Extensional Subsidence Research Articles

Linking environmental changes and organic matter enrichment in the middle part of the Yanchang Formation (Ordos Basin, China) to the rollback of an oceanic slab in the eastern Paleo-Tethys

The Yanchang Formation, which records the whole evolutionary history of the Middle–Late Triassic lacustrine basin in the western part of the North China Block, provides an opportunity to understand the relationship between the tectono-sedimentary evolution and massive organic matter burial in lacustrine systems. The present study investigates the changes in the lithofacies association, provenance, regional tectonism, depositional environment, and organic matter accumulation in the lower-middle part of the Yanchang Formation, aiming to unravel their links. As a result of the rapid deepening of the southern Ordos Basin, the deposits in the depocenter of the basin shifted dramatically from shallow lacustrine sandstones of the lower part of the Yanchang Formation (i.e., Chang 8 Member) to deep lacustrine shales and gravity flow deposits of the middle part of the Yanchang Formation (i.e., Chang 7 Member). The provenance of the overlying Chang 7 Member is distinct from that of the underlying Chang 8 Member. It is proposed that crustal extension caused by the southwestward rollback of an oceanic slab in the eastern Paleo-Tethys may have triggered the rapid extensional subsidence in the southern Ordos Basin during the early Ladinian. In response to this deep geodynamic process, the depositional environment of the contemporaneous Ordos Basin changed significantly, as reflected by improved primary productivity, enhanced bottom-water anoxia, as well as reduced terrigenous clastic supply in the Ordos Lake. The coupling of these processes further led to the enrichment of organic matter in the Chang 7 Member.

The Current Crustal Vertical Deformation Features of the Sichuan–Yunnan Region Constrained by Fusing the Leveling Data with the GNSS Data

This study uses the least squares collocation method to fuse the leveling vertical deformation velocity in the Sichuan–Yunnan region with the GNSS observations of this region from 320 stations in the China Crustal Movement Observation Network (CMONOC) and the China Continental Tectonic Environment Monitoring Network (CMTEMN) from 1999 to 2017. Such fusion is to improve the accuracy of the vertical deformation rates in large spatial scales. The fused vertical deformation results show that: (1) the fused deformation field has a uniform spatial distribution, and shows detailed change characteristics of key regions; (2) the current vertical crustal motion in this region is featured by the contemporaneous occurrence of crustal compression, shortening and uplift and basin extensional subsidence; (3) most areas in this region experience uplifts, as the lateral push of the Qinghai–Tibet Plateau was blocked by the Sichuan Basin. The areas on the northwest side of the Longmenshan fault and the Lijiang-Xiaojinhe fault are dominated by uplifts, with the velocity of 1.5 mm/a–5.5 mm/a, and the region on the southeast side has slight uplifts, with the velocity of 1.0 mm/a–1.5 mm/a; (4) many areas have high gradient vertical deformation, especially the region close to the Wenshan fault and on the two sides of the Yarlung Zangbo fault that has the value of 3.0–4.0 × 10−8/a, deserving further attention to be paid to the long-term earthquake hazards.

Chapter 5 Interpretation of the origin and evolution of the Arabian Intrashelf Basin and the development of the Dhruma Atash, Tuwaiq and Hanifa sequences

Abstract This is the first of two chapters in which the data presented in the first four chapters of this Memoir are reviewed and interpreted. A summary cross-section across the basin from the Saudi outcrop to Abu Dhabi and the Tethyan margin is used to summarize the regional setting and sequences as interpreted in this Memoir. The key points illustrated by the summary cross-section are stated and discussed in the first part of this chapter. Two different interpretations for the eastern margin of the intrashelf basin are reviewed. In the first of these interpretations, the margin with the deeper waters of the Tethys Ocean shelf is adjacent to the intrashelf basin rim in Abu Dhabi, whereas in the second, preferred in this Memoir, a broad, shallow Tethyan shelf platform (200–300 km wide) extends from the intrashelf basin rim to the Tethys continental shelf edge. The implications of Late Jurassic exposure and erosion on the adjacent Tethyan shelf are discussed. The development of the Arabian Intrashelf Basin during the Callovian–late Oxfordian (the Tuwaiq Mountain Formation, the source rock and the Hanifa intervals and associated sequences) is interpreted and discussed with illustrations, including step-by-step facies maps. The interpretation integrates depositional, eustatic and tectonic factors in the evolution of the intrashelf basin. The interpretation in this Memoir is that the Arabian Intrashelf Basin began with isostatic and extensional subsidence on top of a broad Dhruma Atash Member platform, which had largely filled the accommodation space up to the wave base and to near sea-level. It developed fully into an intrashelf basin during the deposition of the Callovian Tuwaiq sequence, with rising sea-levels coincident with a productive shallow water carbonate factory resulting in a rim of shallow water carbonate. An end-Callovian to early Oxfordian lowstand terminated the Tuwaiq sequence on the basin rim. During the lowstand, restricted conditions in the basin deposited the rich Lower Hanifa source rock as a lowstand systems tract. As more normal conditions returned in a subsequent sequence, the source rock facies graded upwards into Hanifa reservoir facies, which partially filled the basin. Hanifa progradation was terminated by another lowstand during which a subaqueous gypsum/anhydrite marker bed was deposited in at least part of the remnant basin. Earlier interpretations of these sequences are also discussed.

Stratigraphic comparisons along the Pontides (Turkey) based on new nannoplankton age determinations in the Eastern Pontides: geodynamic implications

Abstract We compared the stratigraphic formations along the southern margin of the Black Sea using 196 nannoplankton ages determined in the Western and Central Pontides and 112 new samples from the Eastern Pontides. We inferred that the İstanbul and Sakarya zones were amalgamated prior to the Early Cretaceous. Extensional subsidence migrated eastwards along the Pontides from the Barremian to the Paleocene. The eastwards younging of the Cretaceous magmatism suggested that the eastern Black Sea Basin is younger. Locally, angular unconformities and a stratigraphic gap testify to the Late Albian uplift of the Central Pontides as a consequence of the collision of an oceanic edifice. Cretaceous Oceanic Red Beds are marker beds of Santonian age along the much of the Pontides and are of mainly Campanian age within the Eastern Pontides. The Middle Campanian–Paleocene was a non-volcanic period characterized by extensional subsidence mainly along the eastern Black Sea Basin. The end of Cretaceous volcanism can be correlated with a southwards subduction jump. Syn-compressional basins show that contraction started during the Ypresian along the entire Pontide belt. Eocene volcanism started earlier in the north (Lutetian) than in the south (Bartonian) of the Eastern Pontides. This propagation of syn-collisional volcanism could have resulted from slab steepening under the Eastern Pontides.

Cross-sectional anatomy and geodynamic evolution of the Central Pontide orogenic belt (northern Turkey)

Geophysical data allowed the construction of a ~250-km-long lithospheric-scale balanced cross section of the southern Black Sea margin (Espurt et al. in Lithosphere 6:26–34, 2014). In this paper, we combine structural field data, stratigraphic data, and fault kinematics analyses with the 70-km-long onshore part of the section to reconstruct the geodynamic evolution of the Central Pontide orogen. These data reveal new aspects of the structural evolution of the Pontides since the Early Cretaceous. The Central Pontides is a doubly vergent orogenic wedge that results from the inversion of normal faults. Extensional subsidence occurred with an ENE-trend from Aptian to Paleocene. We infer that the Black Sea back-arc basin also opened during this period, which was also the period of subduction of the Tethys Ocean below the Pontides. As in the Western Pontides, the Cretaceous–Paleocene subsidence was interrupted from Latest Albian to Coniacian time by uplift and erosion that was probably related to a block collision and accretion in the subduction zone. The restoration of the section to its pre-shortening state (Paleocene) shows that fault-related subsidence locally reached 3600 m within the forearc basin. Structural inversion occurred from Early Eocene to Mid-Miocene as a result of collision and indentation of the Pontides by the Kirsehir continental block to the south, with 27.5 km (~28 %) shortening along the section studied. The inversion was characterized by NNE-trending shortening that predated the Late Neogene dextral escape of Anatolia along the North Anatolian Fault and the modern stress field characterized by NW-trending compression within the Eocene Boyabat basin.

Episodic subsidence and active deformation of the forearc slope along the Japan Trench near the epicenter of the 2011 Tohoku Earthquake

To investigate the present-day geological deformation occurring off the Pacific coast of Tohoku, Japan, we obtained high-resolution multichannel seismic reflection and bathymetric data in 2007. The study area is located along the Japan Trench near the epicenter of the 2011 off the Pacific coast of Tohoku Earthquake. The seismic profiles do not show active structures indicative of compressional stress on the forearc slope. Instead, recent tectonic deformation is characterized by extensional subsidence and the occurrence of normal faults within a series of small basins on the slope to a water depth of ∼3000 m. These isolated basins are thickest (∼525 m, ∼0.7 s two-way travel time) in regions underlying areas of flat bathymetry. The isolated basins range in width from several to 40 km and are covered by stratified sediments onlapping at the termination of concave-down reflectors. The seismic units below the basins show continuous, subparallel internal reflectors, suggesting that the subsidence-related deformation started abruptly and recently. The thickness of sediments overlying the unconformity at the top of the Cretaceous is roughly constant in the upper slope area. However, lenticular internal reflection patterns occur locally. The lenticular sedimentary units are similar to the isolated basins in terms of their widths and internal reflection patterns. We infer that episodes of extensional deformation of the overriding plate, in the form of isolated basins, have occurred over geological time. We suggest that the geological structures of the forearc slope along the Japan Trench are typical of those resulting from subduction erosion and propose that the episodic subsidence accompanied by normal faulting is the most recent deformation.

The Lower Permian Wasp Head Formation, Sydney Basin: high‐latitude, shallow marine sedimentation following the late Asselian to early Sakmarian glacial event in eastern Australia

AbstractThe Lower Permian Wasp Head Formation (early to middle Sakmarian) is a ∼95 m thick unit that was deposited during the transition to a non‐glacial period following the late Asselian to early Sakmarian glacial event in eastern Australia. This shallow marine, sandstone‐dominated unit can be subdivided into six facies associations. (i) The marine sediment gravity flow facies association consists of breccias and conglomerates deposited in upper shoreface water depths. (ii) Upper shoreface deposits consist of cross‐stratified, conglomeratic sandstones with an impoverished expression of the Skolithos Ichnofacies. (iii) Middle shoreface deposits consist of hummocky cross‐stratified sandstones with a trace fossil assemblage that represents the Skolithos Ichnofacies. (iv) Lower shoreface deposits are similar to middle shoreface deposits, but contain more pervasive bioturbation and a distal expression of the Skolithos Ichnofacies to a proximal expression of the Cruziana Ichnofacies. (v) Delta‐influenced, lower shoreface‐offshore transition deposits are distinguished by sparsely bioturbated carbonaceous mudstone drapes within a variety of shoreface and offshore deposits. Trace fossil assemblages represent distal expressions of the Skolithos Ichnofacies to stressed, proximal expressions of the Cruziana Ichnofacies. Impoverished trace fossil assemblages record variable and episodic environmental stresses possibly caused by fluctuations in sedimentation rates, substrate consistencies, salinity, oxygen levels, turbidity and other physio‐chemical stresses characteristic of deltaic conditions. (vi) The offshore transition‐offshore facies association consists of mudstone and admixed sandstone and mudstone with pervasive bioturbation and an archetypal to distal expression of the Cruziana Ichnofacies. The lowermost ∼50 m of the formation consists of a single deepening upward cycle formed as the basin transitioned from glacioisostatic rebound following the Asselian to early Sakmarian glacial to a regime dominated by regional extensional subsidence without significant glacial influence. The upper ∼45 m of the formation can be subdivided into three shallowing upward cycles (parasequences) that formed in the aftermath of rapid, possibly glacioeustatic, rises in relative sea‐level or due to autocyclic progradation patterns. The shift to a parasequence‐dominated architecture and progressive decrease in ice‐rafted debris upwards through the succession records the release from glacioisostatic rebound and amelioration of climate that accompanied the transition to broadly non‐glacial conditions.

Mesozoic evolution of the Hefei basin in eastern China: Sedimentary response to deformations in the adjacent Dabieshan and along the Tanlu fault

Research Article| July 01, 2007 Mesozoic evolution of the Hefei basin in eastern China: Sedimentary response to deformations in the adjacent Dabieshan and along the Tanlu fault Qing-Ren Meng; Qing-Ren Meng 1Department of Geology, Northwest University, Xi‘an 710069, Shaanxi, China, and Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China Search for other works by this author on: GSW Google Scholar Shuang-Ying Li; Shuang-Ying Li 2School of Resource and Environmental Engineering, Hefei University of Technology, Hefei 230009, Anhui, China Search for other works by this author on: GSW Google Scholar Ren-Wei Li Ren-Wei Li 3Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China Search for other works by this author on: GSW Google Scholar GSA Bulletin (2007) 119 (7-8): 897–916. https://doi.org/10.1130/B25931.1 Article history received: 07 Nov 2005 rev-recd: 12 Jan 2007 accepted: 28 Jan 2007 first online: 08 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Qing-Ren Meng, Shuang-Ying Li, Ren-Wei Li; Mesozoic evolution of the Hefei basin in eastern China: Sedimentary response to deformations in the adjacent Dabieshan and along the Tanlu fault. GSA Bulletin 2007;; 119 (7-8): 897–916. doi: https://doi.org/10.1130/B25931.1 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGSA Bulletin Search Advanced Search Abstract This paper presents a study of Jurassic–Early Cretaceous sedimentary evolution of the Hefei basin in eastern China and explores the relationship between clastic sedimentation and coeval deformation of the Dabieshan to the south and the Tanlu fault to the east. The Hefei basin experienced a two-stage evolution. The basin was initiated in the Early Jurassic and expanded in the Middle and Late Jurassic. The synsedimentary Jinzhai normal fault is considered to be a border fault of the basin because it controlled Middle to Upper Jurassic proximal alluvial deposits. Persistent N- to NE-directed paleo-flows in the southern Hefei basin indicate that sediments came from the Dabieshan, and the presence of Triassic coesite-bearing detrital zircon in Lower Jurassic sediments documents exhumation of ultrahigh-pressure rocks of the Dabieshan to the surface as early as the Early Jurassic. Occurrences of eclogite clasts in an Upper Jurassic unit indicate continued denudation of the Dabieshan at that time. Thickening of Jurassic clastic units to the southern and southeast parts of the basin suggests that basin subsidence and depositional loci were under the coupled control of the Jinzhai normal fault on the south and the NE-striking left-lateral transtensional Tanlu fault on the east. Jurassic extensional subsidence of the Hefei basin is in marked contrast to the coeval development of a contractional foreland basin south of the Dabieshan, which combines to indicate contemporaneous extension and contraction on the north and south sides of the Dabieshan, respectively. Vigorous volcanism and uplift of the southern Hefei basin characterized the second stage of development of the Hefei basin in the Early Cretaceous, and this led to a synchronous shift of its main depocenter to the north. This younger depocenter is characterized by lacustrine and fluvial-deltaic sedimentation, where alluvial and fan-deltaic coarse-grained deposition mainly occurred along the eastern edge of the basin. Early Cretaceous subsidence is attributed to E-W extension across the middle segment of the Tanlu fault, and the Zhangbaling massif on the east acted as a footwall and provided a source for sediment to the northern basin. A model is accordingly advanced to account for how the Hefei basin developed in response to the tectonic exhumation of the Dabieshan and the deformation of the Tanlu fault in the Mesozoic. It illustrates that the Hefei basin initiated and evolved during Jurassic time in an extensional setting that was triggered by southerly upward extrusion of ultra-high-pressure rocks of the Dabieshan. Early Cretaceous development of the basin was controlled by magmatism-related uplift of the Dabieshan on the south and orthogonal normal faulting of the middle segment of the Tanlu fault on the east. This study provides an independent constraint upon the exhumation processes of ultrahigh-pressure rocks of the Dabieshan. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

Kaapvaal craton: Changing first- and second-order controls on sea level from c. 3.0 Ga to 2.0 Ga

Well preserved supracrustal basin-fills including the oldest large depository (Witwatersrand) known makes the Kaapvaal craton an ideal example for studying controls on first- and second-order stratigraphic cyclicity. The duration of the three basins studied (Witwatersrand, Ventersdorp and Transvaal), from c. 3.0 to c. 2.0 Ga is almost twice that of the entire Phanerozoic period, from which the paradigms of classical sequence stratigraphy have been derived. Amongst these is an assumption that cyclicity at specific hierarchical levels is predictable and repetitive through Earth history. This does not appear to be borne out by the Precambrian record studied here; instead, a hierarchical order of cycles based on relative importance of sequences allied to a more flexible approach to controls on stratigraphic cyclicity at first- and second-orders is preferred. First-order cycles within the c. 3.0–2.0 Ga period on Kaapvaal are synonymous with the entire evolution of a supracrustal basin-fill defined by a specific basin-type; second-order cycles define basin-fill packages of unique character, which reflect large scale shifts in the accommodation–sedimentation balance. Early to Middle Archaean evolution of the Kaapvaal craton encompassed amalgamation of a mosaic of subdomains, to produce an early south–southeastern nucleus by c. 3.1 Ga. Accretion of composite terranes from both north and west followed from c. 3.0–2.7 Ga; this was contemporaneous with evolution of the c. 3.0–2.8 Ga Witwatersrand basin. The high-grade Limpopo terrane was amalgamated with the Kaapvaal craton between 2.95 and 2.69 Ga, although a younger age for this orogensis is also possible. The Witwatersrand first-order depositional cycle was controlled largely by subduction-related tectonic loading and had a duration of c. 190 My. The c. 5 My first-order cycle of the c. 2.7 Ga Ventersdorp basin was essentially controlled by thermal uplift-induced extensional subsidence, and that of the c. 650 My Transvaal basin by extensional and subsequent thermal subsidence. It is noteworthy in the three basins examined that first-order cycles controlled by plate tectonics (Witwatersrand and Transvaal basins) were about two orders of magnitude longer relative to the Ventersdorp “plume tectonic” cycle; second-order cycles also varied greatly, from c. 100 My to c. 1 My. Within the Witwatersrand and Transvaal basins, subsidence allowed extensive seaways to develop, within which classical sequence stratigraphic systems tracts can be recognized, reflecting different stages of shoreline shifts. Within the short-lived Ventersdorp continental basin system, sedimentological criteria can be used to discriminate high and low accommodation systems tracts. The Transvaal first-order cycle was terminated at c. 2.0 Ga by the Bushveld Complex plume event.

Neogene stratigraphy and Andean geodynamics of southern Ecuador

The present paper reviews Tertiary volcanic and sedimentary formations in the Inter-Andean region of southern Ecuador (between 2°S and 4°20′S) in order to develop a geodynamic model of the region. The formations occur in the southern shallow prolongation of the Inter-Andean Valley between the Cordillera Real to the east, and the Cordillera Occidental and Amotape–Tahuı́n Provinces to the west. One hundred fifty zircon fission-track analyses has established a detailed chronostratigraphy for the sedimentary and volcanic formations and several small intrusions. The Paleogene to early Miocene formations are dominated by intermediate and acidic volcanic and pyroclastic rocks. In addition, relics of Eocene continental sedimentary series have been identified. The Neogene sedimentary series lie unconformably on deformed and eroded metamorphic, sedimentary and volcanic formations. They were deposited in two stages, which are separated by a major unconformity dated at ≈10–9 Ma. (1) During the middle and early late Miocene (≈15–10 Ma) marginal marine deltaic, lagoonal, lacustrine and fluvial environments prevailed, which we group under the heading “Pacific Coastal sequences”. They presumably covered a greater surface area in southern Ecuador than their present occurrence in small topographic depressions. We suggest that they were deposited in the shallow marine Cuenca and Loja Embayments. Deposition in a marginal marine environment is also supported by the occurrence of brackish water ostracods and other fauna. (2) Above the regional (angular) unconformity, the coastal facies are overlain by late Miocene (≈9–5 Ma) continental alluvial fan and fluvial facies which are in turn covered by mainly airborne volcanic material. They represent the “Intermontane sequences” of the basins of Cuenca, Girón–Santa Isabel, Nabón, Loja and Malacatos–Vilcabamba. Sedimentologic and stratigraphic results are used to discuss the tectonic setting of Neogene sedimentation in the forearc and arc domain of the Ecuadorian subduction system. During the Pacific Coastal stage, northward displacement of the coastal forearc block along the Calacali–Pallatanga fault zone has driven crustal collapse in the Inter-Andean region. As a result, extensional subsidence drove the eastward ingression of shallow seas into the Cuenca and Loja Embayments from the Manabı́ and Progreso Basins to the west. Tectonic inversion in the forearc area during the early late Miocene (at ≈9.5 Ma) reflects the initiation of W–E oriented compression and uplift in the Inter-Andean region and the establishment of smaller Intermontane stage basins, which host the continental sequences. Coeval topographic rise of the Cordillera Occidental is indicated by the onset of clastic input from the west. The small Intermontane Basin of Nabón (≈8.5–7.9 Ma) formed during the period of maximum compression. The present data prove that the Neogene Andean forearc and arc area in southern Ecuador was a site of important but variable tectonic activity, which was presumably driven by the collision and coupling of the Carnegie Ridge with the Ecuadorian margin since ≈15–9 Ma.

Flexural cantilever models of extensional subsidence in the Munster Basin (SW Ireland) and Old Red Sandstone fluvial dispersal systems

Abstract Flexural cantilever (2D) computer modelling of the palinspastically restored Mid-Late Devonian Munster Basin has been used to appraise quantitatively extensional subsidence and Old Red Sandstone (ORS) stratigraphic geometries. One-dimensional decompaction and (Airy isostatic) backstripping were carried out to constrain syn-rift forward models; these specify the Late Palaeozoic rifting history of the region. Forward modelling showed that listric faults and detachments fail to reproduce restored ORS sediment geometries, but instead indicated that multiple planar, upper-crustal faults are necessary to achieve the correct order of syn-rift subsidence across the basin. Modelled (non-unique) sections transverse to the basin bounding fault (Dingle Bay-Galtree Fault Zone) replicated ORS geometries with cumulative extensions of 27 km in the east (stretching factor β = 1.3) and 59 km in the west (β = 1.48), with effective elastic thicknesses of 7 and 8 km, respectively, starting from a 40 km thick post-Acadian crust. Resultant peak heat-flow anomalies predict well the location of known syn-rift volcano-magmatic centres. Modelling indicated that significant offshore faults are required to achieve subsidence in the west Cork region, implying that the basin continues offshore. Observed ORS (<0.85 km thick) sections on the regional footwall, considered to be the result of thermal (post-rift) subsidence, are not accounted for by modelling, whereas c . 1 km of post-rift ORS is modelled over 5 Ma in the central-southern regions of the basin. These sections buried the principal rift faults during late Famennian time. The ORS of the Munster Basin is dominated by two large-scale transverse fluvial dispersal systems that were largely insensitive to deflection by any extension faults that propagated in the syn-rift fill. A third major system entered in the SW, demarcated by antithetic extension faults south of the depocentre.

Gravity anomalies, subsidence history and the tectonic evolution of the Malay and Penyu Basins (offshore Peninsula Malaysia)

To demonstrate the extensional origin of the Malay Basin and calculate the stretching factor (β), Madon & Watts (1998) conducted subsidence-history backstripping on more than 60 wells. The resulting backstripped basement depths through time were then matched to best-fit theoretical subsidence curves, suggesting a McKenzie (1978)-type basin with rapid extensional subsidence (\\\'synrift\\\') followed by slower thermal subsidence (\\\'postrift\\\'). However, the match is only \\\'relatively poor\\\' (p. 381) for the first half of the basin\\\'s 35-0 Ma history (see subsidence curves, Madon & Watts 1998, fig. 7). In the second half, the match looks better on cursory inspection of the subsidence curves, but this is partly an artefact of lacking basement-depth data points over part of this time interval (e.g. 19-0 Ma in well M-6; 7-0 Ma in all 12 illustrated wells).

Extensional subsidence, contractional folding and thrust inversion of the eastern Cameros basin, northern Spain

Tectonic analysis of the Cameros massif (northern Spain) demonstrates the need to integrate detailed structural analysis with stratigraphic studies in order to understand the development of inverted basins. The Cameros massif underwent three major tectonic events, each characterized by different mechanisms of deformation: The first event (Tithonian–Early Albian) manifested as continental rifting and formation of the Cameros basin and was attended by normal faulting and related folding of pre- and syn-rift sedimentary sequences (up to 9 km thick). It corresponded to the beginning of rifting and opening of the Bay of Biscay to the north of the massif. The second event occurred at the end of the Early Cretaceous. The basin underwent contraction, manifested as gentle folds containing axial-plane cleavage. This contraction was due to the migration of the center of rifting away from the basin and toward the northeast, and correlates with the onset of oceanic spreading in the Bay of Biscay. Deformation happened during a low-grade metamorphism period that reached its thermal peak after folding and cleavage formation (90–100 Ma). The final stage of deformation (Eocene–Miocene), following a structurally quiescent period of approximately 40 Ma, occurred during the convergence/collision between Iberia and Europe. It formed contractional folds related to large E/W-striking overthrusts. The Mesozoic basin was inverted and transported 25 km toward the north. During this stage both unfolding and tightening of the former folds occurred, as determined from analysis of cleavage orientation associated with the previous shortening.

Inverse relation between ice extent and the late Paleozoic glacial record of Gondwana

Research Article| November 01, 1995 Inverse relation between ice extent and the late Paleozoic glacial record of Gondwana Gustavo González-Bonorino; Gustavo González-Bonorino 1Glaciated Basin Research Group, Environmental Earth Sciences, University of Toronto, Scarborough, Ontario M1C 1A4, Canada Search for other works by this author on: GSW Google Scholar Nicholas Eyles Nicholas Eyles 1Glaciated Basin Research Group, Environmental Earth Sciences, University of Toronto, Scarborough, Ontario M1C 1A4, Canada Search for other works by this author on: GSW Google Scholar Author and Article Information Gustavo González-Bonorino 1Glaciated Basin Research Group, Environmental Earth Sciences, University of Toronto, Scarborough, Ontario M1C 1A4, Canada Nicholas Eyles 1Glaciated Basin Research Group, Environmental Earth Sciences, University of Toronto, Scarborough, Ontario M1C 1A4, Canada Publisher: Geological Society of America First Online: 02 Jun 2017 Online ISSN: 1943-2682 Print ISSN: 0091-7613 Geological Society of America Geology (1995) 23 (11): 1015–1018. https://doi.org/10.1130/0091-7613(1995)023<1015:IRBIEA>2.3.CO;2 Article history First Online: 02 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Gustavo González-Bonorino, Nicholas Eyles; Inverse relation between ice extent and the late Paleozoic glacial record of Gondwana. Geology 1995;; 23 (11): 1015–1018. doi: https://doi.org/10.1130/0091-7613(1995)023<1015:IRBIEA>2.3.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGeology Search Advanced Search Abstract The late Carboniferous–earliest Permian age estimate (300–280 Ma) for maximum ice volume during late Paleozoic glaciation of Gondwana is challenged. Past estimates assume a direct relation between extent of depositional glacial record and former ice cover; this assumption cannot be sustained, given that the glacial record is composed predominantly of glacially influenced marine strata that accumulated on the margins of ice-covered areas. We argue that Gondwana ice cover expanded in the Early Carboniferous in response to polar position, availability of moisture from a mediterranean sea, and epeirogenic uplift of the Gondwana interior. In Namurian time (ca. 325 Ma), Gondwana ice cover attained a maximum extent of about 21 × 106 km2, nearly the area of maximum Pleistocene ice cover. Despite extensive ice cover, the depositional record is meager; continental glacial deposits are poorly preserved on a regional unconformity. Thereafter, extensional subsidence of intracratonic basins promoted marine flooding, fragmentation of the ice cover, and the accumulation of thick glacially influenced marine deposits. In Stephanian-Asselian time (ca. 285 Ma), ice cover had decreased to about 15 × 106 km2, but glacial marine strata were being deposited and preserved across a very large area of the Gondwana supercontinent. This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

Evolution of the Southern San Joaquin Basin and mid‐Tertiary “transitional” tectonics, central California

A Cenozoic tectonic and sedimentary history is proposed for the Southern San Joaquin Basin (SSJB) and Tehachapi Mountains that evolved adjacent to the plate margin off central California. Seismic reflection, borehole, field, biostratigraphic, and paleomagnetic data are integrated into geologic and fault structure maps, cross sections, and geohistory plots and are analyzed with previous work in the region to develop a model relating the sequence, timing, and distribution of complex, tectonically linked events. The largely buried structures and strata in the SSJB preserve an unusually complete record of the mid‐Tertiary transition from convergent to transform plate boundary as well as the regional transition to contraction during the Pliocene. Significant structural relief, existing across both extensional and contractile features, is preserved in the subsurface and an active fold‐thrust belt propagates basinward along the margin of the U‐shaped Tejon embayment The Cenozoic evolution of the SSJB reflects the regional deformation of central California as different tectonic events followed each other along the adjacent North American plate margin. Five Oligocene‐Miocene basin phases are identified in the SSJB: (1) late Oligocene/early Miocene extensional subsidence, with high‐ and low‐angle normal faulting, accompanied by volcanism and deposition of coarse syntectonic conglomerates; (2) middle Miocene uplift; (3) later mid‐Miocene transtensional subsidence to lower bathyal depths; (4) alternating subsidence and uplift until the late Miocene; and (5) flexural subsidence due to Pliocene to Recent contraction. Reconstructions of mid‐Tertiary California place the southern San Joaquin/Tehachapi extensional terrane as a paleotectonic block located between the Western Mojave terrane (then to the east) and the Western California terrane (then to the south and west). Regional extension occurred during a long transition period between convergent and transform boundaries along the North American plate margin. Significant slip along the San Andreas transform postdates this extensional event. Its origin apparently coincided with a regional middle Miocene uplift event, indicating that the San Andreas fault is younger than previously supposed. The Tertiary SSJB has subsided due to extension/transtension, crustal tilting, and thrust‐related loading. The Maricopa Subbasin floor is likely composed of ensimatic and mafic rocks like those along the west side of the Sierra Nevada and locally has subsided beyond 12 km. In contrast, the relatively stable Tejon embayment, underlain by Sierran crystalline crust, achieved its maximum subsidence in the Miocene. Since Pliocene time, the SSJB has filled and continued to deepen after the basin was tectonically shut off from the Pacific Ocean.

Half‐graben lacustrine sedimentary rocks of the lower Carboniferous Strathlorne Formation, Horton Group, Cape Breton Island, Nova Scotia, Canada

ABSTRACTThe Strathlorne Formation is the middle formation of a three‐part Horton Group stratigraphy present throughout the post‐Acadian Orogeny Maritimes Basin in Atlantic Canada. It is up to 600 m in thickness and is of Tournaisian age. The formation was deposited in a complex lacustrine system during the period of maximum fault‐bounded extensional subsidence within two asymmetric half‐graben sub‐basin segments of a large rift. This rift was located at a palaeolatitude of 10–15°S. Four facies assemblages are identified and interpreted: (1) dark grey mudstone (open lacustrine), (2) grey, very fine to fine‐grained sandstone (nearshore/shoreline), (3) grey, medium‐grained sandstone to conglomerate (fan delta) and (4) red siltstone to fine‐grained sandstone (interdeltaic mudflat). Interpreted structural asymmetry of the fault‐bounded sub‐basins is evidenced by asymmetry of sediment input, facies distribution and palaeoflow in the lacustrine sedimentary fill. These indicators suggest that the sub‐basins, which were linked end‐to‐end, had opposed polarity of structural asymmetry during deposition of the Strathlorne Formation. Open lacustrine sediments are typified by stacked shallowing‐upward sequences, each representing deepening due to sub‐basin‐wide subsidence events followed by gradual infilling to shallow water depths. Sub‐basin asymmetry is also reflected in the contrast of thick sequences and grouped thinner sequences at marginal and axial positions, respectively. The lakes which occupied the sub‐basins were large (up to 100 × 50 km), tens to hundreds of metres deep and periodically stratified (presence of an anoxic hypolimnion, at least near sub‐basin axes).

Neogene to Quaternary rifting, sedimentation and uplift in the Corinth Basin,Greece

Normal faulting, regional uplift and glacio-eustacy have controlled patterns of sedimentation on a variety of scales during the active rift history of the Corinth Basin. Extensive sections through 800 m of early rift deposits are exposed in the north of the basin. These are overlain by andesites dated at 3.62 ± 0.18 and 4.00 ± 0.40 Ma. Early in the rifting process, basin relief controlled by normal faulting determined broad environmental conditions. Slope gradients determined transport process within an east-west asymmetric graben. Palaeoflow and provenance data allow lateral and axial sediment dispersal systems to be distinguished, and indicate that the Corinth basin was separated by a drainage divide from the larger Gulf of Corinth basin, to the west, during the Lower Pliocene. Sedimentary facies and thickness changes across faults, and the distribution of unconformities and soft-sediment deformation features define active tectonism at this time. As such, the Corinth Basin provides a model for the recognition of syn-rift unconformities and associated depositional patterns in other extensional basins. Since the mid-Pliocene, a combination of regional, crustal uplift and of more localized, fault-controlled, extensional subsidence have determined basin form. In the north of the basin, Lower Pliocene and Quaternary marine sediments have been uplifted up to 300 m above present-day sea-level. Normal faulting during the same episode separated successive intrabasinal depocentres from emergent highs that were subject to erosion. The competition between uplift and extensional subsidence has important implications for the back-arc evolution of the central Aegean area. The uplift suggests that crustal underplating by the subducted Mediterranean plate may have advanced as far north as northern Peloponessus and Corinth by the Upper Pliocene-Lower Pleistocene.

The Lower Carboniferous Stainmore Basin, N. England: extensional basin tectonics and sedimentation

Recently released industry seismic data image a 6 km thick Dinantian succession in the Stainmore Basin, and are used to interpret deposition in response to extensional subsidence. The basin is bounded to the north by the Lunedale–Wigglesworth–Butterknowle en echelon suite of normal faults. An early (?Courceyan–?Arundian) syn-rift sequence more than 4 km thick includes footwall-derived clastic fans. A basinal terrigenous sequence deposited through the Arundian, Holkerian and early Asbian contrasts with coeval carbonates on the Ravenstonedale Shelf and the Askrigg Block. Deposition continued in the basin whilst the Alston block and northern parts of the basin were emergent during early Asbian times. A late Asbian relative base level rise and the possible cessation of active rifting allowed both basin and structural highs to be inundated by shallow marine carbonates. Rhythmic ‘Yoredale’ sedimentation followed. Dinantian depositional patterns reflect the interplay between active extensional faulting, a suspected local inversion event, changes in sediment influx rates, sea level variations and differential rates of compaction between basement highs and the basin. However, error margins on the available biostratigraphy and timing of active faulting prevent the detailed separation of these variables and their impact on sedimentation in the Dinantian.

Tectono‐sedimentary analysis of alternate‐polarity half‐graben basin‐fill successions: Late Devonian‐Early Carboniferous Horton Group, Cape Breton Island, Nova Scotia

Abstract The Devono‐Carboniferous Horton Group of Cape Breton Island was mostly deposited in two fault‐bounded asymmetric sub‐basins which were part of a large intracontinental rift system. This system lay at a palaeolatitude of about 10–15o S–a warm, semi‐arid climate. The half‐graben sub‐basins had opposed polarity, were approximately 100 times 50 km in size and were separated by a narrow zone of elevated Acadian basement. These features are common to the adjacent structural segments of known rifts, and are unlike those of transtensive pull‐apart systems. Sedimentation occurred in four successive depositional systems which reflect a tectonic evolution of increased and then decreased extensional subsidence through the 8–12 Myr interval represented. Post‐Acadian sedimentation began with System 1 bimodal volcanics and grey distal braided fluvial sediments deposited in a slowly subsiding broad linear sag basin. System 2 consists of reddened braidplain sediments near fault‐bounded margins and mudflat/playa sediments in sub‐basin centres, deposited in two discrete asymmetric sub‐basins with a general upward‐fining trend. Gradual expansion of the mudflat setting and confinement of coarse marginal fades is interpreted as a response to increasingly rapid and deep fault‐bounded subsidence. Depositional System 3, is a complex of grey lacustrine offshore, shoreline and fan delta facies deposited in two adjacent half‐graben segments with opposed polarity of asymmetry. An increased rate of tectonic subsidence allowed a large standing body of water to accumulate lacustrine sediments along the axis of each sub‐basin during this phase of maximum subsidence. System 4 consists of reddened proximal alluvial fan, medial fluvial and distal grey meandering fluvial/floodplain sediments which accumulated in sub‐basins with fault‐bounded margins and asymmetry identical to those of earlier systems, indicating a continuation of tectonic style. However, an overall coarsening‐upward trend indicates waning of active fault‐related subsidence and consequent progradation of marginal coarse wedges to fill the sub‐basins. Rapid marine transgression and deposition of Windsor Group carbonates, evaporites and elastics continued within a more extensive rift basin during renewed fault‐bounded subsidence.

Origin of the Cambrian-Ordovician sedimentary cycles of Wisconsin using tectonic subsidence analysis

Cambrian-Ordovician stratigraphy of the Wisconsin dome is organized into five cycles consisting of basal quartzose sandstone, overlain by glauconitic sandstone and capped by limestone or dolostone. Unconformities at the base of each cycle are found to be coeval with known times of rapid tectonic subsidence in the Illinois basin at approximately 512, 502, 495, and 461 Ma. These times of rapid basin subsidence in the Illinois basin are interpreted to represent resurgent faulting events concurrent with thermal subsidence. Such regional extensional faulting would cause concomitant minor uplift of the Wisconsin dome, developing erosional unconformities observed at the base of each Cambrian-Ordovician stratigraphic cycle. Because sea level was rising at a constant global rate during deposition of the Cambrian-Ordovician cycles, stabilization of minor uplift permitted local transgression and deposition of a successive cycle. Repeated faulting during thermal subsidence in the Illinois basin caused repeated minor uplift on the Wisconsin dome, each time initiating a new stratigraphic cycle. Exceptions to this model include initial Late Cambrian transgression onto the midcontinent and a global drop in sea level at 485 Ma. The findings suggest that geodynamic models proposing a two-stage process from mechanical fault-controlled subsidence to thermal subsidence during evolution of extensional basinsmore » may need to be modified to include the occurrence of coeval extensional faulting and thermal subsidence during initial stages of basin thermal subsidence.« less