scholarly journals The geological framework for Hvideklint, south-east Denmark, using glaciodynamic sequence stratigraphy

2021 ◽  
Vol 47 ◽  
Author(s):  
Stig A. Schack Pedersen ◽  
Peter Gravesen
Keyword(s):  
Sea Level ◽  
Sequence Stratigraphy ◽  
Cross Section ◽  
Cross Sections ◽  
Drill Hole ◽  
Balanced Cross Section ◽  
Geological Cross Section ◽  
Thrust Sheets ◽  
Practical Model ◽  
Complex Architecture

Glaciodynamic sequence stratigraphy provides a practical model for grouping and classifying complex geological data to aid interpretation of past climatic and environmental development in Quaternary successions. The principles of glaciodynamic sequence stratigraphy are applied here to summarise the complex glacial geological framework of Hvideklint on the island of Møn, south-east Denmark. The framework of the superimposed deformed Hvideklint is presented in a reconstructed geological cross-section of Hvideklint. For the construction of the architecture of the glaciotectonic complex, the interpretation of structures below sea level was based on a detailed new survey of the cliff section combined with construction of successive approximation balanced cross-sections. The new description is supported by drill hole data from the Jupiter database. Where chalk is not glaciotectonically deformed, the constructed depth to the top-chalk-surface is generally located about 30 m below sea level. In Hvideklint, thrust sheets with chalk are exposed 20 m above sea level, and the balanced cross-section constructions indicate that the décollement surface for a Hvideklint glaciotectonic complex is located about 80 m below sea level. Between the décollement level and the top of the complex, two or more thrust-fault flat-levels and connecting ramps add to the complex architecture of Hvideklint.

scholarly journals Examining the tectono-stratigraphic architecture, structural geometry, and kinematic evolution of the Himalayan fold-thrust belt, Kumaun, northwest India

Lithosphere ◽  
2019 ◽  
Vol 11 (4) ◽  
pp. 414-435 ◽  
Author(s):  
Subhadip Mandal ◽  
Delores M. Robinson ◽  
Matthew J. Kohn ◽  
Subodha Khanal ◽  
Oindrila Das
Keyword(s):  
Cross Section ◽  
Structural Model ◽  
Kinematic Model ◽  
Thrust Belt ◽  
Main Central Thrust ◽  
Thrust Sheet ◽  
Balanced Cross Section ◽  
Kinematic Evolution ◽  
Thrust Sheets ◽  
Northwest India

Abstract Existing structural models of the Himalayan fold-thrust belt in Kumaun, northwest India, are based on a tectono-stratigraphy that assigns different stratigraphy to the Ramgarh, Berinag, Askot, and Munsiari thrusts and treats the thrusts as separate structures. We reassess the tectono-stratigraphy of Kumaun, based on new and existing U-Pb zircon ages and whole-rock Nd isotopic values, and present a new structural model and deformation history through kinematic analysis using a balanced cross section. This study reveals that the rocks that currently crop out as the Ramgarh, Berinag, Askot, and Munsiari thrust sheets were part of the same, once laterally continuous stratigraphic unit, consisting of Lesser Himalayan Paleoproterozoic granitoids (ca. 1850 Ma) and metasedimentary rocks. These Paleoproterozoic rocks were shortened and duplexed into the Ramgarh-Munsiari thrust sheet and other Paleoproterozoic thrust sheets during Himalayan orogenesis. Our structural model contains a hinterland-dipping duplex that accommodates ∼541–575 km or 79%–80% of minimum shortening between the Main Frontal thrust and South Tibetan Detachment system. By adding in minimum shortening from the Tethyan Himalaya, we estimate a total minimum shortening of ∼674–751 km in the Himalayan fold-thrust belt. The Ramgarh-Munsiari thrust sheet and the Lesser Himalayan duplex are breached by erosion, separating the Paleoproterozoic Lesser Himalayan rocks of the Ramgarh-Munsiari thrust into the isolated, synclinal Almora, Askot, and Chiplakot klippen, where folding of the Ramgarh-Munsiari thrust sheet by the Lesser Himalayan duplex controls preservation of these klippen. The Ramgarh-Munsiari thrust carries the Paleoproterozoic Lesser Himalayan rocks ∼120 km southward from the footwall of the Main Central thrust and exposed them in the hanging wall of the Main Boundary thrust. Our kinematic model demonstrates that propagation of the thrust belt occurred from north to south with minor out-of-sequence thrusting and is consistent with a critical taper model for growth of the Himalayan thrust belt, following emplacement of midcrustal Greater Himalayan rocks. Our revised stratigraphy-based balanced cross section contains ∼120–200 km greater shortening than previously estimated through the Greater, Lesser, and Subhimalayan rocks.

Structure, strain and AMS of the Uzunakhmat thrust sheet (Talas Range, Kyrgyz North Tian Shan)

2020 ◽  
Author(s):  
Anastasia Kushnareva ◽  
Artem Moskalenko ◽  
Alexander Pasenko
Keyword(s):  
Cross Section ◽  
Cross Sections ◽  
Structural Evolution ◽  
Middle Part ◽  
Tien Shan ◽  
Initial Shape ◽  
Thrust Sheet ◽  
Structural Style ◽  
Thrust Sheets ◽  
Tian Shan

<p>The Talas Range forms the northwest part of the Caledonides of the Northern Tian Shan. Based on differences in the structural style, metamorphism and sedimentary successions, three thrust sheets have been identified – the Uzunakhmat, Talas, and Kumyshtag thrust sheets. The Talas and Kumyshtag thrust sheets consist of Neoproterozoic-Ordovician terrigenous and carbonate rock units, whereas the Uzunakhmat thrust sheet consists of Neoproterozoic terrigenous rocks metamorphosed up to greenschist facies. The Uzunakhmat thrust sheet is separated from the Talas and Kumyshtag thrust sheets by the southwest-dipping Central Talas thrust (CTT). The dextral strike-slip Talas-Fergana Fault bounds the Uzunakhmat thrust sheet in the southwest. The main deformation events occurred in the Middle-Late Ordovician.</p><p>Structural and strain studies were done along profiles normal to the strike of folds and faults and located in the northwest and southeast parts of the Uzunakhmat thrust sheet. We also incorporate in our study structural profile in the central part of the Uzunakhmat thrust sheet, documented by Khudoley (1993) and Voytenko & Khudoley (2012).</p><p>The main strain indicators were detrital quartz grains in sandstones. Rf/φ and Normalized Fry methods were used to identify the amount of strain. Oblate ellipsoids predominate with Rxz values varying mostly from 1,6 to 2,4. Long axes of strain ellipsoids are sub-horizontal with the southeast to east-southeast trend. Similar trends have long axes of the anisotropy magnetic susceptibility ellipsoid being parallel to fold axes, cleavage-bedding intersection and mineral lineation as well as the trend of the major thrusts, including CTT.</p><p>The modern shape of the Uzunakhmat thrust sheet is similar to an elongated triangle, pinching out northwest and expanding southeast. Cross-section balancing corrected for the amount of strain shows along-strike decreasing of shortening in the southeast direction. Total shortening varies from 35% to 55% between sections located about 15 km from each other. Such significant variation in shortening corresponds to variation in structural style with much more tight folds and more numerous thrusts for cross-sections with a higher amount of shortening. However, the restored length of all cross-sections is quite similar pointing to the approximately rectangular initial shape of the Uzunakhmat thrust sheet. Our interpretation is that during the Caledonian tectonic events, the Uzunakhmat thrust sheet was displaced in the northwest direction with accompanied thrusting and folding of rock units within the thrust sheet. These deformations formed the modern shape of the thrust sheet in accordance with the amount of shortening detected by cross-section balancing. This interpretation also implies that modern erosion did not significantly affect shape of the Uzunakhmat thrust sheet formed after the Caledonian deformation.</p><p>Khudoley, A.K., 1993. Structural and strain analyses of the middle part of the Talassian Alatau ridge (Middle Asia, Kirgiystan). J. Struct. Geol. 6, 693–706.</p><p>Voytenko N.V., Khudoley A.K. Structural evolution of metamorphic rocks in the Talas Alatau, Tien Shan, Central Asia: Implication for early stages of the Talas-Ferghana Fault. // C. R. Geoscience. 2012. V. 344. P. 138–148.</p>

Restoration of the Caledonian Baltoscandian margin from balanced cross-sections: the problem of excess continental crust

1987 ◽  
Vol 78 (3) ◽  
pp. 197-217 ◽  
Author(s):  
R. A. Gayer ◽  
A. H. N. Rice ◽  
D. Roberts ◽  
C. Townsend ◽  
A. Welbon
Keyword(s):  
Continental Crust ◽  
Cross Section ◽  
Continental Margin ◽  
Cross Sections ◽  
Branch Line ◽  
Norwegian Coast ◽  
Thrust Sheets ◽  
Thrust System ◽  
Basement Ridge ◽  
The Baltic

ABSTRACTConsideration of six balanced cross-sections through parts of the Finnmark Caledonides, N Norway indicates that shortening varies between 25% and 75%. A restored long cross-section across the width of the orogen, constructed with the aid of a branch line map, demonstrates a foreland propagating thrust system, with earlier formed more internal metamorphic nappes thrust SE 330 km under ductile conditions and then carried piggyback ESE a further 296 km on later brittle thrust sheets. Total shortening is 78·7% with a translation of the most internal thrust sheet of 626 km.The restored section suggests that: (1) the rate of propagation of deformation from hinterland to foreland is c. 2·27 cm y−1; (2) incorporation of basement into the nappes resulted from inversion of extensional faults formed during Iapetus rifting; (3) during rifting a Finnmark basement ridge separated a 220 km wide southeasterly Gaissa basin from the passive Iapetus continental margin which was at least 423 km wide; (4) the Finnmark Caledonides resulted from a continent-microcontinent collision which obducted continental crust at least 600 km across the Baltic margin; and (5) the Caledonian Baltoscandian margin prior to Iapetus suturing extended at least 400 km W of the Norwegian coast. On a Bullard reconstruction this overlaps with Laurentian rocks in Greenland. The excess continental crust is accounted for by shortening of the Baltoscandian margin during collision.

scholarly journals A Balanced Geological Cross-Section along Kohalpur – Surkhet Area of Sub-Himalayan Range, Mid-Western Nepal

2019 ◽  
Vol 6 ◽  
pp. 1-8 ◽  
Author(s):  
Nirmal Kafle ◽  
Lelin Raj Dhungel ◽  
Kamala Kanta Acharya ◽  
Megh Raj Dhital
Keyword(s):  
Cross Section ◽  
Accretionary Prism ◽  
Structural Geometry ◽  
Gangetic Plain ◽  
Balanced Cross Section ◽  
Main Boundary Thrust ◽  
Geological Cross Section ◽  
Himalayan Belt ◽  
Indo Gangetic Plain ◽  
Sketch Map

The Sub-Himalayans Zone comprises a tectonic wedge of syn-orogenic sediments along the outer Himalayan Belt. Sediments are integrated into the accretionary prism from the foreland Indo-Gangetic plain, undergo a tectonic cycle within it, and eventually are eroded. The structural sketch map unveils westward-plunging arcuate structures on the leading location of the Outer Belt. A balanced cross-section has been constructed across the Sub-Himalayan Hills of the Kohalpur-Surkhet region of mid-western Nepal in order to determine the structural geometry of the region and to calculate tectonic shortening. The mid-western Nepal Sub-Himalaya has an emergent splay fan geometry with no major prevailing thrust contains the Main Boundary Thrust (MBT), the Bheri Thrust, the Babai Thrust and the Main frontal Thrust (MFT) which are all imbricate of the main decollment which ramp up-section through the 5 km thick tectonic sedimentary prism. North-south shortening across the mid-western Nepal, Kohalpur-Surkhet section has been approximately 29 km, or 55% shortening.

Is the cosmic-ray hadron shower a fractal?

1990 ◽  
Vol 68 (9) ◽  
pp. 906-911 ◽  
Author(s):  
Teruaki Ohnishi
Keyword(s):  
Fractal Dimension ◽  
Sea Level ◽  
Cross Section ◽  
Cross Sections ◽  
Cosmic Ray ◽  
Interaction Cross Section ◽  
Stationary Condition ◽  
Fractal Nature ◽  
Hadron Shower ◽  
Total Interaction

The possible fractal nature of trajectories drawn by cosmic-ray particles in the atmosphere is investigated. In the course of the propagation of a primary cosmic-ray particle from the top of the atmosphere to sea level, it develops a ramified hadron shower, which is constituted mainly of pions and kaons. These hadrons are multiply produced at every collision of the hadron with an air nucleus. If the cross section corresponding to a definite multiplicity of hadrons decreases with the increase of energy E, in such a manner as to be reciprocally proportional to some powers of E, the resultant pattern of the shower possibly becomes fractal. Since the total interaction cross section is considered to be a superposition of many fundamental cross sections each of which corresponds to a definite multiplicity, the actual hadron shower can be interpreted as a superposition of many fractals each of which has an unique fractal dimension. The total energy of the shower has appeared to obey Laplace's equation under a quasi-stationary condition. Some ramified patterns of the cosmic-ray hadron shower are derived with computers.

scholarly journals Expert modelling of a geological cross-section from boreholes: sources of uncertainty and their quantification

2014 ◽  
Vol 6 (2) ◽  
pp. 1687-1721
Author(s):  
R. M. Lark ◽  
S. Thorpe ◽  
H. Kessler ◽  
S. J. Mathers
Keyword(s):  
Statistical Model ◽  
Cross Section ◽  
Cross Sections ◽  
Planning Process ◽  
Route Planning ◽  
Systematic Bias ◽  
Sources Of Uncertainty ◽  
Geological Cross Section ◽  
London Clay ◽  
The Individual

Abstract. We conducted a designed experiment to quantify sources of uncertainty in the expert interpretation of a geological cross-section. A group of 28 geologists participated in the experiment. Each interpreted borehole records which included three Palaeogene bedrock units, including the target unit for the experiment: the London Clay. The set of boreholes was divided into batches from which validation boreholes had been withheld; as a result we obtained 129 point comparisons between the interpreted elevation of the base of the London Clay and its observed elevation in a borehole not used for that particular interpretation. Analysis of the results showed good general agreement between the observed and interpreted elevations, with no evidence of systematic bias. Between-site variation of the interpretation error was spatially correlated, and the variance appeared to be stationary. The between-geologist component of variance was smaller overall, and depended on distance to the nearest borehole. There was also evidence that the between-geologist variance depends on the degree of experience of the individual. We used the statistical model of interpretation error to compute confidence intervals for any one interpretation of the base of the London Clay on the cross-section, and to provide uncertainty measures for decision support in a hypothetical route-planning process. The statistical model could also be used to quantify error-propagation in a full 3-D geological model produced from interpreted cross sections.

scholarly journals Interpretative modelling of a geological cross section from boreholes: sources of uncertainty and their quantification

Solid Earth ◽  
2014 ◽  
Vol 5 (2) ◽  
pp. 1189-1203 ◽  
Author(s):  
R. M. Lark ◽  
S. Thorpe ◽  
H. Kessler ◽  
S. J. Mathers
Keyword(s):  
Statistical Model ◽  
Cross Section ◽  
Cross Sections ◽  
Planning Process ◽  
Route Planning ◽  
Systematic Bias ◽  
Sources Of Uncertainty ◽  
Geological Cross Section ◽  
London Clay ◽  
The Individual

Abstract. We conducted a designed experiment to quantify sources of uncertainty in geologists' interpretations of a geological cross section. A group of 28 geologists participated in the experiment. Each interpreted borehole record included up to three Palaeogene bedrock units, including the target unit for the experiment: the London Clay. The set of boreholes was divided into batches from which validation boreholes had been withheld; as a result, we obtained 129 point comparisons between the interpreted elevation of the base of the London Clay and its observed elevation in a borehole not used for that particular interpretation. Analysis of the results showed good general agreement between the observed and interpreted elevations, with no evidence of systematic bias. Between-site variation of the interpretation error was spatially correlated, and the variance appeared to be stationary. The between-geologist component of variance was smaller overall, and depended on the distance to the nearest borehole. There was also evidence that the between-geologist variance depends on the degree of experience of the individual. We used the statistical model of interpretation error to compute confidence intervals for any one interpretation of the base of the London Clay on the cross section, and to provide uncertainty measures for decision support in a hypothetical route-planning process. The statistical model could also be used to quantify error propagation in a full 3-D geological model produced from interpreted cross sections.

scholarly journals Crustal-scale cross-sections across the NW Zagros belt: implications for the Arabian margin reconstruction

2011 ◽  
Vol 148 (5-6) ◽  
pp. 739-761 ◽  
Author(s):  
J. VERGÉS ◽  
E. SAURA ◽  
E. CASCIELLO ◽  
M. FERNÀNDEZ ◽  
A. VILLASEÑOR ◽  
...  
Keyword(s):  
Cross Section ◽  
Cross Sections ◽  
Receiver Function ◽  
Foreland Basin ◽  
Sedimentary Facies ◽  
Zagros Mountains ◽  
Sarvak Formation ◽  
Seismic Receiver ◽  
Balanced Cross Section ◽  
Shortening Rate

AbstractQuantified balanced and restored crustal cross-sections across the NW Zagros Mountains are presented in this work integrating geological and geophysical local and global datasets. The balanced crustal cross-section reproduces the surficial folding and thrusting of the thick cover succession, including the near top of the Sarvak Formation (~90 Ma) that forms the top of the restored crustal cross-section. The base of the Arabian crust in the balanced cross-section is constrained by recently published seismic receiver function results showing a deepening of the Moho from 42 ± 2 km in the undeformed foreland basin to 56 ± 2 km beneath the High Zagros. The internal parts of the deformed crustal cross-section are constrained by new seismic tomographic sections imaging a ~50° NE-dipping sharp contact between the Arabian and Iranian crusts. These surfaces bound an area of 10800 km2 that should be kept constant during the Zagros orogeny. The Arabian crustal cross-section is restored using six different tectonosedimentary domains according to their sedimentary facies and palaeobathymetries, and assuming Airy isostasy and area conservation. While the two southwestern domains were directly determined from well-constrained surface data, the reconstruction of the distal domains to the NE was made using the recent margin model of Wrobel-Daveau et al. (2010) and fitting the total area calculated in the balanced cross-section. The Arabian continental–oceanic boundary, at the time corresponding to the near top of the Sarvak Formation, is located 169 km to the NE of the trace of the Main Recent Fault. Shortening is estimated at ~180 km for the cover rocks and ~149 km for the Arabian basement, including all compressional events from Late Cretaceous to Recent time, with an average shortening rate of ~2 mm yr−1 for the last 90 Ma.

Electron Irradiation Effects in Polyoxymethylene Crystals Grown Inside Trioxane Crystals

1971 ◽  
Vol 29 ◽  
pp. 78-79
Author(s):  
J. P. Colson ◽  
D. H. Reneker
Keyword(s):  
Cross Section ◽  
Cross Sections ◽  
Detailed Examination ◽  
The Other ◽  
Electron Micrograph ◽  
Irradiation Effects ◽  
Threefold Axis ◽  
Typical Sample ◽  
Polymer Crystals ◽  
Chain Axis

Polyoxymethylene (POM) crystals grow inside trioxane crystals which have been irradiated and heated to a temperature slightly below their melting point. Figure 1 shows a low magnification electron micrograph of a group of such POM crystals. Detailed examination at higher magnification showed that three distinct types of POM crystals grew in a typical sample. The three types of POM crystals were distinguished by the direction that the polymer chain axis in each crystal made with respect to the threefold axis of the trioxane crystal. These polyoxymethylene crystals were described previously.At low magnifications the three types of polymer crystals appeared as slender rods. One type had a hexagonal cross section and the other two types had rectangular cross sections, that is, they were ribbonlike.

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