Cuesta Ridge Research Articles

The Present-day Landscape of Bukit Keluang Formation: Geoheritage Potential for Conservation and Geotourism

The Late Permian sedimentary rock of Bukit Keluang Formation is well exposed on three isolated hills namely the Bukit Keluang, Bukit Bubus and Bukit Dendong. The consecutive hills exhibit a unique landscape of linear ridge surrounded by the alluvial plains and are well known for their beautiful sandy beaches and outstanding landscapes. Geological landscape in the area falls into three heritage value set (scientific, aesthetic and recreational value) that in need of immediate conservation. Scientific evidence shows that the study area exhibits a unique lithologically and structurally controlled landscape characterised by first order topography of folded and thrusted sequence (anticlinal hill), linear cuesta ridge and denudation hill. Differential erosion of the conglomerate-sand-shale sequences led to the development of linear ridge with different elevation profiles. The geometric and geographic position of the hills conforms with the regional structural trend in the area with the N-S trending fault system is inferred as the major fault that displaced the Bukit Keluang Formation. Internal complexities in the individual structures in the form of cross-faults, oblique-faults and lineaments trending NW-SE, NE-SW to N-S directions have formed cave morphological feature and divide the hills into separate blocks. The geological landscape also contributes to an aesthetic value such as the beautiful hilly landscape and sandy beach, while recreational values including hiking, mountain biking and water activities. Geological heritage and geotourism could have a positive future in Bukit Keluang, Bukit Bubus and Bukit Dendong. The in-situ and ex-situ geological conservation is urgently needed in order to support the efforts to implement geoscience knowledge to the public.

Analisis Multi Raster SRTM, Radarsat dan Landsat untuk Karakterisisasi Morfo-struktur dari Geometri Sesar di Daerah Binuang, Kalimantan Selatan

The Binuang area and its surroundings are genetically structural landforms which characterized by cuesta ridge line with curve lineaments pattern on northeast-southwest direction. Geomorphological approach were carried out to determine structural geometry of geological surface using qualitative and quantitative approach on multiple map analysis of remote sensing data. The result of quantitative analysis on elevation data are used to classify heights, slope shape and steepness, lineaments, drainage, and slope aspect. Optical images were classified to determine lithological pattern and boundaries through analysis of band ratios, decorrelation stretch, principal component, and spatial enhancement. The research area are classified into eight class of structural landforms, depicting deformations that occured in western flank of Meratus Mountains. The surface pattern indicates the influence of compressional stress, shown by fold belt with longitudinal characteristic and fault-bounded anticlines on northeast-southwest axis. The formation of main structure pattern on research area was compared with that on strike-slip fault analog model. The resulting correlation factor, R=0.932, shows that both of them are highly correlated. In conclusion, surface structure can possibly form another variation of thrusted mountain belt, such as thrust-dominated restraining bends.Keywords: landsat, SRTM, morphostructure, morphometry, rhomboidal pattern, Meratus.

Analisis Multi Raster SRTM, Radarsat dan Landsat untuk Karakterisisasi Morfo-struktur dari Geometri Sesar di Daerah Binuang, Kalimantan Selatan

The Binuang area and its surroundings are genetically structural landforms which characterized by cuesta ridge line with curve lineaments pattern on northeast-southwest direction. Geomorphological approach were carried out to determine structural geometry of geological surface using qualitative and quantitative approach on multiple map analysis of remote sensing data. The result of quantitative analysis on elevation data are used to classify heights, slope shape and steepness, lineaments, drainage, and slope aspect. Optical images were classified to determine lithological pattern and boundaries through analysis of band ratios, decorrelation stretch, principal component, and spatial enhancement. The research area are classified into eight class of structural landforms, depicting deformations that occured in western flank of Meratus Mountains. The surface pattern indicates the influence of compressional stress, shown by fold belt with longitudinal characteristic and fault-bounded anticlines on northeast-southwest axis. The formation of main structure pattern on research area was compared with that on strike-slip fault analog model. The resulting correlation factor, R=0.932, shows that both of them are highly correlated. In conclusion, surface structure can possibly form another variation of thrusted mountain belt, such as thrust-dominated restraining bends.Keywords: landsat, SRTM, morphostructure, morphometry, rhomboidal pattern, Meratus.

Analisis Multi Raster SRTM, Radarsat dan Landsat untuk Karakterisisasi Morfo-struktur dari Geometri Sesar di Daerah Binuang, Kalimantan Selatan

The Binuang area and its surroundings are genetically structural landforms which characterized by cuesta ridge line with curve lineaments pattern on northeast-southwest direction. Geomorphological approach were carried out to determine structural geometry of geological surface using qualitative and quantitative approach on multiple map analysis of remote sensing data. The result of quantitative analysis on elevation data are used to classify heights, slope shape and steepness, lineaments, drainage, and slope aspect. Optical images were classified to determine lithological pattern and boundaries through analysis of band ratios, decorrelation stretch, principal component, and spatial enhancement. The research area are classified into eight class of structural landforms, depicting deformations that occured in western flank of Meratus Mountains. The surface pattern indicates the influence of compressional stress, shown by fold belt with longitudinal characteristic and fault-bounded anticlines on northeast-southwest axis. The formation of main structure pattern on research area was compared with that on strike-slip fault analog model. The resulting correlation factor, R=0.932, shows that both of them are highly correlated. In conclusion, surface structure can possibly form another variation of thrusted mountain belt, such as thrust-dominated restraining bends.Keywords: landsat, SRTM, morphostructure, morphometry, rhomboidal pattern, Meratus.

Landslides and Fortified Settlements as Valuable Cultural Geomorphosites and Geoheritage Sites in the Moldavian Plateau, North-Eastern Romania

Today, as in the past, people living in hilly and mountainous regions have had to face the consequences of mass movement processes. Archaeological remains are important elements of cultural heritage, which can be significantly affected by landslides in different environmental settings and landscape evolution phases. In the Eastern Carpathians lowlands, landslides have shaped a landscape with inaccessible escarpments tens of metres high, providing ancient populations with naturally defensive sites at which to build their fortified settlements. In this study, we present a unique geoarchaeological context, the case of Chalcolithic and Thraco-Getic (6.5 ka BP to 2500 BP) fortified settlements, for which landslides provided a favorable geomorphologic setting for their construction. At the same time, however, landslides reamin as a permanent threat to the archaeological sites. In the Moldavian Plateau, North-Eastern Romania, more than 35 sites were identified on structural plateaus bounded by wide scarps of Pleistocene to Lower Holocene landslides, on cuesta ridges bounded by scarps of Holocene landslides, or situated on hillslopes, on erosional remnants of very old landslide bodies. For nine out of the 35 sites, we discuss and evaluate the geomorphosite status according to an indirect method developed by mixing a variety of methodologies illustrated in the literature, and we classify them as geomorphosites and specifically as cultural geomorphosites. The complex geomorphological, paleogeographical, and archaeological value of these proposed geosites allow us to argue for their geoheritage status. This situation requires a detailed analysis of landslide hazard and risk for these sites, since some have already been affected by landslides in the past, and especially when considering possible protection measures and actions to preserve and to include these geoheritage sites in the geotouristic networks of North-Eastern Romania.

The Corossol Structure: a glaciated crater of possible impact origin in the northwestern Gulf of St Lawrence, eastern Canada

The majority of confirmed impact craters on Earth have been discovered on land. However, the increased use of high-resolution, full-bottom-coverage seafloor mapping methods such as multibeam bathymetry have enabled the discovery of previously unknown subaqueous impact craters on continental margins and in large lakes. High-resolution bathymetric and sub-bottom profiler data collected south of the city of Sept-Iles in the northwestern Gulf of St Lawrence, eastern Canada (Fig. 1a), revealed a previously unreported circular structure of possible impact origin located 20 km off the mainland in water depths of 40–208 m (Fig. 1b, c) that had been overrun by the Laurentide Ice Sheet (Lajeunesse et al. 2013). Fig. 1. The Corossol Structure, northwestern Gulf of St Lawrence, eastern Canada. ( a ) Location of study area (red box; map from GEBCO_08). ( b ) The Corossol Structure from an oblique view. ( c ) The structure is delimited to the north by series of cuesta ridges. Streamlined glacial lineations and till on its surface indicate …

Structural Control on Landscape Development of Barak Valley, Northeast India

Abstract: The Barak Valley, comprising a contiguous region of three south Assam districts of Cachar, Hailakandi and Karimganj, represents a ridge and valley province with meridional to sub-meridional anticlinal hills and synclinal valleys. Thin skinned tectonics resulted in the deformation of Neogene clastics which is manifested in the form of a series of anticlines and synclines. These structural elements have profound control on the development of present-day landscape in Barak valley. Structurally controlled fluvial erosion produced a series of cuesta ridges and strike valleys which were further subjected to erosional dissection leading to development of numerous topographic highs. Along the northern part of Barak valley adjoining Barail range, three terrace levels stand out with topographic offsets of upto ~10 m. These terraces are linked to tectonic adjustments along Haflong-Disang Thrust that traverse along the Barail foothills. Numerous wetlands linked to fluvial activities and also isolated from the fluvial domain form a significant element of the Barak valley landscape. Some of these wetlands have their origin to tectonic activities of the region. While the trunk channel of the region follows a nearly E-W trend, all the major tributaries join it at nearly orthogonal position following the prevailing structural trend.

Petrogenesis of serpentinites from the Franciscan Complex, western California, USA

Serpentinites from the Franciscan Complex of California, USA, were analyzed for their bulk major and trace element compositions, relict mineral (spinel and pyroxene) compositions, and stable isotope (O, H, Cl) compositions with the goal of determining protolith origin and subsequent serpentinizing fluid sources in order to decipher the tectonic setting of serpentinization. We focused on serpentinite bodies found in the Franciscan Complex (west of Cuesta Ridge; south of San Francisco; Tiburon Peninsula; Healdsburg) (n=12). Three samples from Cuesta Ridge (part of the Coast Range ophiolite) were also analyzed for comparison. Serpentinites from Cuesta Ridge have flat to U-shaped chondrite-normalized REE patterns and spinels with Cr# values >0.60 implying a supra-subduction zone origin. In contrast, Franciscan serpentinites west of Cuesta Ridge and Tiburon Peninsula have positive-sloped REE patterns. This depletion in LREE is typical of abyssal peridotites. Most relict spinels have low Cr# values (<0.3) and relict clinopyroxenes from Tiburon Peninsula have high HREE concentrations, also supporting an abyssal origin. Franciscan serpentinite samples from south of San Francisco and near Healdsburg have U-shaped REE patterns and spinel compositions that lie within the forearc peridotite field with some overlap into the abyssal field and are of more ambiguous origin. All samples are high in fluid-mobile elements with remarkable positive Ce and Y anomalies. We speculate that these anomalies may be due to involvement of highly oxidizing fluids resulting in the preferential scavenging of Ce and Y by ferromanganese oxyhydroxides during serpentinization. All samples (except those south of San Francisco) have δ18O values of +5.4 to +7.9‰, typical values for oceanic serpentinites formed via low-T seawater hydration on the seafloor. δD values of all samples are extremely low (−107 to −90‰), likely the result of post-serpentinization, post-emplacement interaction with meteoric water at low temperature. Samples south of San Francisco lie on the San Andreas fault and have high δ18O values (+7.2 to +9.5‰) likely due to low-T interaction with meteoric water at high fluid–rock ratios. Most of the serpentinites have δ37Cl values between +0.2 and +0.9‰, typical values for serpentinites formed by interaction with seawater. Exceptions are those from the San Andreas fault and one sample from Cuesta Ridge with a high δ37Cl value (+1.7‰) possibly from interaction with a slab-derived fluid.

Deglaciation landforms and C-14 chronology of the Lac Guillaume-Delisle area, eastern Hudson Bay: A report on field evidence

This paper presents new field data pertaining to the deglaciation of the Lac Guillaume-Delisle area, aiming to establish its emplacement in time and space between the breaching of the Laurentide Ice Sheet (LIS) over Hudson Bay and the final ice disintegration over Northern Québec and Labrador. The deglaciation of the east coast of Hudson Bay started at 8200cal BP in the south-western sector of the Lac Guillaume-Delisle estuary, when the marine limit was at 271m above sea level (asl). By 8000cal BP, frontal moraines and proximal glacio-marine sediments were deposited in the transverse valleys along the coastal cuesta ridges at a mean elevation of 250m asl. They are associated with a regional topographic pinning event of the western margin of the Quebec-Labrador Ice Sheet (QLIS) on the high coastal relief. At that time, the coastal relief encouraged a change in deglaciation mode from fast calving in the open and deep Tyrrell Sea to a tidewater ice-sheet controlled by the topography. The ice front thereafter retreated eastward under very large and fast crustal unloading where ice-contact deltas fed by short sandar and eskers were deposited between 7900 and 7400cal BP (between 240 and 195m asl), as the ice front was receding inland and lost contact with Tyrrell Sea. A series of deposits and landforms characterize this modification in the sedimentation regime when the ice-sheet margin changed from tidewater to terrestrial. Dating shows that the deglaciation of the western margin of QLIS on land was very fast, i.e. faster than when the front of the ice-sheet was in contact with the Tyrrell Sea. As the fall of the relative sea-level continued, a large volume of paraglacial sediments was deposited in the river valleys making up vast fluvial terraces and deltas between 6500 and 5800cal BP (between 125 and 100m asl). Since then, land emergence has continued at a rate of about 1.3m/century. Downcutting by rivers, post-glacial deltaic sedimentation and shoreline changes still continue today.

Chronostratigraphic Assignment of Volcanopelagic Strata Above the Coast Range Ophiolite

The chronostratigraphic assignments of radiolarian cherts, tuffaceous mudstones and volcaniclastic strata (referred to herein as volcanopelagic succession)' overlying the Coast Range ophiolite in the Coast Ranges of California have been refined on the basis of additional field data and recent revision of the Pessagno and others radiolarian biostratigraphic zonation for the Middle and Upper Jurassic of North America. Revision of this zonation scheme, accomplished through the integration of radiolarian data with ammonite biostratigraphy and geochronometry, has enabled close correlation of radiolarian assemblages in North America, Europe, and Japan. However, major differences still exist in the stage assignments of these assemblages among different zonations. The Pessagno and others scheme is utilized herein to discuss the current chronostratigraphic assignments at five localities in the Coast Ranges: Point Sal, Stanley Mountain, Cuesta Ridge, and Llanada in the southern Coast Ranges, and Black Mountain (Geyser Peak area) in the northern Coast Ranges of California. Stage assignments for volcanopelagic successions in these areas range from uppermost Callovian/lower Oxfordian to upper Tithonian.

Geochemical evidence for the tectonic setting of the Coast Range ophiolite: A composite island arc–oceanic crust terrane in western California

The Middle to Late Jurassic age Coast Range ophiolite (CRO) of California contains two geochemically distinct volcanic rock associations that formed in different tectonic settings. Volcanic rocks from the southern CRO (Point Sal, Cuesta Ridge, Stanley Mountain, Llanada, Quinto Creek, and Del Puerto) and parts of the northern CRO (Healdsburg, Elder Creek) are similar to low-K tholeiites and calc-alkaline rocks of the island-arc suite. The thin volcanic sections of these ophiolite remnants suggest formation by intra-arc rifting. In contrast, volcanic rocks from Stonyford seamount and Paskenta in the northern CRO are transitional subalkaline metabasalts with geochemical characteristics similar to enriched mid-ocean ridge basalts or ocean-island tholeiites. These rocks are associated with Tithonian radiolarian cherts and may be part of the Franciscan Complex. Alternatively, they may represent a change in tectonic setting within the CRO during the Late Jurassic. Regardless, the CRO as currently conceived cannot be considered a single terrane with one mode of origin.

Cretaceous Strike-Valley Sandstones, Northwestern New Mexico: ABSTRACT

Cretaceous sandstone bodies, which are the principal oil reservoirs in the San Juan Basin, have been interpreted as offshore bars related to deposition of the regressive Gallup Sandstone. A detailed outcrop and subsurface study in the northwestern San Juan Basin indicates that these sandstone bodies are strike-valley sandstones in the transgressive marine basal unit which rests unconformably on the Gallup Sandstone and older units. Paleotopography of the pre-Niobrara unconformity consisted of northwest-southeast trending cuestas and intervening strike valleys with local relief of over 100 feet. Cuestas and valleys are related to the subcrop of alternating resistant and non-resistant units in the truncated sequence. Elongate, lenticular sandstone bodies overlying the unconformity occur in strike valleys on the northeast side of cuesta scarps. Individual sandstone bodies, with a maximum thickness of about 50 feet, lap out to the southwest against the cuestas and thin to the northeast by facies change to shale. Younger sandstone bodies extend progressively farther to the southwest. Basal Niobrara sandstones are fine to coarse grained and glauconitic, and contain marine macrofossils. Interbedded and laterally equivalent shales also contain marine fossils, including both benthonic and pelagic forms. The sandstones are characterized by broadly lenticular sets (up to 6 feet thick) of high-angle cross-stratification. Measurements of cross-stratification dip directions at 20 localities indicate transport by currents flowing generally southeastward. These sandstones are best interpreted as nearshore marine sands deposited in strike valleys on the seaward side of cuesta scarps during a general transgression to the southwest. During the transgression, cuesta ridges acted to stabilize temporarily the position of the shoreline, permitting accumulation of sand nearshore while clays were deposited farther offshore to the northeast. Transport of sand was largely in the form of underwater dunes migrating alongshore to the southeast. End_of_Article - Last_Page 349------------