Rostislav Melichar

9D space – the best way to understand paleostress analysis

Los braquiopodos retzidinos son una fraccion menor de las faunas devonicas de la CordilleraCantabrica (Norte de Espana). Aparte de un par de formas raras, impublicadas, del Praguiense delDominio Palentino y del Emsiense inferior del Astur-Leones, proximas al genero Rhynchospirina, ellinaje alcanzo su maximo de diversidad en la parte superior del Emsiense, con dos especies del generoRetzia, R. adrieni y R. cf. prominula, Cooperispira subferita y, quizas, una forma impublicada dePlectospira. El grupo no es conocido en el resto del Devonico y reaparece en el Pensilvaniense con algunasformas del genero Hustedia. En este trabajo se propone un nuevo taxon de la Familia Retziidae,Argovejia n.gen., de la parte final del Emsiense superior de Asturias y Leon, constituido por su especietipo,A. talenti n.sp. y, quizas, por las formas del Emsiense superior del Macizo Armoricano (Francia)Retzia haidingeri var. armoricana y Retzia haidingeri var. dichotoma.The Ronda Depression is filled by Neogene sediments on the boundary between Subbeticreliefs, with NE-SW structural trends, and the frontal Subbetic Chaotic Complexes. The folding stylein the Subbetic Units of Western Betics is strongly controlled by the rheology of the rocks: thick andmassive beds of Jurassic limestones over Triassic marls and gypsum with plastic behaviour. Main deformationstructures in the sedimentary infill of the Ronda depression are simultaneous box folds withNNE-SSW and WNW-ESE trends that only affect its southwestern part. This distribution of folds isa consequence of the inherited fold trend that affected the basement during Early Burdigalian age.

Polyphase deformation of the Variscan accretionary wedge: an example from the southern part of the Moravian Karst (Bohemian Massif, Czech Republic)

Abstract The presence of two different coeval pre-flysch carbonate facies juxtaposed in numerous profiles in the southern part of the Moravian Karst proves that the Variscan nappe tectonics affected the pre-flysch basement of the main Culmian flysch nappes. Two main thrust events were recognized: (1) a ‘thin-skinned’ event, during which two sedimentary facies were juxtaposed along bedding sub-parallel thrusts, and (2) a ‘thick-skinned’ event, which generated younger thrusts oblique to bedding, involved crystalline rocks of the Brno Massif, and resulted in refolding of the older thrusts.

Palaeostress analysis of a giant Holocene rockslide near Boaco and Santa Lucia (Nicaragua, Central America)

Abstract A giant rockslide occurred on the southern side of an Upper Tertiary shield volcano in central Nicaragua in the Holocene. The failure caused tectonic-like deformation of rock masses and changed the local stress regime. The lower, compressional part of the rockslide produced a stress field with the axis of maximum stress (σ1) parallel to the displacement vector of the main body. The upper part of the rockslide was gravity-driven with σ1 vertical and σ3 horizontal, and oriented SE–NW. The mass tended to move SE. In the crown, the stress field had a subvertical σ1 steeply dipping towards the west. Data at the base of the Santa Lucia Depression, where east- and west-dipping reverse and thrust faults developed, showed that the compressional stress, σ1, was nearly horizontal and east–west oriented, the horizontal σ2 was north–south oriented, and the σ3 was subvertical. These compressional conditions resulted from the collapse of the crown after the main slope failure phase. Simultaneously, along with the gravity relaxation of the main displaced mass, the slopes and mountain slopes along the main scarp depression underwent deep-seated sliding, sagging and flowing.

OATools: An ArcMap add-in for the orientation analysis of geological structures

This paper describes Orientation Analysis Tools (OATools), a new add-in, which has been developed for ArcGIS software (ESRI) to allow the spatial analysis of structural data. These tools bring a complex approach to structural data analysis that highlights the spatial aspect of oriented data. In this paper we introduce the functionality of this add-in, which allows users to plot selected data in azimuthal projection, calculate and plot fold axes, construct density distribution diagrams and rose histograms, and create maps of spatial averages and fold axes. There is a link between projections and maps; therefore, it is possible to select point data in the projection and see their location on the map, and vice versa. Practical use of these tools is demonstrated in a case study of the Svratka and Policka crystalline units (Eastern margin of the Bohemian Massif, Czech Republic), where a large dataset was collected. Using OATools the structural conditions were explored. Major changes in foliation dip directions were detected and the axial surfaces of the folds were determined. We also demonstrate the benefit of applying these tools, together with the potential of GIS with respect to spatial data queries, storage, and visualization.

Tectonic paleostress fields in the southwestern part of Jordan: New insights from the fault slip data in the southeastern flank of the Dead Sea Fault Zone

A new approach for paleostress analysis, using the nine-dimensional space fault slip inversion method, was performed in the southeastern flank of the Jordan-Dead Sea Fault. Five major tectonic episodes with different kinematics were successfully detected from the inversion of a new fault slip data, which thereby caused reactivation of inherited crustal structures and established new ones. These episodes prevailed since Late Cretaceous times, and their chronological constraints were established essentially from the stratigraphic ages of the affected rocks and the crosscutting relationships of successive striae locally observed on the fault planes. During the Late Cretaceous to late Eocene, the area was under a compressional/strike-slip stress regime with a ~E-W trending sigma1. At Oligocene, a strike-slip stress regime with NW-SE striking sigma1 occurred. Both compression regimes correspond to the so-called Syrian Arc Deformation that gave rise to distinctive folds in Jordan and its surrounding areas. An extension with ~N-S to NE-SW trending sigma3 followed the late Oligocene compression event and took place during Miocene time, most probably linked to the opening of the Red Sea-Suez Rift. Late Cenozoic tectonics show the occurrence of two successive compressions, NW-SE then both NE-SW and ~N-S, which generally reflect a continental collisional setting between the Arabian and Eurasian plates.

Numerical paleostress analysis - the limits of automation

The Subandean Basins of South America extending from Trinidad to Tierra del Fuego have been the object of intensive exploratory activities (Fig. 1). The largest amount of hydrocarbons discovered during the last 30 years in these basins was found in complex structural terrains. A total of 59 Billion Barrels of Oil Equivalent (BBOE) have been discovered in areas affected by compressional tectonics. Of these basins, the largest discoveries are in the Furrial Trend of Venezuela (24 BBOE), followed by the Chaco area in Bolivia and Argentina (13 BBOE), the Llanos Foothills of Colombia (4.4 BBOE), and the Madre de Dios Basin of Peru (4.2 BBOE).

The stratigraphy separation diagram-an amazing tool for fault analysis

The Subandean Basins of South America extending from Trinidad to Tierra del Fuego have been the object of intensive exploratory activities (Fig. 1). The largest amount of hydrocarbons discovered during the last 30 years in these basins was found in complex structural terrains. A total of 59 Billion Barrels of Oil Equivalent (BBOE) have been discovered in areas affected by compressional tectonics. Of these basins, the largest discoveries are in the Furrial Trend of Venezuela (24 BBOE), followed by the Chaco area in Bolivia and Argentina (13 BBOE), the Llanos Foothills of Colombia (4.4 BBOE), and the Madre de Dios Basin of Peru (4.2 BBOE).

Large landslide stress states calculated during extreme climatic and tectonic events on El Hierro, Canary Islands

Composed volcanic edifices are particularly prone to large-scale failures—these often result from the acceleration of preexisting deep-seated gravitational slope deformations. Consequently, a complete understanding of the kinematic behaviour of such slope deformations would represent an important step towards mitigating against human casualties or fatalities and damage to critical infrastructure. In this manuscript, a 9-month time series of three-dimensional fault displacement measurements has been used to determine the stress states of the San Andrés Landslide on El Hierro in the Canary Islands. These stress states have been calculated on the basis of single-displacement events using a novel approach which only requires information about the magnitude of the movement vector and its orientation. The analysis focused on four specific periods: a reference period in November 2013; an extreme rainfall event at the beginning of December 2013; and two endogenous impulses at the end of December 2013 and during the middle of March 2014. On the basis that the direction of principal stress represents a marker for the direction of landslide mass movement, it has been possible to define six landslide activity modes which correspond to specific stress states. The response of the landslide to the extreme rainfall event was immediate and reflected increasing saturation of the porous landslide mass. The response of the landslide to the endogenous impulses was more complicated as compressional pulses often alternated with gravitational relaxation. In this study, it is demonstrated that the landslide stress state can be determined on the basis of a single-displacement event whenever fault displacements are monitored in three dimensions. This innovative approach may represent a valuable step towards a complete understanding of the kinematic behaviour of potentially catastrophic slope deformations, particularly those which are in a critical stability state.

Thrust tectonics of the Upper Jurassic limestones in the Pavlov Hills (Outer Western Carpathians, Czech Republic)

Abstract The Pavlov Hills are formed by separated limestone blocks previously identified as klippen. A new flat-ramp-flat thrust model of the Pavlov Hills is formulated in this paper. The main tectonic detachment is located at the base of the limestone plate and other subsidiary detachments are located within the nodular limestone horizon and also at the base and top of the Upper Cretaceous deposits. The ramps are situated in the Klentnice Fm and Ernstbrunn Lst. The ramp angle was determined by structural evidence combined with interpretation of seismic profiles. Two parallel antiformal structures plunging to the NE are recognized within the study area. The antiformal fold axes are gently plunging to the NE so the anticlines are not ideal for 3-point hydrocarbon trap setting. These anticlines were subsequently cut by sinistral strike-slip faults perpendicular to the fold axis which resulted in the formation of a large-scale pseudo en-echelon structure in an approximate north–south direction.

Peek inside the black box of calcite twinning paleostress analysis

Los braquiopodos retzidinos son una fraccion menor de las faunas devonicas de la CordilleraCantabrica (Norte de Espana). Aparte de un par de formas raras, impublicadas, del Praguiense delDominio Palentino y del Emsiense inferior del Astur-Leones, proximas al genero Rhynchospirina, ellinaje alcanzo su maximo de diversidad en la parte superior del Emsiense, con dos especies del generoRetzia, R. adrieni y R. cf. prominula, Cooperispira subferita y, quizas, una forma impublicada dePlectospira. El grupo no es conocido en el resto del Devonico y reaparece en el Pensilvaniense con algunasformas del genero Hustedia. En este trabajo se propone un nuevo taxon de la Familia Retziidae,Argovejia n.gen., de la parte final del Emsiense superior de Asturias y Leon, constituido por su especietipo,A. talenti n.sp. y, quizas, por las formas del Emsiense superior del Macizo Armoricano (Francia)Retzia haidingeri var. armoricana y Retzia haidingeri var. dichotoma.The Ronda Depression is filled by Neogene sediments on the boundary between Subbeticreliefs, with NE-SW structural trends, and the frontal Subbetic Chaotic Complexes. The folding stylein the Subbetic Units of Western Betics is strongly controlled by the rheology of the rocks: thick andmassive beds of Jurassic limestones over Triassic marls and gypsum with plastic behaviour. Main deformationstructures in the sedimentary infill of the Ronda depression are simultaneous box folds withNNE-SSW and WNW-ESE trends that only affect its southwestern part. This distribution of folds isa consequence of the inherited fold trend that affected the basement during Early Burdigalian age.