Uplift Of Hanging Wall Research Articles

Paleoseismological Investigations along Joggers Park Fault, Port Blair, South Andaman: Implications towards Delineation of Blind Thrusting and Related Crustal Deformation through Ground Penetrating Radar (GPR) and Electrical Resistivity Techniques (ERT and VES)

ABSTRACT A comprehensive paleoseismological investigations was carried out along Joggers Park Fault (striking NW-SE) reveals pervasive traces of active compressional tectonics (blind thrusting) and shallow-surface recent tectonic signatures along the fault. The geometry and trends in the tectonic deformation of the blind zone (shallow-subsurface stratigraphy) were examined with GPR and electrical resistivity tomography (ERT) and vertical electrical sounding (VES), strongly demonstrates severe tectonic deformation (persistent tectonic style) from Quaternary to Holocene times in a compressive stress regime. The surface manifestation of deformation (topographic expression) along the fault can be marked as hanging wall uplift and can be visually observed in the exposed sections at nearly half kilometer distance from the table land of Joggers Park in the form of a well-defined disconnected high angle thrust fault scarp (reverse fault). The reverse fault kinematically and intimately linked with underlying fault geometry provides adduced evidence to evaluate strike displacement profiles (displacement length relationship) along the fault. In addition, deformed stacked colluvial wedge below the scarp represents a powerful basis to calibrate recent and long term slip rates of the underlying fault.

Coupling sequential restoration of balanced cross sections and low-temperature thermochronometry: The case study of the Western Carpathians

In this paper, a new approach is applied to test a proposed scenario for the tectonic evolution of the Western Carpathian fold-and-thrust belt–foreland system. A N-S balanced section was constructed across the fold-and-thrust belt, from the Polish foreland to the Slovakia hinterland domain. Its sequential restoration allows us to delineate the tectonic evolution and to predict the cooling history along the section. In addition, the response of low-temperature thermochronometers (apatite fission-track and apatite [U-Th]/He) to the changes in the fold-and-thrust belt geometry produced by fault activity and topography evolution are tested. The effective integration of structural and thermochronometric methods provides, for the first time, a high-resolution thermo-kinematic model of the Western Carpathians from the Early Cretaceous onset of shortening to the present day. The interplay between thick- and thin-skinned thrusting exerts a discernible effect on the distribution of cooling ages along the profile. Our analysis unravels cooling of the Outer Carpathians since ca. 22 Ma. The combination of thrust-related hanging-wall uplift and erosion is interpreted as the dominant exhumation mechanism for the outer portion of the orogen. Younger cooling ages (13–4 Ma) obtained for the Inner Carpathian domain are mainly associated with a later, localized uplift, partly controlled by extensional faulting. These results, which help unravel the response of low-temperature thermochronometers to the sequence of tectonic events and topographic changes, allow us to constrain the tectonic scenario that best honors all available data.

Lateral variations in tectonic style across cross-strike discontinuities: an example from the Central Apennines belt (Italy)

In foreland thrust belts, abrupt lateral changes in tectonic style, structural–stratigraphic features, and topography usually occur across cross-strike faults. The Central Apennines of Italy offer an exceptional scenario of lateral variations in tectonic setting. Here, the Sangro Volturno oblique thrust ramp (SVOTR) represents the outer thrust front of the Pliocene–Quaternary foreland thrust system, confining southward the axial culmination of the orogen that occurs in the Central Apennines. We present an interpretation of the Pliocene–Quaternary evolution of this cross-strike fault through an integrated dataset including structural-geological mapping and subsurface onshore seismic reflection profiles. The interpretation of the structural framework is augmented by the analysis of low-temperature thermochronometers from 32 new sites extending across the subsurface transverse structure. As evidenced by seismic line interpretation, the localization and development of the SVOTR have been influenced by inherited extensional faults within a positive inversion tectonics context. The regional distribution of the maximum paleotemperature values across the SVOTR constrains the original extent of the allochthonous thrust sheet over all its hanging-wall and footwall blocks. The Pliocene–Quaternary thrusting and inversion of SVOTR caused the strong hanging-wall uplift, which brought to the complete erosion of the allochthonous units and the exhumation of the Adria units. The integrated analysis of low-temperature thermochronometers and structural evidence as applied in the study case can define the role of major cross-strike discontinuities in foreland thrust belts, by constraining and verifying their tectonics inversion significance and the amount of related exhumation.

Late Pleistocene structural evolution of the Camarillo fold belt: Implications for lateral fault growth and seismic hazard in Southern California

The Camarillo fold belt in the Western Transverse Ranges poses a significant seismic hazard to nearly one million people living in Southern California, yet few published geologic or geochronological data from this fold belt exist. The Camarillo fold belt is composed of several south-verging, west-plunging anticlines that characterize the western extent of the Simi fault zone, which extends for 40 km through urbanized Ventura and Los Angeles Counties. Surface and subsurface geologic data are utilized to accurately construct five cross sections within discrete structural domains to assess the local style of deformation, and to quantify the magnitudes of fault slip, fault- and fold-related uplift, and percent shortening. Eight new optically stimulated luminescence (OSL) dates from three paleoseismic trenches and six numerical dates from a previous study were utilized to quantify the timing and rates of deformation on discrete faults and folds. The onset of deformation in the Camarillo fold belt is everywhere younger than ca. 125 ka and locally as young as ca. 25 ka. Quaternary deformation occurs on reactivated steeply dipping (70°) Miocene faults, with shortening being largely accommodated in a narrow zone (<2 km) of folding where fold-related uplift is typically twice as great as hanging-wall uplift in response to fault slip. A minimum fault slip rate between 0.8 mm/yr and 1.4 mm/yr, a recurrence interval of 715–1100 yr, and a maximum Mw 6.8 earthquake for faults within the Simi fault zone is estimated, which are comparable to other better-studied fold belts in Southern California. A model of punctuated lateral fault propagation is proposed to explain westward growth of the Simi fault, which occurs in discrete pulses that are separated by intervals of fault displacement accumulation and fold amplification during constant-fault-length conditions. Lateral fault growth is limited in space and time by an orthogonal north-striking fault set, which juxtaposes a series of west-plunging anticlines that decrease in structural relief and age toward the west.

Late Cenozoic regional uplift and localised crustal deformation within the northern Arabian Platform in southeast Turkey: Investigation of the Euphrates terrace staircase using multidisciplinary techniques

We present the results of detailed field investigations of the fluvial succession exposed along the Euphrates valley adjoining the Atatürk Dam in the northern part of the Arabian Platform within SE Turkey. This work, which has used Differential GPS surveying to obtain accurate heights of deposits and Shuttle Radar Topographic Mission imagery for location purposes, has included documentation of many fresh sections exposed by quarrying. The work has been supplemented by unspiked KAr dating of late Middle Miocene to Late Miocene basalt flows, which are widespread in the region, providing a chronology for the early stages of development of this river system following regional emergence above sea-level in the early Middle Miocene. For example, beside the Atatürk Dam Lake at Siverek İskelesi, basalt dated to 10.24±0.22Ma (±2σ) caps a polymict Euphrates gravel some 80m above the modern river; this is the oldest Euphrates terrace currently recognised. However, amounts and rates of fluvial incision are shown to vary across the northern Arabian Platform in a complex manner, due to the interaction between regional uplift and localised vertical crustal motions caused by slip on active reverse faults beneath anticlines. The study reach downstream of the Atatürk Dam includes the footwall of one such fault, beneath the Bozova Anticline; we estimate that the resulting rate of localised subsidence, superimposed onto the regional uplift that has also been occurring, has been ~0.01mma−1 during the present phase of crustal deformation, which began at ~3.7–3.6Ma, but was higher, maybe ~0.03mma−1, during the previous phase, which began at ~6 Ma, when the pattern of plate motions in the surrounding region was different. A large palaeo-lake centred north of the present study region around the city of Adıyaman is inferred to have existed during this ~6Ma to ~3.7–3.6Ma phase of plate motion, apparently because the relatively rapid localised hanging-wall uplift on the northern flank of the Bozova Anticline ‘dammed’ the Euphrates valley near the site of the modern Atatürk Dam. The uppermost part of a thick fluvial aggradation west of the Euphrates near Karababa Bridge, inferred to date from around the Mid Pliocene, reaches ~100m above the modern river and, after correction for an estimated ~30m of localised subsidence and by ~50m for subsequent downstream lengthening of the Euphrates channel, indicates ~180m of subsequent regional uplift. The Euphrates then incised to within ~20m of its present level by the mid Early Pleistocene, then a switch to regional subsidence accompanied the deposition of a second thick fluvial aggradation, the top of which is ~70m above the modern river. Subsequent renewed regional uplift, following the Mid-Pleistocene Revolution, has resulted in the development of a succession of fluvial terraces, typically inset into these older aggradations, which are correlated with the cold stages of Milankovitch climate cycles. The early part of the Euphrates chronology, constrained mainly by the disposition of basalt flows, indicates ~800m of regional uplift since the early Middle Miocene, of which an estimated ~330m is masked by the subsequent downstream lengthening of the river. Components of localised uplift and subsidence, caused by slip on reverse faults beneath anticlines, are superimposed onto this regional pattern, the hanging-wall uplift being much larger (in one case, roughly five times larger) than the footwall subsidence. Our results provide, for the first time, detailed documentation of the complex development of the Euphrates valley in SE Turkey during the Late Cenozoic, due to the interaction between regional uplift and localised crustal deformation. This work also demonstrates the benefits of applying multidisciplinary techniques to investigate an important, but hitherto poorly documented, river system.

Tectonostratigraphic evolution of the Morichito piggyback basin, Eastern Venezuelan Basin

The Morichito piggyback basin (MPB) is a SW–NE-oriented depocenter in the Eastern Venezuelan Foreland Basin (EVFB). This piggyback basin formed by overlying the Pirital thrust during the middle to late Miocene as a result of oblique collision between the Caribbean and South-American Plates. The MPB covers an area encompassing approximately 1000 km 2 between the Serrania del Interior range and the Pirital high, which is a hanging wall uplift along the Pirital thrust that acts as a confining barrier on the southern boundary of the MPB. Previous studies have tried to address the tectonostratigraphic significance of the MPB, but new biostratigraphic information and recently acquired 3D seismic data have allowed us to expand the understanding of this basin. The MPB occupies a relatively small area of the EVFB; however, the MPB contains a valuable stratigraphic record that can be used to unveil the timing of the main deformational events that took place in the EVFB. This work presents the tectonostratigraphic evolution of the MPB by defining four tectonostratigraphic sequences (T1–T4). Each sequence was defined on the basis of integration of well logs, biostratigraphy, and seismic geomorphological interpretations. T1 (24–16 Ma) (late Oligocene to middle Miocene), which was deposited in shallow-marine environments, extends to the south of the Pirital high beyond the boundaries of the MPB. T1 is equivalent to the early foredeep stage of the EVFB, having been formed when structural deformation and uplifting were already occurring to the north on the proto-Serrania del Interior range (∼24–16 Ma) and the Pirital thrust was active (∼22 Ma). T2 (16–11 Ma) (middle to late Miocene) is composed of alluvial-fan deposits derived from the proto-Serrania del Interior range. The geometry and internal configuration of T2 indicate that during this time the basin was transitioning from an open-foreland basin to a confined piggyback basin. During deposition of T2, the Pirital fault was active as an out-of-sequence thrusting event (16–∼11 ma). T3 (late Miocene) and T4 (early Pliocene to Recent), composed of shallow-marine and fluvial deposits, were deposited in an already restricted piggyback basin. The Pirital high was already in place during deposition of T3 (∼11–9.3 ma). T3 and T4 represent the final phases of MPB infilling, when tectonic activity and subsidence were at their lowest rates. MPB sedimentary infilling dates the activity of thrusting events in the proto-Serrania del Interior (∼24–16 Ma), timing of maximum deformation associated with the Pirital out-of-sequence thrusting event (16–∼11 Ma), timing of final emplacement of the Pirital high (∼11–9.3 Ma), and the beginning of tectonic quiescence (<5.2 Ma).

Subsidence, Compaction, and Gravity Sliding: Implications for 3D Geometry, Dynamic Rupture, and Seismic Hazard of Active Basin- Bounding Faults in Southern California

In southern California, high rates of measured geodetic shortening occur where active basin-bounding faults thrust early-Cenozoic rocks over young uncon- solidated sediments. This implies that compaction, subsidence, and other nonelastic processes of footwall deformation may play an important role in contributing to the high rates of observed crustal strain. Even in the absence of active tectonic short- ening, sediment compaction alone can produce surficial motions that mimic deep fault slip or elastic strain accumulation. Differential compaction and subsidence of footwall sediments relative to hanging-wall rocks can lead to increased vertical sep- aration, basinward collapse, and fault rotation about horizontal axes. Such effects contribute to net horizontal and vertical motions in both geologic and geodetic data, and—if not properly accounted for—result in incorrect estimates of the inferred seismic hazard. Subsidence and compaction also increase the potential for gravity sliding toward the basin and the development of significant nonplanar 3D fault geometry. A prime example occurs along the San Cayetano fault that bounds the eastern Ventura basin. At shallow levels, a large thrust sheet (the Modelo Lobe) with low dip extends out in front of the more steeply dipping, planar fault segment by over 4 km, is nearly 2 km thick, and occupies over 60 cubic km. This geometry is strongly indicative of gravity-driven failure resulting from hanging-wall uplift, basinward tilt, and collapse, enhanced by footwall subsidence and compaction. Failure of this mega-slide off the hanging-wall block most likely occurred within the Rincon Formation, a thick ductile shale sequence that often accommodates detachment slip. This 3D geometry has significant implications for how the fault may behave during dynamic rupture and implies that additional care should be taken in extrapolating near-surface measure- ments or estimates of fault slip and dip to seismogenic depths.

A remote sensing study of active folding and faulting in southern Kerman province, S.E. Iran

Geomorphological observations reveal a major oblique fold-and-thrust belt in Kerman province, S.E. Iran. The active faults appear to link the Sabzevaran right-lateral strike-slip fault in southeast Iran to other strike-slip faults within the interior of the country and may provide the means of distributing right-lateral shear between the Zagros and Makran mountains over a wider region of central Iran. The Rafsanjan fault is manifest at the Earth's surface as right-lateral strike-slip fault scarps and folding in alluvial sediments. Height changes across the anticlines, and widespread incision of rivers, are likely to result from hanging-wall uplift above thrust faults at depth. Scarps in recent alluvium along the northern margins of the folds suggest that the thrusts reach the surface and are active at the present-day. The observations from Rafsanjan are used to identify similar late Quaternary faulting elsewhere in Kerman province near the towns of Mahan and Rayen. No instrumentally recorded destructive earthquakes have occurred in the study region and only one historical earthquake (Lalehzar, 1923) is recorded. In addition GPS studies show that present-day rates of deformation are low. However, fault structures in southern Kerman province do appear to be active in the late Quaternary and may be capable of producing destructive earthquakes in the future. This study shows how widely available remote sensing data can be used to provide information on the distribution of active faulting across large areas of deformation.

Quaternary elevation change of the Gulf of Corinth in central Greece

Dramatic elevation changes have occurred since early Pleistocene time in and around the Gulf of Corinth sedimentary basin in central Greece, which is actively extending at a maximum rate of ca . 2 mm a -1 . Shoreline deposits younger than 1 million years are found at up to ca . 1200 m elevation south of the Gulf, with sediment from an older Plio-Pleistocene basin above 1750 m. The Gulf floor, in the hanging-wall of normal faults along its southern coast, has subsided up to ca . 1650 m on the same timescale. However, other hanging-wall localities such as the Corinth isthmus - east of the Gulf - have uplifted instead. During the past million years the Gulf has alternated between marine and lacustrine environments in response to glacially induced sea-level variations. This study establishes its chronology of marine and lacustrine terraces for the past half million years, allowing lateral variations in uplift to be investigated. To explain the observed elevation changes, it is suggested that ca . 0.9 million years ago the previously lacustrine Gulf became flooded by ca . 80 m during an interglacial marine highstand. The resulting ca . 0.8 MPa increase in lithostatic pressure at the base of the brittle upper crust caused southward lower-crustal flow to beneath the older Plio-Pleistocene basin. Isostatic adjustment uplifted this basin, creating unstable topography that enabled rapid erosion. This lower-crustal flow, which since been maintained by the sediment load in the Gulf that results from this erosion, also causes the hanging-wall uplift of the Corinth isthmus and other ‘anomalous’ localities. The Gulf of Corinth is thus an important case study locality for revealing the existence of lower-crustal flow during continental extension.