Interaction of magma and wet, unconsolidated sediments: a case study from Ilindenski Kamak, Chelopech Formation, Central Srednogorie

The Ilindenski Kamak is situated along the Ilindenska river valley, northwest of Chelopech village, and is composed of different types of volcanic and volcaniclastic rocks, which are interbedded by sandstones and mudstones, all of Late Cretaceous age. The architecture of the pile of extrusive andesitic rocks is interpreted as a subaqueous cryptodome or sill. The presented research deals with a variety of volcanic facies: 1, coherent andesitic domain; 2, quench fragmented domain (closely packed peperites); 3, globular peperites developed at the contact of wet, unconsolidated sediments.

Paleocene-Eocene volcanic segmentation of the Norwegian-Greenland seaway reorganized high-latitude ocean circulation

The paleoenvironmental and paleogeographic development of the Norwegian–Greenland seaway remains poorly understood, despite its importance for the oceanographic and climatic conditions of the Paleocene–Eocene greenhouse world. Here we present analyses of the sedimentological and paleontological characteristics of Paleocene–Eocene deposits (between 63 and 47 million years old) in northeast Greenland, and investigate key unconformities and volcanic facies observed through seismic reflection imaging in offshore basins. We identify Paleocene–Eocene uplift that culminated in widespread regression, volcanism, and subaerial exposure during the Ypresian. We reconstruct the paleogeography of the northeast Atlantic–Arctic region and propose that this uplift led to fragmentation of the Norwegian–Greenland seaway during this period. We suggest that the seaway became severely restricted between about 56 and 53 million years ago, effectively isolating the Arctic from the Atlantic ocean during the Paleocene–Eocene thermal maximum and the early Eocene.

Resistivity Data Modeling for Subsurface Volcanostratigraphy Construction of Cibadak Sub-Watershed, Bogor, West Java, Indonesia.

In Mt. Salak, there are six volcanic facies divided by eruption time seen from geomorphology data analysis and to identified the subsurface layer DC Resistivity method is applied. Beside resistivity, geostatistical parameters also influence the result model interpretation, so for obtain best model correlation parameters such as tilting, surfacing, variogram, grid method, and logarithmic distribution is applied. Using 18 points of acquisition data subsurface model is produce and then section model made to describe vertical resistivity distribution then correlated with facies lithology model. Based on that, produce three facies resistivity type namely: 0 – 100 Ohm.m (Low Resistivity Value) Interpreted as pyroclastic material composed as tuff and breccia that lies under lava. 100 – 300 Ohm.m (Medium Resistivity Value) Interpreted as breccia lithology type. Harder that pyroclastic material due to by this product is avalanches of lava. And >300 Ohm.m (High Resistivity Value) Interpreted as lava lithology that lies at high elevation and the hardest lithology in this area. From the model, pyroclastic layer that is modeled found at low elevation and based on the direction it described as oldest facies layer, but at the bottom of this layer lies high resistivity value that unknown product. It can be Mt. Pangrango product due to at low elevation predicted as combine area product from product of Mt. Salak and Pangrango. High resistivity value show lava lithology and lava facies located in high elevation and medium resistivity describe breccia lithology as avalanche product of lava (youngest pyroclastic facies) and found at 500 – 100 meters msl.

The volcano sedimentary sequence in the Upper Awash valley (Ethiopia): a type case of volcanoclastic sedimentation in a peripheral rift environment

<p>The Upper Awash valley runs across a volcano-sedimentary sequence dated from Late Miocene to about 500 my ago. The volcano sedimentary sequence in the Upper Awash valley developed within a closed basin at the western margin of the Main Ethiopian Rift branch and was affected by tephra sedimentation from nearby sources but also from volcanoes from the rift floor, and local fissural/dome eruptions. Dynamic interaction between rift tectonics, volcanic activity, tephra erosion and redeposition created a complex sedimentary environment constituting an exceptional fossil trap. In the area of Melka Kunture, the sediments host numerous fossils and archeological remains of Early-Middle Pleistocene (Oldowan and Acheulean) and Upper Pleistocene age. This is one of the most relevant African locations for researching human evolution.</p><p>The valley sequence formed after deposition of the large ignimbrite sheet of the Munesa tuff, within a paleo fluvial system which developed within lateral rift faults. Sedimentation rates significantly decreased after 500 my ago, probably due to decline of the volcanic activity in the area.</p><p>The basin stratigraphy consists of a composite sequence of primary (fall and flow) volcanic facies interbedded with reworked sediments emplaced in a low energy floodplain environment. The sequence is dominated by the deposit of one large pyroclastic density current (Kella Tuff) which is a main marker layer dated at 1.2 My. Deposition of the Kella Tuff had deep impact on the area leading to a complete reorganization of the drainage system and river channel migration and development of a disconformity in the southern Melka Kunture area.</p><p>Stratigraphic correlation is based on the interpretation of the basin history and evolution and has a crucial relevance not only for the reconstruction of the paleoenvironment but also for the interpretation of the paleontological and archeological data.</p><p> </p>

Groundwater Recharge Area Based on Hydrochemical and Environmental Isotopes Analysis in the South Bandung Volcanic Area

The determination of recharge areas needs to support the groundwater conservation in the southern volcanic Bandung area. This study aims to determine the recharge area based on environmental isotopes and hydrochemical. A sampling of 26 groundwater was carried out at springs, dug wells, and drilling wells. The variation in groundwater chemistry principally is controlled by a combination of ion exchange, silicate weathering, calcite, and dolomite dissolution of minerals. The hydrochemical facies were CaCl, CaMgCl, CaMgHCO3, CaHCO3, and NaKHCO3. The CaHCO3 facies describe moderate groundwater flows. The NaKHCO3 facies shows the mixing of shallow and deep groundwater. The recharge area in the central, proximal, and medial facies zone consists of 3 groups. Group I is considered water originating from local rainwater infiltration; Group II is considered the infiltration elevation which ranges from 980–1230 m asl; Group III estimated to be derived from the recharge elevation between 750–970 m asl, Group IV are more likely to show symptoms of evaporation or interaction with surface water. The discharge area is characterized by less active groundwater circulation, with dominant HCO3– and TDS value in the distal facies zone. Hydrochemical variation helped the identification of recharge areas in the volcanic facies.

An investigation approach of the volcanic geomorphology in the Călimani – Gurghiu – Harghita volcanic chain, Romania

<p><span><span>In poorly-exposed forest-covered volcanic areas, the main challenge in classical geological and geomorphological studies is the interpretations of landforms and volcanic structures. The usage of 3D models provides modern opportunities in visualization of volcanic landforms in volcanological studies in areas with dense vegetation cover</span></span><span><span>. </span></span></p><p><span><span>Geological mapping of the Neogene Călimani-Gurghiu-Harghita (CGH) volcanic chain is challenging due poor exposure of area. The Călimani-Gurghiu-Harghita volcanic chain exhibits ~10 My age range spanning from North (> 10 Ma) to South (< 0.03 Ma) linked to the evolution of the adjacent intra-mountain sedimentary basins (</span></span><span>Bilbor, Borsec, Gheorgheni, Upper Ciuc, Lower Ciuc, Brașov </span><span><span>and </span></span><span>Baraolt </span><span><span>basins</span></span><span>)</span><span><span>. The geomorphological analysis of the CGH volcanic chain is currently performed using SRTM data. However, the SRTM data are affected by the vegetation cover. Instead, we used a digital elevation models (DEM) built from topographic maps in combinations with volcanological field observations.</span></span></p><p><span>Our method uses a DEM 3D spatial view with overlay standard geological maps, shaded relief complemented with terrain analysis and landform recognition. Then, the study integrates field-based observations and geomorphological mapping results in a new general overview of the complex volcanic topography of the CGH volcanic chain. </span></p><p><span><span>Using </span></span><span><span>digital</span></span><span><span> elevation models (DEM) allows the general identification of volcanic facies distribution (proximal, medial and distal) belonging to </span></span><span><span>an individual</span></span><span><span> volcanic structures as well as the regional assemblages of the whole volcanic chain. DEM studies also permit to reconstruct the erosion level of volcanic edifices in conjunctions with field-based volcanological studies. This approach may also help identifying volcanological formations and various types of volcanic facies resulting from both construction and destructions of the edifices in poorly exposed areas.</span></span></p><p><span><span>By using this methodology a broad range of volcanic morphological features have been observed along the CGH volcanic range including the </span></span><span>Călimani</span><span><span> caldera morphology, features of the old and young debris avalanche deposits of various volcanic edifices and the youngest lava-dome morphology of </span></span><span>Ciomadul</span><span><span> volcano. Our DEM approach provides better results than those obtained by previous studies pointing out, for instance, that the volcanic edifices are highly to moderately eroded in the north and progressively better preserved toward the south. </span></span></p><p><span>Acknowledgements. The research was funded through CNCS – UEFISCDI, project number PN-III-P4-ID-PCCF-2016-4-0014, within PNCDI III.</span></p>

Extentional Fault Pada Daerah Compressive Tectonic Zone Sebagai Batas Cekungan Di Jawa Tengah Selatan

The extensional structure as a normal fault could be found in many places at the southern part of Java compressive tectonic regime. The research area is in the eastern part of the South Serayu Mountains. This normal fault structure is the boundary of the South Serayu Mountains at the eastern part with Kulon Progo Tertiary volcanic Mountains. In the field, these normal fault lineament zones create the Bogowonto river as a boundary of two different geological styles. The influence of this structure on the geological dynamic of the South Serayu Mountains and the Kulon Progo Mountains is important to be explained. The study was conducted by measuring and analyzing fault data and lithology that developed in the area around the two basins boundary. The distribution of the Kulon Progo volcanic rocks indicates the presence of the extensional fault structure. The volcanic facies distribution of the volcano is cut and becomes narrow in the west, while the northward is very wide. Normal fault striations analysis on the fault plane along the fault line shows the least stress trending west-northwest that has worked to create North-South normal faults. The fault-controlled by stress with the vertical main compression area. They have worked to create North Northeast-South Southwest (NNE-SSW) normal faults with westward dipping.