Mountain Front Research Articles

Role of transverse structures in paleoseismicity and drainage rearrangement in rift systems: the case of the Valdecebro fault zone (Teruel graben, eastern Spain)

The E–W trending, nearly pure extensional Valdecebro fault zone is a transverse structure at the central sector of the N–S Teruel graben. It was activated by the Late Ruscinian (Early Pliocene, ca. 3.7 Ma), giving rise to structural rearrangement of the graben margin. Until the Late Pleistocene, it has accommodated a net slip ca. 205 m, with slip rate of 0.055 mm/a. Paleoseismicity has been analysed in a 29-m-long, 5-m-deep trench excavated through a fault branch that offsets a Pleistocene pediment surface. The paleoseismic succession includes a minimum of 6–7 events occurred since ca. 142 ka BP, although a model with 12 events could be more realistic. The following paleoseismic parameters have been inferred, assuming a minimum of 6 and a maximum of 12 events: average coseismic slip = 58–117 cm; recurrence period = 8.4–28.4 ka; potential moment magnitude Mw = 5.8–5.9. The recorded displacement since ca. 142 ka BP totalizes 7.0 m, with slip rate of 0.05–0.07 mm/a. Slip on the transverse Valdecebro fault zone has critically contributed to bulk deformation under a prevailing ‘multidirectional’ extensional regime. Drainage patterns have been rearranged, recurrently switching between westward and southward directions as a consequence of diverse slip episodes at the Valdecebro fault zone (E–W) and the neighbouring La Hita (N–S) and Concud (NW–SE) faults. The ultimate westward drainage of the Valdecebro depression incised and dismantled a southward-sloping Pleistocene pediment sourced at the Valdecebro mountain front, representing a capture by the Alfambra river occurred between 124 and 22 ka BP.

Beryllium-10 dating of the Foothills Erratics Train in Alberta, Canada, indicates detachment of the Laurentide Ice Sheet from the Rocky Mountains at ~15 ka

AbstractThe Foothills Erratics Train consists of large quartzite blocks of Rocky Mountains origin deposited on the eastern slopes of the Rocky Mountain Foothills in Alberta between ~53.5°N and 49°N. The blocks were deposited in their present locations when the western margin of the Laurentide Ice Sheet (LIS) detached from the local ice masses of the Rocky Mountains, which initiated the opening of the southern end of the ice-free corridor between the Cordilleran Ice Sheet and the LIS. We use 10Be exposure dating to constrain the beginning of this decoupling. Based on a group of 12 samples well-clustered in time, we date the detachment of the western LIS margin from the Rocky Mountain front to ~14.9 ± 0.9 ka. This is ~1000 years later than previously assumed, but a lack of a latitudinal trend in the ages over a distance of ~500 km is consistent with the rapid opening of a long wedge of unglaciated terrain portrayed in existing ice-retreat reconstructions. A later separation of the western LIS margin from the mountain front implies higher ice margin–retreat rates in order to meet the Younger Dryas ice margin position near the boundary of the Canadian Shield ~2000 years later.

Evaluation of relative tectonic activity along the Priene-Sazlı Fault (Söke Basin, southwest Anatolia): Insights from geomorphic indices and drainage analysis

The West Anatolia Extensional Zone, which has a width of about 300 km, is located within the Alpine-Himalayan belt and is one of the regions with intense seismic activity in the world. The most important geomorphological structures in this area are three main graben structures resulting from regional N-S extension since the Early Miocene. These structures are the E-W trending Buyuk Menderes, Kucuk Menderes, and Gediz grabens. Soke Basin is located at the SW end of the Buyuk Menderes graben. The lineaments which control the NW of Soke Basin have a length of approximately 40 km and have been defined as the Priene-Sazli Fault (PSF). The PSF is seismically active, and the last large earthquake (the Soke-Balat earthquake; Ms: 6.8) was produced on July 16th of 1955. The ancient city of Priene, which was located in the study area, suffered from destructive earthquakes (in the 4th century and 2nd century BC, in the 2nd century AD, during the Byzantine period and after the 12th century BC). This study aims to reveal the effect of the PSF on the morphotectonic evolution of the region and the relative tectonic activity of the fault. To this end, it was the first time the stream length gradient index (SL: 130–1303), mountain-front sinuosity (Smf: 1.15–1.96), valley floor height and valley width ratio (Vf: 0.27–1.66), drainage basin asymmetry (AF: 0.15–0.76), hypsometric curve (HC) and hypsometric integral (HI: 0.22–0.86) and basin shape index (Bs: 1.04–5.75) along the mountain front that is formed by the PSF. Using a combination of the mountain-front sinuosity (Smf), valley floor height and valley width ratio (Vf), it is found that the uplift ratio in the region is not less than 0.05 mm/yr and the relative tectonic activity of PSF is high. According to the relative tectonic activity index (Iat) obtained from geomorphic indices, the southwest part of the PSF is relatively more active than the northeast part. As a result, I posit that the PSF has the potential to produce earthquakes in the future similarly to those that were produced in the past, and that the most destructive earthquakes will likely occur on the southwest segments of the fault according to geomorphic indices.

Long‐Period Rayleigh Wave Phase Velocity Tomography Using USArray

AbstractSeismic models show that the shallow mantle beneath the contiguous United States is characterized by low velocities west of the Rocky Mountain Front, high velocities beneath the North American craton, and moderate wave speeds along the eastern seaboard. However, numerous questions remain, including the distribution of temperature and partial melt in the mantle that may explain the slower velocities in the west; the origin and depth extent of the western edge of the cratonic lithosphere; and explanations for slower velocities observed along the eastern seaboard. To investigate these questions, we have measured teleseismic Rayleigh wave phase and amplitude at USArray stations for periods of 25–180 s and calculated phase velocity using the Helmholtz tomography method. Notably, the new long‐period maps represent an opportunity to resolve mantle structure at sublithospheric depths and show differences relative to shorter periods in both the distribution of slow velocities in the west and the extent of fast velocities in the central United States. The maps are then used as a basis for comparing six recent 3‐D shear velocity models of the contiguous United States, from which we predict phase velocities. While predictions from surface‐wave models agree best with our observations at short and intermediate periods, the longest‐period maps are most similar in amplitude to body‐wave models.

Evaluation of Groundwater Levels in the Arapahoe Aquifer Using Spatiotemporal Regression Kriging

AbstractGroundwater monitoring is fundamental to understanding system dynamics, trends in storage, and the long‐term sustainability of an aquifer. Water‐level data are the key source of information used to understand the response. However, groundwater‐level data are often irregularly sampled, leading to temporal gaps in the record, and are not adequately distributed spatially across an aquifer. This presents challenges when spatially interpolating potentiometric surfaces and creating groundwater maps due to data availability. We present a spatiotemporal kriging methodology to improve spatial and temporal confidence in groundwater‐level predictions at unsampled locations. The space–time data set consists of a trend and residual component modeled with a linear regression and utilize a sum‐metric model to represent spatiotemporal covariances. The Arapahoe aquifer is used as a case study to demonstrate the benefits of spatiotemporal kriging over spatial kriging across a sparsely gauged and irregularly sampled aquifer. The Arapahoe aquifer is a major source of water for many residents along the Rocky Mountain Front Range in Colorado. The results show superior performance of spatiotemporal kriging to predict groundwater levels over the traditional spatial kriging. Spatiotemporal kriging represents realistic temporal and spatial changes in water levels and avoids some of the problems inherent to spatial kriging. This study demonstrates the power of spatiotemporal kriging to help inform system dynamics in irregularly sampled aquifers.

Investigating topographic metrics to decipher structural model and morphotectonic evolution of the Frontal Siwalik Ranges, Central Himalaya, Nepal

The fold-and-thrust belt in the Himalayan front is marked by the upliftment of the Frontal/Outermost Siwalik Hills along the Main Frontal Thrust (MFT). These frontal ranges display distinct morphology with prominent curved/stair-stepped and overlapping segments in the central Himalaya. In this study, we analyse the structural framework, morphology, growth and relative uplift rates of the frontal ranges in the central Himalaya, using various topographic metrics. The results suggest that the frontal ranges are folds developed along six MFT segments that have interacted to form the present day topography. These segments are also overlapping in some areas, thus, resulting in stress partitioning. We also identify a NW-SE trending pre-existing tear fault in the region that forms barrier to the growth and propagation of the MFT segments and the frontal ranges along it. The uplift rates are generally lower on relatively older fault segments due to initiation of the younger overlapping faults. It is supported by the results of the morphometric indices as the older and less active MFT segments yield high mountain front sinuosity ratio (1.3–2.2) and valley floor width to height ratio (3.3–14.6), and low values of steepness index (0.2–0.8) and hypsometric integral (0.4–0.5). Growing folds along the MFT segments have resulted in the deflection of the Narayani and the East Rapti rivers. We establish a model for the initiation and growth of various structural segments in the study area and the resultant drainage reorganisation.

The relationship between Cenozoic shallow igneous bodies and thrust systems of the mountain front of the Cordillera Principal, Mendoza province, Argentina

Within the Malargüe fold and thrust belt, located in the southern Central Andes, south of Mendoza province, Argentina, several shallow intrusive bodies which are part of an extensive Neogene magmatism are exposed and linked to the subduction of the Nazca plate beneath the western edge of South America. This study attempts to establish the relationship between these igneous bodies and thrusts that are part of fault systems that built the Andean orogen. It is interpreted that these thrusts have acted as feeding channels for the ascent of magma and therefore there is a direct link between the distribution of magmatism and fault systems. The igneous bodies are emplaced through low-angle faults and it results in longitudinal strips of intrusive bodies of younger ages towards the Andean foreland. The petrographic and geochemical analysis shows that the sills, dikes and laccoliths, outcropping in the Malargüe fold and thrust belt, have a calc-alkaline affinity indicating an origin related to the Andean magmatic arc. The evolutionary model of the emplacement of the intrusive bodies and their relationship with the Andean thrust systems has significant implications for geotectonic models that consider the shifting of the magmatic sources of the Andean Arc currently proposed for these regions of the Andes.

Quantifying vertical movements in fold and thrust belts: subsidence, uplift and erosion in Kurdistan, northern Iraq

Abstract Traditional structural analysis in fold and thrust belts has focused on quantifying horizontal movements. In this paper, the importance of quantifying vertical movements is illustrated using a case study from Kurdistan, northern Iraq. The subsidence history of this area can be determined by analysis of the stratigraphic record from deep exploration wells. A phase of thermal subsidence from Middle Permian to Late Cretaceous (tectonic subsidence 1.8–1.9 km) was followed by flexural subsidence in the Late Cretaceous and Cenozoic (tectonic subsidence >0.6 km) in response to the closure of the Neo-Tethys Ocean. The main phase of continental collision during the Neogene resulted in the development of the Zagros fold and thrust belt; the amount of uplift at individual anticlines can be estimated from their amplitude (up to 3 km), but regional cross-sections indicate that approximately 1 km of additional basement-involved uplift is present NE of the Mountain Front. The timing of basement-involved uplift is interpreted to be coeval with the deposition of a Pliocene–Quaternary growth sequence adjacent to the Mountain Front. The amount of erosion resulting from the uplift can be estimated from vitrinite reflectance and cross-sections; these estimates show a similar pattern, with maximum erosion in the mountains NE of the Mountain Front (>1.5 km) and lesser erosion in the adjacent foreland basin (generally <0.8 km). The results provide a quantitative understanding of subsidence, uplift and erosion, and have been used to define prospective and high-risk areas for petroleum exploration.

Application of the Fisher Optimal Segmentation Method in MT Interpretation: A Case Study from Qiangtang Basin, Qinghai -Tibet Plateau

The development and construction of thrust faults in mountain front areas are quite complicated, causing interpretation difficulties with electrical resistivity. To address these difficulties, an optimal stratification method involving magnetotellurics (MT) was applied, based on Fisher's clustering method for continuous data. The feasibility and effectiveness of this method are verified by applying it to the MT exploration data in Qiangtang Basin, Qinghai-Tibet Plateau, China. The results show that the optimal stratification method can improve the resolution of the resistivity model effectively in areas with complex structures. The MT inversion section after optimal stratification reflects the stratum interface, fault and structure style more directly and can be used for comparison with seismic data. The Fisher segmentation method can be applied to the interpretation of the MT data as a supplementary method, especially in the complicated structural belts, areas in which the geological structure and deformation information cannot be recognized effectively by conventional methods.

Drainage Characteristics of Tectonically Active Area: An Example from Mawar Basin, Jammu and Kashmir, India

Abstract Geomorphic and neo tectonic studies have been carried out for the first time in Mawar basin of the Kashmir valley. On the basis of field investigations and geomorphic data derived from toposheets and satellite imageries, with the help of Arc GIS (10.3) and Global Mapper (18) the relationship between morphology and tectonics has been investigated in Mawar basin, which lies to the northwest of Kashmir valley. The morphotectonic aspects like mountain front sinuosity (Smf), hypsometric integral (Hi), have been studied to relate the tectonic forces with erosive power and identify the areas where field investigations are required. The field interpretation indicates that the landforms of the area are structurally controlled and mainly consist of tectonic linear, parallel striking ridges and valleys. The course of Mawar is mostly controlled by the Mawar fault striking east–west and local structures present in the area. General morphometric parameters like assymetry factor (Af), transverse topography symmetry (T), stream length gradient (SL) and valley floor width to height ratio (Vf) have been computed to draw the conclusion of tectonic activity on the drainage. The Af and T suggest that the basin has shifted to the right side and the Mawar river has shifted to the left side when facing downstream. The SL values indicate that the river has fluctuations in gradient/knickpoints at 6.8, 10 and 18 km from the source. However the Vf values infer the basin has deeply incised V-shaped valleys. All the quantified geomorphic indices and their interrelationship with the geomorphology are useful in comparing different drainage basins in terms of tectonic character and are helpful in delineating the areas where more detailed works will be fruitful. The results of computed geomorphic indices, geomorphology and the structures present in the Karewas (Plio Pleistocene) deposits inferred that the basin has shown activity in Pleistocene period, suggesting the basin is tectonically active.

The 12 November 2017 Mw 7.3 Ezgeleh‐Sarpolzahab (Iran) Earthquake and Active Tectonics of the Lurestan Arc

AbstractThe 12 November 2017 Mw 7.3 Ezgeleh‐Sarpolzahab earthquake is the largest instrumentally recorded earthquake in the Zagros Simply Folded Belt by a factor of ∼10 in seismic moment. Exploiting local, regional, and teleseismic data and synthetic aperture radar interferometry imagery, we characterize the rupture, its aftershock sequence, background seismicity, and regional tectonics. The mainshock ruptured slowly (∼2 km/s), unilaterally southward, for ∼40 km along an oblique (dextral‐thrust) fault that dips ∼14°E beneath the northwestern Lurestan arc. Slip is confined to basement depths of ∼12–18 km, resolvably beneath the sedimentary cover which is ∼8 km thick in this area. The gentle dip angle and basement location allow for a broad slip area, explaining the large magnitude relative to earthquakes in the main Fars arc of the Zagros, where shallower, steeper faults are limited in rupture extent by weak sedimentary layers. Early aftershocks concentrate around the southern and western edges of the mainshock slip area and therefore cluster in the direction of rupture propagation, implying a contribution from dynamic triggering. A cluster of events ∼100 km to the south near Mandali (Iraq) reactivated the ∼50° dipping Zagros Foredeep Fault. The basement fault responsible for the Ezgeleh‐Sarpolzahab earthquake probably accounts for the ∼1 km elevation contrast between the Lurestan arc and the Kirkuk embayment but is distinct from sections of the Mountain Front Fault that define frontal escarpments elsewhere in the Zagros. It may be related to a seismic interface underlying the central and southern Lurestan arc, and a key concern is whether or not the more extensive regional structure is also seismogenic.

Longitudinal profiles and geomorphic indices analysis on tectonic evidence of fluvial form, process and landform deformation of Eastern Himalayan Rivers, India

ABSTRACTThe drainage pattern and the morphology of the piedmont zone of the Himalayas are clear indicators of the active orogenic belt of most recent origin formed by the collision of Indian and Eurasian plate. The foothills of the Himalayas in West Bengal are zones of active tectonics drained by the rivers belonging to the Brahmaputra system. The present study is conducted for the left bank tributaries and sub-tributaries of Tista which bear the imprint of active tectonics of the region as they lie in the zone of Himalayan Frontal Fault, the most active thrust belt of Himalayas. Data and subsequent field experiences which showed that the region is constantly acted upon by recent diastrophism. Various tectonic indices were calculated to evaluate the evidence of tectonism. This include hypsometric integral (HI), fractal dimension (FD), basin asymmetry factor (AF), basin shape index (Bs), stream-length gradient (SL), mountain front sinuosity (Smf) and valley-floor width to valley height ratio (Vf). The results of these indices are used to prepare an index of active tectonics with three classes which is represented in a map. Then the field evidences of deformed landscape are matched with the areas showing high tectonic index values.

Late Quaternary deformation in parts of the Belt of Schuppen of Dimapur and Peren districts, Nagaland, NE India

Geomorphic evidences and geochronology suggest recent tectonic activity in the Belt of Schuppen of Dimapur and Peren districts of Nagaland. Multiple levels of strath terraces forming remarkable geomorphic expressions are observed along the Chathe and Jharnapani river valleys. They indicate episodic uplift of the hanging‐wall blocks of the thrust systems. The major lineaments prominently trend parallel to the NE–SW regional thrusts, some being perpendicular or oblique. Active normal faults displacing bedrock and overlying fill sediments point to recent tectonic activity. The parallel and trellis drainage patterns are lineament‐controlled. Uplift of the terrain is evident from successive palaeochannels of the Chathe River younging towards the southwest. Three major aggradational phases of the terrace sediments are inferred from optically stimulated luminescence (OSL) chronology, the oldest beginning around 21 ka, the second around 11–7 ka, and the youngest between 3.5 and 1 ka. A sand lens of a tilted strath terrace exposed between Kukidolong and Chumukedima is dated at 7 ka, indicating tectonic events after 7 ka. Five major phases of bedrock uplift/incision have been estimated during 20 ka (0.13 mm/year), 11 ka (0.92 mm/year), 9 ka (2.29 mm/year), 6 ka (0.67 mm/year), and 1.8 ka (2.6 mm/year). Transverse topographic symmetry and asymmetry factor data suggest tilting towards the NE and SW. Other morphometric indices, such as channel sinuosity, stream length gradient index, valley floor to valley height ratio, and mountain front sinuosity, suggest that the area is tectonically active, which corroborates field observations.

Dynamic and geomorphic characterizations of the Mocoa debris flow (March 31, 2017, Putumayo Department, southern Colombia)

On the night of March 31, 2017, a rainfall-induced landslide event with more than 600 shallow landslides was triggered in Mocoa (Putumayo Department, southern Colombia). These landslides and the subsequent Mocoa Debris Flow (MDF) event caused, according to data published from the Unidad Nacional para la Gestion del Riesgo de Desastres (UNGRD, disaster risk management government agency), a catastrophic aftermath where 333 people were killed (including at least 118 children), 398 people were injured, and 76 people are still missing. In order to unravel the kinematic aspects of the MDF formation and the geomorphic setting which conditioned debris flow and landslide formation, high-resolution drone and satellite imagery, geomorphic indices, landslide inventory, and rainfall data from the event were analyzed. Flow discharge and velocity calculations associated to the MDF were calculated using three different methodologies which showed that the flow acquired a volume of ~ 2.6 × 106 m3 and an average velocity of 8–12 m/s, while the landslides developed in the Taruca, Taruquita, Mulato, and Sangoyaco basins contributed an estimated volume of about 298,000 m3. A landslide volume of about 3.44 × 106 m3 of material was calculated, from which less than 10% feed the MDF. Heavy rainfall and antecedent rainfalls were the triggering factors associated to shallow landslides developed on granitic rocks from the Mocoa monzogranite. Mass movements developed in residual soils from sedimentary rocks are more related to poor vegetation cover and intense anthropic activity such as extensive farming and deforestation. The recent activity of La Tebaida–Mocoa Fault and exhumation of the Mocoa monzogranite are considered as the main contributors to hillslope instability and landslide susceptibility. An active tectonic mountain front, steep slopes, and high drainage gradients are common at the study basins and are the key features controlling erosion and sedimentation rates. In this document, a brief introduction to the climatic, geological, and geomorphological characteristics of the involved basins and kinematic behavior of the MDF are presented.

SWB Modeling of Groundwater Recharge on Catalina Island, California, during a Period of Severe Drought

This study applied a soil water balance (SWB) model to simulate groundwater recharge on Catalina Island, California, for the years 2008–2014, a period that coincided with a severe drought. Island-wide average recharge ranged from 0.05 mm/year in 2013 to 82.3 mm/year in 2008, with a 7-year mean of 23.0 mm/year. High recharge is primarily associated with east-facing mountain fronts and the land cover types “developed, open space” and “herbaceous”. This spatial trend is also reflected in recharge estimates for groundwater well locations produced by the Cl mass balance method. Only in 2008 did all areas of the island experience recharge, while the recharge was very low during the drought years 2009 and 2012–2014. Sensitivity analyses indicate an unresolved discrepancy in land cover classification (i.e., herbaceous grass dominated vs. chaparral and coastal sage dominated) to be a significant factor. In a scenario where herbaceous grass dominates, as field studies from the early 1980s imply, recharge estimates nearly double. Nevertheless, the overall low recharge rates presented herein and the fact that drought conditions in Southern California have worsened since 2014 suggest that large parts of the island may not have received any recharge in nearly a decade.

Evaluate Tectonic Activity of Tehran City (Iran) Based on Geomorphic Indices, Field Investigation and Remote Sensing Study

Active tectonics in the south part of Alborz Mountain (Iran) has greatly influenced the drainage system and geomorphic expressions. The metropolis of Tehran is located at the southern foothills of the Alborz Mountains at the abrupt topographic boundary between the mountain range and the northern border of the central Kavir Desert. The presence of active faults and tectonic activity, threatens the area and shows the vulnerability of this Tehran city. So the evaluation of active tectonics of Tehran City is necessary because of vast human activity, which has hidden geomorphic feature. Active tectonics of Tehran City was evaluated by using Digital elevation model (DEM) derived drainage network and three geomorphic indices basin (asymmetry factor (AF), basin shape index (Bs) and mountain front sinuosity (Smf)). The average of the three measured geomorphic indices was used to evaluate the distribution of relative tectonic activity in the study area. Furthermore to overcome some inevitable error in this method, field investigation was carried out also remote sense was studied, and finally the obtained results were compared with existing seismic data. The result confirms that the East South, East North and West North Tehran have high rate of relative tectonic activity (RTA) respectively.

The 3‐D Structural Model of an Out‐of‐Sequence Earthquake in China: Implication for the Reactivation of Positive Inversion Structures Along the Northern Tianshan Fold‐and‐Thrust Belt

AbstractThe intracontinental earthquake behavior is not well understood due to its complexity in the interior of the continent. The Tianshan Mountain is located in the interior of the Eurasian plate, which was rejuvenated in the Cenozoic due to the India‐Asia collision and sourced several large earthquakes. The 2016 Hutubi earthquake occurred within the northern Tianshan, China, during rupture of a high‐angle back‐thrust toward the hinterland, which broke the long‐time quiescence in the mountain front. The geometry, dynamics, and hazard implications of this earthquake on an out‐of‐sequence thrust fault remains unclear. The 3‐D structural model shows that the coseismic fault is connected to the large‐scale blind Southern Junggar thrust, which sourced the 1906 Mw ~8 Manas earthquake. The geometry of the coseismic fault and the occurrence of extensional tectonics in the Jurassic suggest that the Hutubi earthquake occurred on a reactivated rift‐related structure. To test this hypothesis and study the kinematics, we performed sandbox modeling, with results suggesting that coseismic fault can form during positive inversion of a preexisting Jurassic rift, and that the Southern Junggar thrust and related structures may be recently active. Coal beds facilitated the transfer of fault slip and strain from mountain to basin and from basal to roof detachment. We propose that the preexisting rift and related sedimentation controlled the subsequent structure and geomorphology of the mountain belt through thrust wedge formation. This study provides a typical example for the study of intracontinental inversion structure and its earthquake behavior.

Geology and Active Tectonics of the Lalmai Hills, Bangladesh–An Overview from Chittagong Tripura Fold Belt Perspective

The Lalmai Hills is a low amplitude anticline with significant variations in landforms, situated along the western fringe of the Chittagong-Tripura Fold Belt (CTFB) and immediate east of the Indo-Burmese deformation front. This fold belt of the Bengal Basin along with more easterly Indo-Burman Range (IBR) developed as a consequence of the oblique collision between Indian and Burmese plates. This neotectonic activity is still continuing and shaping the geomorphology of the area. This study is conducted based on the geomorphological observation of the topo maps and satellite images, and through reconnaissance field work. Stream length gradient index (SL Index) and Mountain front sinuosity (Smf) reveals the relative status of tectonic activity. Anomalous SL index values confirm the position of the sympathetic minor faults and also relate to the local stratigraphy. A 2D structural model based on the seismic section reveals thrusts controlled wedge-shape upliftment of the central part as pop-up anticlinal structure. The western thrust is the direct result of the collision of the Indian and Burmese plates, and the eastern one is the back thrust of the western fault. Low Smf value found in the western flank signifies recent tectonics and relatively high Smf value in the eastern flank indicates that weathering intensity is relatively greater compared to western flank. Finally, the findings not only enhanced the understanding of geomorphic evolution and active tectonics of the Lalmai Hills area but also the overall tectonic and geomorphic evolution of the western most folded part of the CTFB.

Late Wisconsinan Cordilleran and Laurentide glaciation of the Peace River Valley east of the Rocky Mountains, British Columbia

In the past, researchers have disagreed over the maximum extent of the Cordilleran Ice Sheet in the Peace River valley during the Late Wisconsinan. Some workers argued that Cordilleran ice reached beyond the Rocky Mountains and briefly coalesced with the Laurentide Ice Sheet on the westernmost Interior Plains. In contrast, others asserted that Cordilleran ice did not reach beyond the eastern front of the Rocky Mountains. Stratigraphic interpretation of three sections within a Middle Wisconsinan paleovalley and re-examination of a previously published regional stratigraphic framework show that western-sourced ice (likely the Cordilleran Ice Sheet) extended east of the mountain front during the Late Wisconsinan, prior to the incursion of the Laurentide Ice Sheet into the area. This conclusion has implications for Cordilleran Ice Sheet reconstruction and modelling, and provides insight into the interactions between the Cordilleran and Laurentide ice sheets during the last glaciation.

Cement characteristics and effects on dolomite reservoir pores in the fourth member of Leikoupo Formation, Longmen Mountain front, western Sichuan Basin

Cement characteristics and effects on dolomite reservoir pores in the fourth member of Leikoupo Formation, Longmen Mountain front, western Sichuan Basin