Occurrence Of Conglomerates Research Articles

Discovery of Capitanian (Permian) radiolarians and occurrence of conglomerate in volcaniclastic rocks in the Sumaizuku Unit of the Northern Chichibu Belt in the Kanto Mountains, Central Japan

Discovery of Capitanian (Permian) radiolarians and occurrence of conglomerate in volcaniclastic rocks in the Sumaizuku Unit of the Northern Chichibu Belt in the Kanto Mountains, Central Japan

Groundwater investigation of a coastal aquifer in Brunei Darussalam using seismic refraction

Seismic refraction has been utilized widely in the past to characterize shallow aquifers and subsurface layers. This study applies the method on a water-shed scale to get information on the regional groundwater flow system. Furthermore, the application of seismic refraction for groundwater and hydrogeologic studies has not been done before in Brunei Darussalam. The country of Brunei Darussalam, located in the North of Borneo, uses more than 99% of surface water resources for its industry and public consumption, with the remaining groundwater resources currently unexplored. However, the ever-increasing population and national industrialisation are putting more pressure on Brunei’s water resources. In view of finding new groundwater reserves, we incorporate seismic refraction methods to characterize the local subsurface layers and to delineate the groundwater levels at the Berakas Forest Reserve, located in the North-East of Brunei. The site is chosen based on its surface geological suitability for groundwater reservoirs as well as the occurrence of springs and ephemeral streams in the area. Initial investigations indicate that the near-surface lithology of the study area has good aquifer potential, with the occurrence of conglomerate and sand deposits formed by braided and meandering rivers during late Miocene to Pliocene. We carried out four seismic surveys at strategic locations with different elevations and distances to the sea. The interpreted water table elevations from the velocity-depth profiles are compared with the actual ground elevations of observed springs as well as an ephemeral stream. The interpretations from the velocity profiles were verified using 1D multichannel analysis of surface waves at selected locations. In addition, seismic tomography was used to investigate the capillary fringe zone, indicating the presence of clayey and silty sediments in the saturated and vadose zone. Our interpretations show that the water table varies with topographic elevation and distance from the South China Sea, as the overall flow direction is towards the sea. The hydraulic gradient is calculated to be 0.04. Water samples collected from springs indicate fresh water based on density of 1.00 g/cm3 and chloride content below 150 ppm. However, the shallow aquifer is impacted by low pH values and high sulphate concentrations likely due to local acid sulphate soils present in the study area. No saltwater intrusion is expected which is investigated using the Ghyben–Herzberg relationship.

Tectonic geomorphology: An interdisciplinary study of the interaction among tectonic climatic and surface processes

Tectonic geomorphology is a fast-developing interdisciplinary research field. Different from traditional geomorphology, tectonic geomorphology strongly shifts to quantify the geomorphic processes. The central tenet in tectonic geomorphology is to clarify the interactions among tectonic, climatic, and surface processes, and to provide quantitative descriptions of climate, topography, hydrology, physical and chemical erosion, deposition and rock deformation and their relationships in tectonically active settings. In this review, we first introduce major scientific questions and central concepts, the techniques and methods commonly used in this field, especially the major game-changing dating techniques (e.g., cosmogenic nuclide dating and low-temperature thermochronology) and remote sensing or surveying methods (e.g., LiDAR). Then we present some case studies in the past three decades showing lines of evidence that the interaction among tectonic, climatic, and surface processes can occur in a wide range of temporal and spatial scales, ranging from hours to million-year in time, and from single fault to orogenic belt in space. We also synthesize important progresses in this field toward a better understanding of the topographic evolution of orogenic belts: (1) Tectonic, climatic and surface processes collaborate to shape the landscape such that tectonic activities alone do not necessarily lead to topographic growth. For instance, when erosion and tectonic accretion are in equilibrium, topographic steady state is reached, with no surface uplifting despite on-going tectonic activity. (2) Sedimentary records in range-front basins, such as the increase of deposition rate, or the occurrence of conglomerates, were often used as proxies of tectonic uplift of mountain ranges in early studies. However, sedimentary sequence should be a collective product of tectonic, climatic, and surface processes. These commonly-used proxies for tectonic activity can also be due to climate changes, instead. (3) Tectonics plays a key and leading role in the coupling of tectonic-climatic-surface process; climatic and surface processes influence but do not drive tectonics. (4) Isostatic response to erosion will lead to the rebound of mountain peaks, but the overall effect of erosion is to lower the mean elevation. Thus, uplift due to isostatic rebound is a secondary component of tectonics. Lastly, we outline in brief a list of outstanding scientific questions remaining to be answered in the field.

Accretionary prism–forearc interactions as reflected in the sedimentary fill of southern Thrace Basin (Lemnos Island, NE Greece)

Architecture of the well-exposed ancient forearc basin successions of northeast Aegean Sea, Greece, provides useful insights into the interplay between arc magmatism, accretionary prism exhumation, and sedimentary deposition in forearc basins. The upper Eocene–lower Oligocene basin fill of the southern Thrace forearc basin reflects the active influence of the uplifted accretionary prism. Deep-marine sediments predominate the basin fill that eventually shoals upwards into shallow-marine sediments. This trend is related to tectonically driven uplift and compression. Field, stratigraphic, sedimentological, petrographic, geochemical, and provenance data on the lower Oligocene shallow-marine deposits revealed the accretionary prism (i.e. Pindic Cordillera or Biga Peninsula) as the major contributor of sediments into the forearc region. Field investigations in these shallow-marine deposits revealed the occurrence of conglomerates with: (1) mafic and ultramafic igneous rock clasts, (2) low-grade metamorphic rock fragments, and (3) sedimentary rocks. The absence of felsic volcanic fragments rules out influence of a felsic source rock. Geochemical analysis indicates that the studied rocks were accumulated in an active tectonic setting with a sediment source of mainly mafic composition, and palaeodispersal analysis revealed a NE-NNE palaeocurrent trend, towards the Rhodopian magmatic arc. Thus, these combined provenance results make the accretionary prism the most suitable candidate for the detritus forming these shallow-marine deposits.

On the Position of the Obermittweida Conglomerate

On the south-west side of the little valley of the Mittweida, within an easy drive from Annaberg, about 25 miles south of Chemnitz, and twice that distance south-west of Dresden, there is a remarkable section which seems to show a strong conglomerate, crushed, it is true, but otherwise not much altered, intercalated among the gneiss and mica-schist which cover so large an area in that part of Saxony. It is therefore of some importance to inquire how far it would be possible to admit other explanations of the section than that which seems at first sight to be the obvious inference, and to consider whether an examination of the rocks in the field and a comparison of the mode of occurrence of other similar conglomerates render it possible to explain away the apparent interstratification of the conglomerate and gneissie series. I am indebted to Professor Credner, not only for much information on the subject, but for references to previous writers. The first notice seems to be that of Dr. Sauer, of Leipzig*, under whose guidance I visited this locality a few years ago, and whom I take this opportunity of thanking for much kind attention. The occurrence of this conglomerate is indicated on the Geological Map of Saxony and in the section given in its margin†. Professor Justus Roth, of Berlin, wrote a paper † upon these conglomerates in 1883, and afterwards referred to them in his work on General and Chemical Geology ∮ published in Berlin in 1887. Von