Time-Series Analysis of Crustal Deformation on Longstanding Transcurrent Fault: Structural Diversity along Median Tectonic Line, Southwest Japan, and Tectonic Implications

The Median Tectonic Line (MTL) along the longstanding convergent margin of eastern Eurasia has been activated intermittently since ca. 100 Ma. In its incipient phase, propagating strike slips on the MTL generated an elongate pull-apart depression buried by voluminous clastics of the Late Cretaceous Izumi Group. In this study, the complicated deformation processes around this regional arc-bisecting fault are unraveled through a series of quantitative analyses. Our geological survey of the Izumi Group was exclusively conducted in an area of diverse fault morphology, such as jogs and steps. The phase stripping method was introduced to elucidate the time sequence of cumulative tectonic events. After stripping away the initial structure related to basin formation, neotectonic signatures were successfully categorized into discrete clusters originating from progressive wrenching near the active MTL fault system, which has been reactivated by the Quaternary oblique subduction of the Philippine Sea Plate. The method presented here is simple and effective for the detection and evaluation of active crustal failures in mobile belts where records of multiphase architectural buildup coexist.

Normal Faulting and Volcanism in the Kora 3D Seismic Volume

<p>The spatial and temporal relationship between normal faulting and volcanism in offshore Western North Island, New Zealand can be used to gain insight into basin formation, hydrocarbon resources, regional tectonics, and large subduction processes. It is hypothesised that there is a causal relationship between volcanic activity and faulting, however, within the Taranaki Kora 3D seismic volume (survey) this relationship has not yet been explored. The overall aim of this thesis was to map and identify whether there is a relationship between volcanism and normal faulting within the Kora 3D survey. A causal relationship in location and timing between volcanic processes and fault activity was discovered in this study. Two novel models were created to explain the creation of the local stress leading to this causal relationship. The first model uses intrusive magma build up and the second extrusive cone building to explain the changes in local stress. These models not only support the causal relationship between volcanism and faulting activity but also provide a new understanding into how Kora volcanic cone activity may have influenced active faulting in the Kora 3D survey. Application of this new information will allow innovative insights into basin formation, regional and local tectonics, and subducting plate geometry in the Taranaki Basin. This research could be utilized to increase knowledge for prospecting and reduce geologic uncertainty, which is of importance for the New Zealand petroleum industry at this northern end of the Taranaki Basin.</p>

Normal Faulting and Volcanism in the Kora 3D Seismic Volume

<p>The spatial and temporal relationship between normal faulting and volcanism in offshore Western North Island, New Zealand can be used to gain insight into basin formation, hydrocarbon resources, regional tectonics, and large subduction processes. It is hypothesised that there is a causal relationship between volcanic activity and faulting, however, within the Taranaki Kora 3D seismic volume (survey) this relationship has not yet been explored. The overall aim of this thesis was to map and identify whether there is a relationship between volcanism and normal faulting within the Kora 3D survey. A causal relationship in location and timing between volcanic processes and fault activity was discovered in this study. Two novel models were created to explain the creation of the local stress leading to this causal relationship. The first model uses intrusive magma build up and the second extrusive cone building to explain the changes in local stress. These models not only support the causal relationship between volcanism and faulting activity but also provide a new understanding into how Kora volcanic cone activity may have influenced active faulting in the Kora 3D survey. Application of this new information will allow innovative insights into basin formation, regional and local tectonics, and subducting plate geometry in the Taranaki Basin. This research could be utilized to increase knowledge for prospecting and reduce geologic uncertainty, which is of importance for the New Zealand petroleum industry at this northern end of the Taranaki Basin.</p>

Basin evolution in response to flat subduction in the Altiplano

This contribution assesses models for basin formation in the Altiplano. New magnetostratigraphy, palynology, and 40Ar/39Ar and U-Pb geochronology from the central Corque Syncline demonstrate that the 7.4 km-thick section was deposited between 36.7 and 18.7 Ma. The base of the section post-dates exhumation in both the Western and Eastern cordilleras, precluding deposition in a classic retroarc foreland basin setting. Rotated paleomagnetic vectors indicate counterclockwise rotation of 0.8°/Myr since the early Oligocene. Detrital zircon provenance data confirm previous interpretations of Eocene–early Oligocene derivation from the Western Cordillera and a subsequent switch to an Eastern Cordilleran source. Flexural modeling indicates that loads consistent with paleoelevation estimates cannot account for all subsidence. Rather, the timing and magnitude of subsidence is consistent with Eocene emplacement and Oligocene–early Miocene resteepening of a flat slab. Integration of the magmatic, basin, and deformation history provides a coherent model of the effects of flat subduction on the overriding plate. In this model flat subduction controlled basin formation in the upper plate, with subsidence enhanced in front of the zone of flat subduction but reduced over the crest of the flat slab. We conclude that the Altiplano was conditioned for plateau formation by Eocene–Oligocene flat subduction.Thematic collection: This article is part of the Fold-and-thrust belts collection available at: https://www.lyellcollection.org/cc/fold-and-thrust-beltsSupplementary material:https://doi.org/10.6084/m9.figshare.c.5664345

New Perspectives on the Stratigraphy of the Andaman Trough, offshore North Sumatra, Indonesia. Utilising Modern Quantitative Biostratigraphical Analysis, Integrated with Newly Acquired 3D Multi Client Seismic Data

The Andaman Trough, located offshore North Sumatra is currently defined as an emerging basin for exploration. Its location primarily in a remote deep-water environment has resulted in limited well data being acquired to date and although there has historically been abundant seismic data, imaging of pre-Miocene stratigraphy has been poor. New seismic data, including the regional PGS NSMC3D and proprietary and multi-client 2D reprocessed data, combined with high resolution biostratigraphical analysis, has enabled extrapolation of the stratigraphy from the well explored and established shelfal areas down into the deep-water areas. To establish the high-resolution stratigraphic framework, paleo-environment, and paleo-climate for the well penetrations in the Andaman Trough, re-evaluation of quantitative and semi-quantitative abundance charts based on nannofossil, micropaleontology, and palynology zonation and sequences was conducted. Integration of this updated biostratigraphic analysis with interpretation from the modern regional seismic datasets enabled the identification of and confirmation of sequence boundaries and flooding surfaces across the Andaman Trough. Insights into timing of rifting, uplift, and erosion were made, as well as an interpretation of depositional environments, paleo-bathymetry and paleo-climate throughout the Andaman Trough. Significant findings include the chronostratigraphic separation of Late Oligocene Parapat fluvialtile deposits from the overlying Bampo marine turbidites, absent or incomplete Bampo Formation penetrated by some wells, as well as the delineation of a previously unidentified Eocene unconformity and revised timing of basin formation. Further insights into source rock development for the Eocene stratigraphic package were also developed.

Lower Cambrian (Series 2) small shelly fossils from along Nares Strait (Nunavut and Greenland; Laurentia)

Three small assemblages of lower Cambrian (Cambrian Series 2, Stage 4) small shelly fossils are described from Laurentian strata astride Nares Strait. The fauna from the Humboldt Formation of Daugaard-Jensen Land, North Greenland, is derived from inner shelf sediments deposited on the stable craton of the Inglefield Land High. Fossils from Judge Daly Promontory, eastern Ellesmere Island, Nunavut, occur in strata of the Cambrian Ellesmere Group (Kane Basin Formation) that have been structurally juxtaposed against older strata; they were originally assigned to the Kennedy Channel Formation, which is now considered to be of Neoproterozoic age. A similar fauna from offshore environments of the Aftenstjernesø Formation in northern Nyeboe Land, North Greenland, reflects the regional structural and sedimentological continuity with the Canadian Cambrian succession. Pojetaia robsonae sp. nov. is described from Judge Daly Promontory.

Timing and nature of intracontinental deformation at the northwestern margin of the Sichuan Basin, China: evidence from structural analysis and detrital zircon U–Pb ages

The theory of plate tectonics suggests that deformation occurs mainly along plate boundaries; however, compression can result in the formation of orogens and basins within intracontinental settings. During these two tectonic processes, the sedimentation and environmental changes occur in response to marginal and intracontinental deformation. Early Jurassic – Early Cretaceous deformation and basin formation along the Qinling orogenic belt and the northwestern Sichuan Basin in central–SW China are ideal for investigating a reactivated tectonic belt and basin formation. We studied the Lower Jurassic – Lower Cretaceous sedimentary sequences and structures along the northwestern margin of the Sichuan Basin, and obtained detrital zircon U–Pb ages for these rocks. The structures show that deformation migrated SE-wards and S-wards into the Sichuan Basin along the Longmen Shan, Micang Shan and Daba Shan tectonic belts during middle–late Mesozoic time. The Lower Jurassic oligomictic conglomerates have a smaller grain size and thicken towards the south, indicating protracted transport from a northern source. The conglomerates deposited near-source record post-orogenic south-vergent thrusting during the Late Triassic – Early Jurassic epochs. The Lower Cretaceous conglomerates and sandstones have multiple sources, which indicate that they were rapidly deposited near their source, synchronous with thrusting that occurred in response to coeval SE-wards and S-wards thrusting in the Longmen Shan and Daba Shan tectonic belts during the Late Jurassic – Early Cretaceous epochs. Detrital zircon grains from the Lower Jurassic – Lower Cretaceous sedimentary rocks yielded age peaks of 2600–2200, 1850–1600, 850–700, 540–400, 250–180 and 180–140 Ma. A comparison of these ages with those of surrounding exposed rocks indicates that the sediments in the northwestern Sichuan Basin were supplied from the Qinling orogenic belt, the northwestern Yangtze Block, the south margin of the North China Block and the Songpan–Garzê Terrane. The youngest peaks of detrital zircon U–Pb ages at 207 and 159 Ma constrain the two stages of intracontinental shortening and highlight the link between intracontinental deformation and sedimentation.