Pre-folding fracturing in a foredeep environment: insights from the Carseolani Mountains (central Apennines, Italy)

2021 ◽  
pp. 1-17
Author(s):  
Marco Mercuri ◽  
Luca Smeraglia ◽  
Manuel Curzi ◽  
Stefano Tavani ◽  
Roberta Maffucci ◽  
...  
Keyword(s):  
Structural Analysis ◽  
Fracture Pattern ◽  
Pressure Solution ◽  
Fold Axis ◽  
Field Observations ◽  
Central Apennines ◽  
Structural Position ◽  
Deformation Structures ◽  
Thrust Belts ◽  
Belt System

Abstract Bedding-perpendicular joints striking parallel (longitudinal) and perpendicular (transverse) to both the axis of the hosting anticline and the trend of the foredeep-belt system are widely recognized in fold-and-thrust belts. Their occurrence has been commonly attributed to folding-related processes, such as syn-folding outer-arc extension, although they can also be consistent with a pre-folding foredeep-related fracturing stage. Here we report the pre-folding fracture pattern affecting the Pietrasecca Anticline, in the central Apennines (Italy), resolved by a detailed field structural analysis. Field observations, scan-lines and interpretation of virtual outcrops were used to study the intensity, distribution and the orientations of fracture pattern along the anticline. The fracture pattern of the Pietrasecca Anticline consists of longitudinal and transverse joints, oriented approximately perpendicular to bedding, and of a pre-folding longitudinal pressure-solution cleavage set, which is oblique to bedding regardless of the bedding dip. Cross-cutting relationships show that joints predated the development of the pressure-solution cleavage. Furthermore, joint intensity does not relate to the structural position along the anticline. Taken together, these observations suggest that jointing occurred in a foredeep environment before the Pietrasecca Anticline growth. Our work further demonstrates that joints striking parallel and orthogonal to the main fold axis do not necessarily represent syn-folding deformation structures.

Pre- to syn-folding closed paleofluid system conditions and their opening in late- to post-folding structural evolution: the case of Urgonian platform carbonates folded in the Parmelan anticline, Bornes Massif, external Western Alps

2021 ◽  
Author(s):  
Luigi Berio ◽  
Silvia Mittempergher ◽  
Fabrizio Storti ◽  
Fabrizio Balsamo ◽  
Stefano M. Bernasconi ◽  
...  
Keyword(s):  
Open System ◽  
Closed System ◽  
Fluid Migration ◽  
Fold Axis ◽  
Isotopic Data ◽  
Element Geochemistry ◽  
Secondary Porosity ◽  
Rock Interaction ◽  
Thrust Belts ◽  
The Impact

<p>Fluid systems in fold-thrust belts typically evolve from hydrologically closed to open, as a consequence of the incremental development of brittle deformation. The spatial distribution of fold-related fractures depends, among other factors, on the kinematics of folding and on the presence of inherited pre-folding structures. An improved understanding of the impact of the incremental evolution of deformation patterns on fluid migration and accumulation is crucial for industrial purposes. Here, we discuss the evolution of the fluid-rock system of the Parmelan anticline, in the Dauphinois units of the northern Subalpine Chains (Bornes Massif). We combined a detailed structural analysis in the Lower Cretaceous units (e.g. Urgonian Limestones) with the study of syn-tectonic calcite cements, by coupling stable and clumped isotope analysis with trace and major element geochemistry, radiogenic Sr isotopic data, and fluid inclusion microthermometry. The older calcite cements associated with the pre-folding structural assemblages precipitated from an <sup>18</sup>O-enriched fluid at temperatures between 90 and 115 °C. This first fluid type was thermally equilibrated with the host rock under maximum burial conditions in the Alpine Foreland and its isotopic composition has been interpreted to reflect a high degree of fluid-rock interaction in a closed system. Trace and major elements and Sr isotopes support a mixed meteoric-marine origin of this fluid, possibly trapped during subaerial platform exposure in the forebulge and then mixed with Eocene seawater. Closed system and rock-buffered conditions persisted during incipient folding whereas, during late folding, longitudinal (i.e. axial parallel) deformation structures allowed fluid circulation in an open system. Open system conditions initially occurred only in crest-limb transitional domains characterized by an higher deformation intensity. By contrast, during post-folding transpression,  the formation of a persistent vein set oblique to fold axis allowed external fluids to migrate in the anticline crest. Younger calcite cements precipitated from moderately warm (55-66 °C) <sup>18</sup>O-depleted meteoric fluids during the late- to post-folding stages. Our compositional and Sr isotopic data exclude any contribution from basement-derived ascending fluids and rule out a possible downward circulation of these meteoric fluids at basement depths. Our results indicate that, in regional anticlines of shallow crustal sectors in foreland fold-thrust belts, a significant amount of secondary porosity can be produced in the pre-folding stages when the hydromechanical stratigraphy likely preserves closed conditions and regional stratigraphic seals can prevent upward fluid migration during the entire tectonic evolution.</p>

Tectonic subdivisions in thrust belts – cleaning up the western Northern Calcareous Alps (NCA)

2020 ◽  
Author(s):  
Hugo Ortner ◽  
Sinah Kilian
Keyword(s):  
Northern Calcareous Alps ◽  
Field Observations ◽  
Southern Germany ◽  
Northern Calcareous ◽  
Thrust Belts ◽  
Formal Framework ◽  
Thrust Sheets ◽  
Comprehensive Mapping

<p>Tectonic subdivisions of larger geologic units reflect the geologic knowledge at the time of creation. In many thrust belts the original subdivisions had been created during the first comprehensive mapping campaigns at the end of the 19<sup>th</sup> to early 20<sup>th</sup> century and reflect the geologic knowledge at that time. Even if many thrusts were identified correctly, no formal framework existed to give guidelines of how to distinguish tectonic units. Nevertheless, these subdivisions are still in use.</p><p>We analyze the thrust sheets of the Northern Calcareous Alps of western Austria and southern Germany and test the implicit assumptions underlying most tectonic subdivisions against field observations:</p><p>Assumption 1: Thrust transport is large and thrusts do not end laterally. However, several major thrusts do loose stratgraphic offset and end laterally.</p><p>Assumption 2: Allochthons are surrounded by thrusts on all sides. Unfortunately, any fault has been used to delimit allochthons.</p><p>Assumption 3: Thrusting should bring old on young rocks. In some cases, allochthons have been delimited by out-of-sequence thrusts, that stack young on old rocks. In other cases, the allochthon is a mountain-size glide block that was buried by younger sediments, and the trace of the thrust is an unconformity in the field.</p><p>As a consequence we propose a revised tectonic subdivision of the western part of the NCA, that avoids some of the problems discussed here, and is entirely based on the emplacement of old-on-young rocks across thrusts.</p>

NATURE AND RESIDENTIAL ENVIRONMENT IN THE FIRST GARDEN CITIES IN GALICIA: “SALWATOR” IN KRAKOW AND “NOVYI SVIT” IN LVIV

2021 ◽  
Vol 7 (2) ◽  
pp. 243-252
Author(s):  
Tyrchyn B ◽  
Keyword(s):  
Structural Analysis ◽  
Residential Environment ◽  
Comprehensive Approach ◽  
Town Planning ◽  
Garden City ◽  
Field Observations ◽  
Scientific Methods ◽  
Garden Cities ◽  
General Scientific ◽  
Historical Comparative

The article discloses the peculiarities of the nature and residential environment in the first garden cities in Galicia: “Salwator” in Krakow and “Novyi Svit” in Lviv. The topicality of the issue is predetermined by the need for supplementing and developing available scientific researches related to the study of the garden city concept as well as for analyzing profoundly and comparing the architectural and townplanning structures of the garden cities in Galicia at the early stages of their development. Both general scientific methods (historical, comparative, structural analysis), and special field observations have been used. This comprehensive approach has enabled us to point out the special features (planning, functional) of the garden cities as exemplified by Lviv and Krakow. It has been proven that the development of the architecture and town planning of the above cities in the early ХХth century corresponds to the general European trends, while the concept of garden cities was implemented in a fragmented way, that is in the form of gardens-on-the-outskirts.

Contrasting transient and steady-state rivers crossing active normal faults: new field observations from the Central Apennines, Italy

2007 ◽  
Vol 19 (4) ◽  
pp. 529-556 ◽  
Author(s):  
Alexander C. Whittaker ◽  
Patience A. Cowie ◽  
Mikaël Attal ◽  
Gregory E. Tucker ◽  
Gerald P. Roberts
Keyword(s):  
Steady State ◽  
Normal Faults ◽  
Field Observations ◽  
Central Apennines ◽  
Transient And Steady State

scholarly journals Structural variation in Old English root clauses

2008 ◽  
Vol 20 (3) ◽  
pp. 367-407 ◽  
Author(s):  
Susan Pintzuk ◽  
Eric Haeberli
Keyword(s):  
Structural Analysis ◽  
Old English ◽  
Structural Variation ◽  
Verb Second ◽  
Structural Position ◽  
Subordinate Clauses ◽  
Traditional Assumption ◽  
Constituent Order ◽  
Basic Constituent ◽  
Finite Verb

AbstractA standard observation concerning basic constituent order in Old English (OE) is that the position of finite verbs varies by clause type. In root clauses, the finite verb tends to occur toward the beginning of the clause, and we frequently find Verb Second (V2) order. In contrast, in subordinate clauses, finite verbs generally occur toward the end of the clause, and these clauses are frequently verb-final. We challenge the traditional assumption that verb-final orders and, hence, the occurrence of the finite verb in a head-final structural position are rare in OE root clauses. We present new data demonstrating that the frequency of head-final structure in OE root clauses is much higher than previously acknowledged. We then explore some of the implications of this finding for the general structural analysis of OE.

scholarly journals Structural analysis of earth construction’s vaults: Case of underground tombs of Chogha Zanbil

2020 ◽  
Vol 19 (3) ◽  
pp. 366-380
Author(s):  
Hamed Niroumand ◽  
◽  
Sara Hosseini ◽  
Arzuhan Burcu Gültekin ◽  
Juan Antonio Barceló ◽  
...  
Keyword(s):  
Structural Analysis ◽  
Field Observations ◽  
Bending Moments ◽  
Pressure Force ◽  
Literature Study ◽  
Shear Forces ◽  
Lime Mortar ◽  
World Heritage List ◽  
Outstanding Universal Value ◽  
The Right

The 3300-year-old Chogha Zanbil is the largest and best-preserved five levelled pyramidal earth ziggurat outside Mesopotamia, which was inscribed on UNESCO’s World Heritage List. Underground tombs of Chogha Zanbil are accepted as outstanding instances in Iran and consist of vaults, which are built with special methods by Elamite architects. In this context, the main purpose of this paper is to contribute to sustain the outstanding universal value of the Chogha Zanbil. For that purpose, this paper puts forward a structural analyse of the vaults of five Chogha Zanbil underground tombs, which were built inside the ground by brick, lime mortar, plaster and bitumen materials. Data for underground tombs and vaults were collected upon field observations and literature study. SAP software was used to determine the way the forces are transmitted through the vaults, the conditions of bending moments, the shear forces. As a result, it has been observed that the bending in the vaults turns into pressure force that is perfectly resisted by bricks. In conclusion, it was ascertained that the vaults of the Chogha Zanbil underground tombs were built with the right techniques at that time, so that the vaults still have solid behaviour after thousands of years and remained completely healthy to this day.

The role of inherited structures and basin geometry during the 3D inversion of a passive continental margin: the case of the Doldenhorn-Aar Massif system (Central Swiss Alps)

2021 ◽  
Author(s):  
Ferdinando Musso Piantelli ◽  
David Mair ◽  
Marco Herwegh ◽  
Alfons Berger ◽  
Eva Kurmann ◽  
...  
Keyword(s):  
Continental Margin ◽  
Large Scale ◽  
Passive Continental Margin ◽  
Swiss Alps ◽  
Cylindrical Shape ◽  
Structural Position ◽  
Structural Style ◽  
Thrust Belts ◽  
Fold And Thrust Belts ◽  
Aar Massif

<p>Inversion of passive margins and their transportation into fold-and-thrust belts is a critical stage of mountain building processes and their structural interpretation is fundamental for understanding collisional orogens. Due to the multitude of parameters that influence their formation (e.g. the interaction between sedimentary cover and basement, the mechanical stratigraphy or the rheology of different rock types) as well as along-strike internal variations, a single cross-sectional view is insufficient in exploring the 3D evolution of a fold-and-thrust belt. Hence, a 3D geological characterization is required to better comprehend such complex systems. Based on a detailed digital map, a 3D structural model of the current tectonic situation and sequential retrodeformation, we elaborate the 3D evolution of a part of the former European passive continental margin. In this setting, we focus on the Doldenhorn Nappe (DN) and the underlying western Aar massif (external Central Alps, Switzerland). The DN is part of the Helvetic nappe system and consists of a large-scale recumbent fold with a thin inverted limb of intensively deformed sediments (Herwegh and Pfiffner 2005). The sedimentary rocks of the DN were deposited in Mesozoic-Cenozoic times in a small-sized basin, which has been inverted during the compression of the Alpine orogeny (Burkhard 1988). Along NNW-SSE striking geological cross-sections, restoration techniques reveal the original asymmetric triangular shape of the DN basin and how the basin has been exhumed from ~ -12 km (Berger et al. 2020) to its present position at 4km elevation above sea level throughout several Alpine deformation stages. Moreover, the model allows to visualize the current structural position of the DN and the massif as well as the geometric and overprinting relationships of the articulated deformation sequence that shaped the investigated area throughout the Alpine evolution. Here we document that: (i) the DN is a strongly non-cylindrical recumbent fold that progressively pinches out toward the NE; (ii) significant along-strike (W-E) stratigraphy thickness variations are reflected in structural variations from a single basal thrust deformation (W) to an in-sequence thrust deformation (E); and (iii) the progressive exhumation of the basement units towards the E and thrusting towards the N. In this context, special emphasis is given to illustrate how three-dimensional geometry of inherited pre-orogenic structures (e.g., Variscan-Permian and rifting related basement cover structures) play a key role in the structural style of fold-and-thrust belts. In summary, today’s structural position of the DN is the result of the inversion of a small basin in an early stage of thrusting, which was followed by sub-vertical buoyancy driven exhumation of the Aar massif and subsequent thrust related shortening. All three stages are deeply coupled with an original non-cylindrical shape of the former European passive continental margin.</p>

Preface: Structural analysis of fold-and-thrust belts

2010 ◽  
Vol 45 (5-6) ◽  
pp. 487-488 ◽  
Author(s):  
Richard Lisle ◽  
Josep Poblet
Keyword(s):  
Structural Analysis ◽  
Thrust Belts ◽  
Fold And Thrust Belts
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