Deepest Crustal Block Research Articles

GIS-Practical Experience in the Boundaries Definition of the Platform Deep Crustal Blocks on the Studying of the Earth’s Surface Fractal Divisibility: Example of the White Sea-Kuloi Plateau

GIS-Practical Experience in the Boundaries Definition of the Platform Deep Crustal Blocks on the Studying of the Earth’s Surface Fractal Divisibility: Example of the White Sea-Kuloi Plateau

Crustal thermal regime of Ikogosi warm spring, Nigeria inferred from aeromagnetic data

Spectral analysis method was applied to aeromagnetic data obtained for Ikogosi warm spring (IWS) area of southwestern Nigeria. This was done with the objective of determining the bottom of the magnetized crust called Curie point depth (CDP) and understand the nature and extent of the local geothermal system at depth beneath IWS. The depth to the centroid, Zo, of the deepest distribution of the magnetic dipoles was obtained by computing least-squares fit to the lowest-frequency segment of the azimuthally averaged log power spectrum. The average depth to the top of the deepest crustal block was computed as the depth to the top, Zt, of the second lowest-frequency segment of the spectrum. The depth to the bottom of the deepest magnetic dipoles, the inferred Curie point depth, was then calculated from Zb = 2Zo − Zt. The Curie depth estimates for IWS range between 4.68 and 11.38 km (below sea level). We also estimate the heat flow and Curie temperature using a one-dimensional conductive heat transport model. The average heat flow, 42 mW m−2, and geothermal gradient, 32°C/km, obtained suggest a low enthalpy thermal regime. The Curie temperature for the region varies between 153°C and 350°C. Also, an inverse linear relationship between heat flow and Curie depths was determined. Good agreement between the Curie point depths derived from heat flow data and magnetic data suggests that the Curie point depth analysis is useful to estimate the regional thermal structure and the tectonic settings.

Transverse segmentation of the Baram-Balabac Basin, NW Borneo: refining the model of Borneo's tectonic evolution

The West Baram Line separates NW Borneo’s two petroleum systems. Oligocene sandstone and Lower Miocene carbonate reservoirs of the gas-prone Luconia system lie SW of that line. Northeast of the West Baram Line, the oil-rich Baram-Balabac Basin produces from Middle Miocene to Early Pliocene sandstones deposited in a foreland basin on the western side of the mountainous interior of Borneo. On the present-day shelf exploration efforts spanning nearly four decades have focused on the Champion and Baram deltas and associated extensional growth fault structures. Many of these structures have experienced youthful inversion owing to ongoing tectonic shortening. Recent discoveries prove this petroleum system extends into deep water beyond the modern shelf edge where an active fold-thrust belt has formed above autochthonous rifted continental crust of the Dangerous Grounds province in the South China Sea. New regional mapping (c. 100 000 km2) integrating seismic, borehole and gravity data shows that the Baram-Balabac Basin is segmented into four structural domains whose boundary zones trend NW-SE similar to the strike of the West Baram Line. Domain boundaries appear to control the position of the basin’s palaeoshelf edges, turbidite depositional systems, major unconformities and the position of the basin’s largest fields. These observations suggest that the domain boundaries are the expression of deep structures, probably within the underlying rifted continental crust. Two of the domain boundaries can be projected onshore to align with fault systems separating contrasting geological elements indicating they represent features of tectonic interest. The onshore geology of NW Borneo represents the early history of the Baram-Balabac Basin. The onshore geology is reviewed and new outcrop, biostratigraphic and palaeomagnetic data from Sabah are discussed in light of current models for the region’s tectonic evolution. A hybrid model is proposed in which the Baram-Balabac Basin post-dates the Sarawak Orogeny. The Sarawak Orogeny, which appears to be more regionally extensive than previously believed, is attributed to Eocene to Early Oligocene collision of the Dangerous Grounds and Reed Bank with Sabah and Palawan. In the proposed model Oligo-Miocene subduction of oceanic crust under NW Borneo is minimal. The Sabah Orogeny and younger inversion events are related to underthrusting of the Dangerous Grounds driven by both the opening of the South China Sea and by NW-directed subduction beneath SE Sabah in the Semporna-Dent Peninsula. In this context the structural complexity of the Baram-Balabac foreland basin reflects the adjustment of deep crustal blocks to far-field tectonic stress.

Tectonomagnetic study in the seismoactive area of Narmada-Son lineament, central India: Preliminary results on repeat field observations

Repeated measurements of the total geomagnetic field on the five profiles have revealed a picture of stress-induced tectonomagnetic effect in the form of secular variation of the total geomagnetic field in the tectonically and seismically active area of Jabalpur and adjoining areas of the Narmada-Son lineament (NSL), central India. For this experiment, a reference base station was established within the study area at Jabalpur. Using proton precession magnetometers with a sensitivity of 0.1 nT, simultaneous measurements of total geomagnetic field were made annually at the base and all field stations. Five cycles of repeated observations have been performed between 2003 and 2007. For data analysis, a difference method has been applied and the residuals have been calculated as secular variations of the total geomagnetic field with values ranging from ±0.1nT to about ±14.6nT/yr over the different stations. The anomalies in secular variation of the total geomagnetic field may be related to anomalous accumulation of tectonic stresses and tensions on the deep fault zones and crustal blocks due to recent geodynamic processes and active geological inhomogeneities in the NSL.

The Maya-Chortís Boundary: A Tectonostratigraphic Approach

This work presents an updated revision of the complex stratigraphic and tectonic relationships that characterize the geologic boundary between the Chortís and Maya continental blocks of the Caribbean region. Based on field, petrologic, structural and geochronological work in key areas of central Guatemala, as well as analysis of the relevant literature, we propose a new tectonostratigraphic structure that more fully appraises the fundamental tectonic role played by major faults that cut across the continental isthmus between the Americas, and bound separate tectonostratigraphic terranes (or fault blocks according to author JDK). Accordingly, we subdivide the area into seven of these units, from south to north: Chortís, Yoro, Sula, El Tambor, Jacalteco, Achí, and Maya, bounded respectively by the Agúan-La Ceiba, Jocotán-Chamelecón, Motagua, Baja Verapaz (defined in this work), and Chixoy-Polochic fault zones. Unfortunately, the extreme paucity of modern geologic data bearing on the pre-Cretaceous cover and basement units in the entire region constitutes a major obstacle for building convincing paleogeographic models to explain the complex tectonic evolution of the area from Precambrian to Cenozoic time. Consequently, this work should be taken as an attempt line to understand more clearly the nature and contact relationships between deep crustal blocks in nuclear Central America, and as a contribution to interpret their geologic evolution in plate tectonic terms.

Tectonic geomorphology of the southeastern Mississippi Embayment in northern Mississippi, USA

We analyzed drainage-basin geometry in part of the southeastern Mississippi Embayment near the New Madrid seismic zone in order to detect areas of lateral stream migration that could indicate recent tectonism. Toward this goal, a field of drainage-basin asymmetry vectors was generated from a digital terrain model and compared to geologic structure, lithofacies, seismicity, remotely sensed lineaments, and major drainage divides. Transverse topographical drainage-basin asymmetry (T-index) results define geomorphic domains in northern Mississippi (33° to 35°N, 88.5° to 90.25°W) that may reflect deep crustal blocks bounded by active faults or flexures. T-index measurements (a proxy for lateral stream migration) of more than 4500 second-order drainage basins produced a two-dimensional field of 282 spatially averaged vectors from which we interpreted 12 domains. Some domain boundaries correspond to mapped faults of two Paleozoic fault systems in our study area, the northeast-striking Mississippi Valley graben system and the northwest-striking Ouachita thrust belt and foreland faults. Several other prominent domain boundaries may be previously unmapped faults (flexures?) parallel to these systems. This interpretation is supported by satellite image analysis of the northeastern study area, which reveals lineaments consistent with our domain boundaries that have strikes that reflect the regional subsurface structural grain.

Tectonic geomorphology of the southeastern Mississippi Embayment in northern Mississippi, USA

Research Article| September 01, 2006 Tectonic geomorphology of the southeastern Mississippi Embayment in northern Mississippi, USA Julio Garrote; Julio Garrote 1Department Geodinamica, Faculty Geología, Universidad Complutense de Madrid, Av. Complutense s/n, 28040 Madrid, Spain Search for other works by this author on: GSW Google Scholar Randel Tom Cox; Randel Tom Cox 2Earth Sciences Department, G-1 Johnson Hall, University of Memphis, Memphis, Tennessee 38152, USA Search for other works by this author on: GSW Google Scholar Charles Swann; Charles Swann 3Mississippi Mineral Resources Institute, 220 Old Chemistry Building, University of Mississippi, University, Mississippi 38677, USA Search for other works by this author on: GSW Google Scholar Michael Ellis Michael Ellis 4Center for Earthquake Research and Information, University of Memphis, Memphis, Tennessee 38152, USA Search for other works by this author on: GSW Google Scholar GSA Bulletin (2006) 118 (9-10): 1160–1170. https://doi.org/10.1130/B25721.1 Article history received: 14 Sep 2004 rev-recd: 03 Apr 2006 accepted: 18 Apr 2006 first online: 08 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Twitter LinkedIn Tools Icon Tools Get Permissions Search Site Citation Julio Garrote, Randel Tom Cox, Charles Swann, Michael Ellis; Tectonic geomorphology of the southeastern Mississippi Embayment in northern Mississippi, USA. GSA Bulletin 2006;; 118 (9-10): 1160–1170. doi: https://doi.org/10.1130/B25721.1 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 We analyzed drainage-basin geometry in part of the southeastern Mississippi Embayment near the New Madrid seismic zone in order to detect areas of lateral stream migration that could indicate recent tectonism. Toward this goal, a field of drainage-basin asymmetry vectors was generated from a digital terrain model and compared to geologic structure, lithofacies, seismicity, remotely sensed lineaments, and major drainage divides.Transverse topographical drainage-basin asymmetry (T-index) results define geomorphic domains in northern Mississippi (33° to 35°N, 88.5° to 90.25°W) that may reflect deep crustal blocks bounded by active faults or flexures. T-index measurements (a proxy for lateral stream migration) of more than 4500 second-order drainage basins produced a two-dimensional field of 282 spatially averaged vectors from which we interpreted 12 domains. Some domain boundaries correspond to mapped faults of two Paleozoic fault systems in our study area, the northeast-striking Mississippi Valley graben system and the northwest-striking Ouachita thrust belt and foreland faults. Several other prominent domain boundaries may be previously unmapped faults (flexures?) parallel to these systems. This interpretation is supported by satellite image analysis of the northeastern study area, which reveals lineaments consistent with our domain boundaries that have strikes that reflect the regional subsurface structural grain. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

LITHOPROBE: a scientific update-new images of the continental crust

LITHOPROBE, Canada's national earth sciences research program which integrates geophysical, geological and geochemical investigations in a collaborative effort among scientists from universities, government and industry to extend and relate surface geology to structures at depth, is up and running. The Lithoprobe Secretariat is established at the University of British Columbia. The Lithoprobe Seismic Processing Facility (LSPF) for research reprocessing of Lithoprobe and related data is installed at the University of Calgary. Access by the Canadian research community will be available through remote site connections. All scientific aspects of the program are in operation and plans for the future are in hand. Some of the spectacular new images of continental crustal structures that have been obtained and their tectonic significance are highlighted in this summary. Individual contributions of specific studies by Lithoprobe scientists are included in this volume.Along the eastern portion of the Southern Cordillera Transect, 270 km of crustal reflection data acquired in 1985 and subsequent magnetotelluric results define the westward extent of autochthonous North American basement (truncated by the crustal scale east-dipping Slocan Lake fault zone), the thickening of Purcell Proterozoic supracrustal rocks by folding and thrusting and a major compressional shear zone underlying the Valhalla gneiss complex. In 1988, Seismic profiling was extended westward across the allochthonous terranes and plutonic complexes to the west coast. About 900 km of 60-fold, 18 s data were recorded by an industry contract crew; initial processing by contract is in progress.In our Appalachian transect, Lithoprobe East, more than 3000 km of marine crustal reflection data have been acquired around Newfoundland and in the Gulf of St. Lawrence. Three deep crustal blocks, each of which exhibits a characteristic Seismic signature, can be traced through the region. Intracrustal reflectors on the Seismic line run across the continental margin northeast of Newfoundland help determine the nature of extensional tectonics and associated sedimentary basin evolution on the rifted margin.The GLIMPCE Transect has enabled a glimpse of the mid-continent crust by recording marine reflection data in the Great Lakes. The sections from Lake Superior reveal — 10 km of sediments overlying a 20 km thick sequence of strongly reflective volcanics and inter-flow sediments, perhaps representing the greatest vertical extent of intra-continental rift deposits on Earth.The original Archean/Early Proterozoic crust is greatly thinned beneath the rift basin. In the Lake Huron/Georgian Bay profile, the Grenville front is imaged as the westernmost reflection of a spectacular 70 km wide band of southeast-dipping reflections that clearly truncates prominent sub-horizontal crustal reflections of the Superior granite-rhyolite terrane.The Kapuskasing Structure Zone is a sequence of lower crustal rocks that have been thrust upward along the Ivanhoe Lake cataclastic zone and are now exposed at the surface. As part of the Kapuskasing Transect, 340 km of regional deep reflection data and 20 km of “ high resolution” data (20 m station spacing, 20 m source interval and a higher sweep range) over the cataclastic zone were recorded in 1987–1988. The Abitibi sub-province of Ontario and Quebec contains mineralized belts for which it is famous. As a preliminary program for the Abitibi-Grenville Transect, 130 km of regional and 65 km of high-resolution Seismic profiles also were recorded in 1987–1988. These were centred over major fault zones with which mineralization is related. Data quality is excellent and the data are in the process of being interpreted.

Crustal structure and surface zonation of the Canadian Appalachians: implications of deep seismic reflection data

In 1986, 1181 km of marine seismic reflection data was collected to 18–20 s of two-way traveltime in the Gulf of St. Lawrence area. The seismic profiles sample all major surface tectono-stratigraphic zones of the Canadian Appalachians. They complement the 1984 deep reflection survey northeast of Newfoundland. Together, the seismic profiles reveal the regional three-dimensional geometry of the orogen.Three lower crustal blocks are distinguished on the seismic data. They are referred to as the Grenville, Central, and Avalon blocks, from west to east. The Grenville block is wedge shaped in section, and its subsurface edge follows the form of the Appalachian structural front. The Grenville block abuts the Central block at mid-crustal to mantle depths. The Avalon block meets the Central block at a steep junction that penetrates the entire crust.Consistent differences in the seismic character of the Moho help identify boundaries of the deep crustal blocks. The Moho signature varies from uniform over extended distances to irregular with abrupt depth changes. In places the Moho is offset by steep reflections that cut the lower crust and upper mantle. In other places, the change in Moho elevation is gradual, with lower crustal reflections following its form. In all three blocks the crust is generally highly reflective, with no distinction between a transparent upper crust and reflective lower crust.In general, Carboniferous and Mesozoic basins crossed by the seismic profiles overlie thinner crust. However, a deep Moho is found at some places beneath the Carboniferous Magdalen Basin.The Grenville block belongs to the Grenville Craton; the Humber Zone is thrust over its dipping southwestern edge. The Dunnage Zone is allochthonous above the opposing Grenville and Central blocks. The Gander Zone may be the surface expression of the Central block or may be allochthonous itself. There is a spatial analogy between the Avalon block and the Avalon Zone. Our profile across the Meguma Zone is too short to seismically distinguish this zone from the Avalon Zone.