strata ◽  
Initiation Phase ◽  
Tectonic Events ◽  
Basement Rocks ◽  
Field Evidence ◽  
Major Fault ◽  
History Of

Abstract. In the Devonian–Carboniferous, a rapid succession of clustered extensional and contractional tectonic events is thought to have affected sedimentary rocks in central Spitsbergen. These events include Caledonian post-orogenic extensional collapse associated with the formation of thick Early–Middle Devonian basins, Late Devonian–Mississippian Ellesmerian contraction, and Early–Middle Pennsylvanian rifting, which resulted in the deposition of thick sedimentary units in Carboniferous basins like the Billefjorden Trough. The clustering of these varied tectonic settings makes it sometimes difficult to resolve the tectono-sedimentary history of individual stratigraphic units. Notably, the context of deposition of Mississippian clastic and coal-bearing sedimentary rocks of the Billefjorden Group is still debated, especially in central Spitsbergen. We present field evidence from the northern part of the Billefjorden Trough, in Odellfjellet (Austfjorden), suggesting that tilted Mississippian sedimentary strata of the Billefjorden Group deposited during active (Late/latest?) Mississippian extension. Evidence include slickenside lineations and growth strata in the hanging wall of basin-oblique NNE-dipping faults, such as the Overgangshytta fault. These basin-oblique faults systematically die out upwards within Mississippian to lowermost Pennsylvanian strata and suggest a period of widespread WNW–ESE-directed extension in the Mississippian (rift “initiation” phase), followed by an episode of more localized extension in Early–Middle Pennsylvanian times (“interaction and linkage” and “through-going fault” phases). In addition, the presence of abundant basin-oblique faults parallel to the Overgangshytta fault in basement rocks adjacent to the Billefjorden Trough suggests that the formation of Mississippian normal faults was partly controlled by reactivation of preexisting Neoproterozoic (Timanian?) basement-seated fault zones. We propose that these existing faults reactivated as transverse fault or accommodation cross faults in or near the crest of transverse folds reflecting differential displacement along the Billefjorden Fault Zone, thus suggesting that normal faulting along this major fault initiated as early as the Mississippian. In Cenozoic times, the Overgangshytta fault may have mildly reactivated as an oblique thrust during transpression–contraction, and shallow-dipping bedding-parallel duplex-shaped decollements in shales of the Billefjorden Group possibly prevented further movement along Mississippian margin-oblique faults.

Geochronology of the Belt Series, Montana

1968 ◽  
Vol 5 (3) ◽  
pp. 737-747 ◽  
Author(s):  
J. D. Obradovich ◽  
Z. E. Peterman
Keyword(s):  
Average Rate ◽  
Sedimentary Rocks ◽  
Time Interval ◽  
Depositional History ◽  
Middle Cambrian ◽  
Basement Rocks ◽  
Field Evidence ◽  
Minimum Age ◽  
History Of ◽  
Central Montana

This paper presents new radiometric data that permit some qualified statements to be made on the depositional history of the Belt sedimentary rocks. The period of deposition of sedimentary rocks of the Precambrian Belt Series has been placed within a broad time interval, for they rest on metamorphosed basement rock dated at ~ 1800 m.y. and are overlain by the Middle Cambrian Flathead Quartzite (circa 530 m.y.). Prior geochronometric data gathered during the last decade indicate most of the Belt Series to be older than ~ 1100 m.y.K–Ar and Rb–Sr techniques have been applied recently to a variety of samples selected from the whole gamut of the Belt Series. Glauconite from various formations in the sequence McNamara Formation down to the uppermost beds of the Empire Formation in the Sun River area has been dated at 1080 ± 27 m.y. by the K–Ar method and at 1095 ± 22 m.y. by the Rb–Sr mineral isochron method. A Rb–Sr whole-rock isochron based on argillaceous sedimentary rocks from this 5000-ft section gives an age of 1100 ± 53 m.y. The concordance of the preceding results and the K–Ar ages (1075 to 1110 m.y.) on Purcell sills and lava imply that this age represents the time of sedimentation of these units.A Rb–Sr isochron based on whole-rock samples stratigraphically far below the Umpire Formation— the Greyson Shale, Newland Limestone, Chamberlain Shale, and Neihart Quartzite in the Big Belt and Little Beit Mountains—yields an age of 1325 ± 15 m.y. This result is interpreted as indicating a substantial unconformity beneath the Belt Series, at least in central Montana; it also suggests a major hiatus, unsuspected from field evidence, between the uppermost part of the Empire Formation and the Greyson Shale.The results for the youngest of Belt rocks—the Pilcher Quartzite and the Garnet Range Formation, which are exposed in the Alberton region—are equivocal in that there is widespread dispersion. A large component of detrital muscovite in some of the samples could readily account for the magnitude and sense of this dispersion. A maximum age of ~930 m.y. based on an isochron of minimum slope through the various points may be inferred for this sequence. A K–Ar age of 760 m.y. obtained on biotite from a sill in the Garnet Range Formation provides a minimum age for these younger Belt rocks.Three distinct periods of sedimentation for Belt rocks sampled are suggested at ≥ 1300, 1100, and ≤ 900 m.y., with two substantial hiatuses of 200 m.y. or more. In addition the data for the sequence in the Big and Little Belt Mountains suggest that sedimentation may not have commenced for a period of possibly 400 m.y. after the metamorphism that affected basement rocks, while the data for the Garnet Range and Pilcher sequence suggest that sedimentation ceased some 200 to 400 m.y. prior to the deposition of the Middle Cambrian Flathead Quartzite.To suggest that the Belt sediments were deposited continuously over a period of 400 m.y. or more would imply an unusually low average rate of deposition of ≤ 0.1 ft/1000 yr, and this for the thickest part of the Belt Series. As a realistic expression of the depositional history of the Belt Series, both viewpoints are open to question, but the viewpoint that the Belt basin has been characterized by discontinuous sedimentation would be more in keeping with the principle of uniformity.

scholarly journals Devonian–Mississippian collapse and core complex exhumation, and partial decoupling and partitioning of Eurekan deformation as alternatives to the Ellesmerian Orogeny in Spitsbergen

2020 ◽  
Author(s):  
Jean-Baptiste P. Koehl
Keyword(s):  
Fault Zone ◽  
Seismic Data ◽  
Lower Devonian ◽  
Hanging Wall ◽  
Sedimentary Rocks ◽  
Late Devonian ◽  
Strain Partitioning ◽  
Core Complex ◽  
Basement Rocks ◽  
Proterozoic Basement

Abstract. In the Late Devonian, Svalbard was affected by a short-lived episode of contraction called the Ellesmerian (Svalbardian) Orogeny, which resulted in top-west thrusting of Proterozoic basement rocks onto Devonian sedimentary strata along the Balliolbreen Fault, a major fault segment of the east-dipping Billefjorden Fault Zone, and juxtaposition of undeformed Mississippian–Permian strata against intensely folded Devonian rocks. The present study of field and seismic data shows that backward-dipping duplexes comprised of phyllitic coal and bedding-parallel décollements and thrusts localized along lithological transitions in thickened uppermost Devonian–Mississippian coals and coaly shales of the Billefjorden Group partially decoupled uppermost Devonian–Permian sedimentary rocks of the Billefjorden and Gipsdalen groups from Devonian rocks during Cenozoic contraction–transpression. In addition, Devonian strata probably experienced syn-depositional, post-Caledonian, extensional, detachment-related folding. Seismic data in Sassenfjorden and Reindalspasset show the presence of Cenozoic duplexes and bedding-parallel décollements within Lower–Middle Devonian, uppermost Devonian–Mississippian and uppermost Pennsylvanian–lowermost Permian sedimentary strata of the Wood Bay and/or Widje Bay and/or Grey Hoek formations, of the Billefjorden Group and of the Wördiekammen Formation respectively, which further decoupled stratigraphic units during Eurekan deformation. Bedding-parallel décollements and thrusts are possibly related to shortcut faulting, a roof décollement of a fault-bend hanging wall (or ramp) anticline, an imbricate fan, antiformal thrust stacks and/or fault-propagation folds over reactivated/overprinted basement-seated faults. Seismic data in Reindalspasset also indicate that Devonian sedimentary rocks might have deposited east of the Billefjorden Fault Zone, thus ruling out Late Devonian reverse movement along the Billefjorden Fault Zone in this area. Based on the present findings, juxtaposition of Proterozoic basement rocks against Lower Devonian sedimentary rocks along the Balliolbreen Fault in central Spitsbergen (e.g., Pyramiden–Odellfjellet) may be explained by down-east Carboniferous normal faulting with associated footwall rotation and exhumation and subsequent top-west Cenozoic thrusting along the Billefjorden Fault Zone. The uncertain relationship of the Balliolbreen Fault with uppermost Devonian–Mississippian sedimentary strata, the poorly constrained nature of the contact (unconformity or bedding-parallel décollements and thrusts?) between Lower Devonian and uppermost Devonian–Mississippian sedimentary strata, and along strike variations in cross-section geometry, offset stratigraphy, and inferred timing and kinematics along the Balliolbreen Fault suggest that this fault consists of several, discrete, unconnected (soft-linked and/or stepping) or, most probably, offset fault segments that were reactivated/overprinted with varying degree during Eurekan deformation due to strain partitioning. Finally, recent evidence for Devonian core complex exhumation and reinterpretation of presumed Ellesmerian structures and of Late Devonian amphibolite facies metamorphism suggest that Ellesmerian contraction is not necessary to explain fault geometries and (differential) deformation within Devonian–Permian sedimentary strata in Spitsbergen.

scholarly journals Influence of basement heterogeneity on the architecture of low subsidence rate Paleozoic intracratonic basins (Reggane, Ahnet, Mouydir and Illizi basins, Hoggar Massif)

Solid Earth ◽  
2018 ◽  
Vol 9 (6) ◽  
pp. 1239-1275 ◽  
Author(s):  
Paul Perron ◽  
Michel Guiraud ◽  
Emmanuelle Vennin ◽  
Isabelle Moretti ◽  
Éric Portier ◽  
...  
Keyword(s):  
Shear Zones ◽  
Normal Faults ◽  
Late Devonian ◽  
North African ◽  
Subsidence Rate ◽  
Tectonic Events ◽  
Structural Framework ◽  
Local Inversion ◽  
Thickness Variations ◽  
Facies Succession

Abstract. The Paleozoic intracratonic North African Platform is characterized by an association of arches (ridges, domes, swells, or paleo-highs) and low subsidence rate syncline basins of different wavelengths (75–620 km). The Reggane, Ahnet, Mouydir and Illizi basins are successively delimited from east to west by the Amguid El Biod, Arak-Foum Belrem, and Azzel Matti arches. Through the analysis of new unpublished geological data (i.e., satellite images, well logs, seismic lines), the deposits associated with these arches and syncline basins exhibit thickness variations and facies changes ranging from continental to marine environments. The arches are characterized by thin amalgamated deposits with condensed and erosional surfaces, whereas the syncline basins exhibit thicker and well-preserved successions. In addition, the vertical facies succession evolves from thin Silurian to Givetian deposits into thick Upper Devonian sediments. Synsedimentary structures and major unconformities are related to several tectonic events such as the Cambrian–Ordovician extension, the Ordovician–Silurian glacial rebound, the Silurian–Devonian Caledonian extension/compression, the late Devonian extension/compression, and the Hercynian compression. Locally, deformation is characterized by near-vertical planar normal faults responsible for horst and graben structuring associated with folding during the Cambrian–Ordovician–Silurian period. These structures may have been inverted or reactivated during the Devonian (i.e., Caledonian, Mid–Late Devonian) compression and the Carboniferous (i.e., pre-Hercynian to Hercynian). Additionally, basement characterization from geological and geophysics data (aeromagnetic and gravity maps), shows an interesting age-dependent zonation of the terranes which are bounded by mega-shear zones within the arches–basins framework. The old terranes are situated under arches while the young terranes are located under the basins depocenter. This structural framework results from the accretion of Archean and Proterozoic terranes inherited from former orogeny (e.g., Pan-African orogeny 900–520 Ma). Therefore, the sedimentary infilling pattern and the nature of deformation result from the repeated slow Paleozoic reactivation of Precambrian terranes bounded by subvertical lithospheric fault systems. Alternating periods of tectonic quiescence and low-rate subsidence acceleration associated with extension and local inversion tectonics correspond to a succession of Paleozoic geodynamic events (i.e., far-field orogenic belt, glaciation).

Was Zechstein basin in Poland just large “hole in the ground”? – new extensional model based on reinterpreted regional seismic data

2020 ◽  
Author(s):  
Piotr Krzywiec ◽  
Tadeusz M. Peryt ◽  
Hubert Kiersnowski
Keyword(s):  
Late Cretaceous ◽  
Seismic Data ◽  
Sedimentary Cover ◽  
Fault Zones ◽  
Normal Faults ◽  
Reverse Fault ◽  
Growth Strata ◽  
Thickness Increase ◽  
Central European Basin ◽  
Axial Part

<p>Syntectonic growth strata in extensional settings are characterized by gross divergent geometries towards the master normal faults. Similar depositional patterns might be expected for evaporitic successions deposited during active extension although for salt-rich systems it might be very difficult to discern initial syn-tectonic depositional thickness variations from those caused by syn-depositional or early post-depositional halokinetic flow. Evaporites can be also passively infilling accommodation space that was created before their deposition either by tectonics or by erosion. Re-evaluation of regional coverage of seismic data from the Polish Basin provided evidences that, contrary to previous views, formation of Zechstein (Wuchiapingian – Changshingian) evaporites was significantly controlled by active extension. This sedimentary basin was located within the eastern periphery of the large epicontinental Permian-Mesozoic Central European Basin System and was filled with several kilometers of siliciclastics and carbonates, and thick Zechstein evaporites. Its axial part, the Mid-Polish Trough, characterized by the thickest Permo-Mesozoic sedimentary cover and developed partly above the Teisseyre–Tornquist Zone, underwent substantial Late Cretaceous–Paleogene inversion and currently forms a large regional anticlinal structure referred to as the Mid-Polish Swell. Some previous models of deposition of Zechstein evaporites assumed that evaporation started after catastrophic flooding of vast paleo-topographic depression (“hole in the ground” model). Regional coverage of seismic data was used to map major sub-Zechstein fault network that were responsible for crustal extension during development of the Polish Basin and were reactivated as reverse fault zones during its regional Late Cretaceous – Paleogene inversion. Those sub-Zechstein fault zones are often associated with locally increased thickness of Zechstein evaporites (salt pillows). It could be shown that such thickness increase could be in turn associated with gradual thickness increase of particular Zechstein cyclothems towards sub-Zechstein fault zones. All those observations were used to construct regional model of the Zechstein basin that was controlled by regional extension. As a consequence, Zechstein evaporites deposited within the axial part of the basin have been partly reinterpreted as growth strata related to active basement extensional tectonics.</p>

scholarly journals Tectonic Evolution of the SE West Siberian Basin (Russia): Evidence from Apatite Fission Track Thermochronology of Its Exposed Crystalline Basement

Minerals ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 604
Author(s):  
Evgeny V. Vetrov ◽  
Johan De Grave ◽  
Natalia I. Vetrova ◽  
Fedor I. Zhimulev ◽  
Simon Nachtergaele ◽  
...  
Keyword(s):  
Tectonic Evolution ◽  
Fission Track ◽  
Analytical Data ◽  
Tectonic Activity ◽  
Apatite Fission Track ◽  
Tectonic Processes ◽  
Basement Rocks ◽  
Fission Track Thermochronology ◽  
History Of ◽  
West Siberian Basin

The West Siberian Basin (WSB) is one of the largest intracratonic Meso-Cenozoic basins in the world. Its evolution has been studied over the recent decades; however, some fundamental questions regarding the tectonic evolution of the WSB remain unresolved or unconfirmed by analytical data. A complete understanding of the evolution of the WSB during the Mesozoic and Cenozoic eras requires insights into the cooling history of the basement rocks as determined by low-temperature thermochronometry. We presented an apatite fission track (AFT) thermochronology study on the exposed parts of the WSB basement in order to distinguish tectonic activation episodes in an absolute timeframe. AFT dating of thirteen basement samples mainly yielded Cretaceous cooling ages and mean track lengths varied between 12.8 and 14.5 μm. Thermal history modeling based on the AFT data demonstrates several Mesozoic and Cenozoic intracontinental tectonic reactivation episodes affected the WSB basement. We interpreted the episodes of tectonic activity accompanied by the WSB basement exhumation as a far-field effect from tectonic processes acting on the southern and eastern boundaries of Eurasia during the Mesozoic–Cenozoic eras.

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