Tectonic evolution in the early to Middle Pleistocene off the east coast of the Boso Peninsula, Japan

The Kanto Basin developed, starting c. 3 Ma, influenced by the subduction of the Philippine Sea plate and the Pacific plate. Sediments in this basin have influenced the geomorphology of the Kanto region. In the Boso Peninsula, located at the eastern edge of the Kanto Basin, uplift continues in what is called the Kashima–Boso uplift zone. Although the development of this uplift after the Late Pleistocene is well understood, there are few data from the Early to Middle Pleistocene. In this study, we investigated the offshore shelf area east of the Boso Peninsula using a high-resolution seismic reflection survey, and report new information on the geological structure and uplift processes in the area from the Early to Middle Pleistocene. We identified the Kujukuri-oki anticline and the Kujukuri-oki normal fault zone. The Kujukuri-oki anticline, more than 47 km long, is north–south striking and deforms the Kujukuri-oki Group. There are numerous normal faults with displacements of less than tens of metres spread widely in the survey area (Kujukuri-oki normal fault zone). These findings reveal that the Kujukuri-oki anticline uplifted during the end of the Early Pleistocene and attenuated during the Middle Pleistocene. This anticline comprised the axis of the Kashima–Boso uplift zone at the Boso Peninsula from the Early to Middle Pleistocene and the Boso Peninsula is located at the western limb of this anticline.

Structure features and oil and gas prospect of paleochannel revealed with 2D seismic data in The East of Karakulsko-Smushkovskaya uplift zone

В настоящее время для многих недропользователей юга России представляют интерес нефтегазоперспективные объекты неглубокого залегания в виду небольших по- тенциальных затрат на их освоение. Данная работа посвящена изучению подобного объекта, связанного с перспективами выявления неантиклинальных ловушек углеводородного сырья. Цель исследования. В ходе сейсморазведочных работ 2008‑2019 гг. на территории Каралатского лицензионного участка (Астраханская область, восток Каракульско-Смушковской зоны поднятий) по сейсмическим данным был выявлен уникальный по размерам и форме для данного района исследования палеорусловой объект, приуроченный к эрозионному врезу по кровле верхнемеловых отложений. Основным направлением ис- следования являлось изучение его строения, природы и перспектив освоения. Методы исследования. Изучение объекта проводилось на основе имеющихся данных сейсморазведки (метод общей глубинной точки, двумерная модификация). Выполнена обработка и интерпретация накопленного сейсмического материала, сделан расширенный анализ скоростей, проведены структурные построения. Проведено ис- следование динамики волновой картины на качественном уровне и путём атрибутного анализа. Получен- ные результаты. Палеорусло формировалось, предположительно, в неогене, в условиях наклона терри- тории с севера на юг. В ходе его изучения было уточнено строение, конфигурация, предварительно оце- нены особенности залегания слагающих пород. Протяжённость объекта по оси – 25,4 км, площадь – 65,4 кв. км, глубина – 750‑1050 м. Точную стратиграфическую принадлежность выполняющих врез осадков ещё предстоит уточнить в виду отсутствия соответствующих данных глубокого бурения на территории исследования. Результаты привязки к скважинам сопредельного Кирикилинского участка указывают, что вмещающие породы относятся к верхнему мелу, на отдельных участках врез достигает и нижнемеловых осадков. Изучение аналогичных объектов и история геологического развития района позволяют предпо- ложить, что выполняющие врез породы относятся к плиоцену. Исследования указывают на то, что объект приурочен к главному руслу древней дельты или нижнему течению реки, аналогичной современной р. Волга. Энергия волн, отраженных от горизонтов заполняющих пород, выше, чем от горизонтов вмеща- ющих, что нехарактерно для известных палеорусловых объектов сопредельных территорий. При ско- ростном анализе волнового поля отмечены аномально низкие значения эффективных скоростей в зоне объекта. В результате получено подтверждение палеорусловой природы объекта, установлено сложное и непостоянное залегание пород с признаками латеральной смены литологического состава, возможного наличия флюидов. Полученные данные позволили предварительно оценить перспективы нефтегазонос- ности палеоканала и наметить планы дальнейшего изучения геофизическими методами, а также поста- новки поискового бурения Today carbohydrates blocks holders in south of Russiatake an interest inoil and gas potential objects with superficial bedding because of its reasonableexplorationcosts. This research work is devoted to study of so object concerned with carbohydrates traps revelation prospective. Aim. The unique because of its size and shape paleo-channel object confinedwith erosive cut on the top of cretaceous sediments was discovered with seismic data as the result of seismic prospecting works in 2008‑2019 on the Karalatskiy block (Astrakhan region, East of Karakulsko-Smushkovskaya uplift zone). The main direction of the research was the studying of its structure, origin and exploration prospective. Methods. The study was based on available seismic data (common reflection point method, 2D modification). Processing and interpretation of total seismic data volume were realized, expanded velocity analysis was performed, structure mapping were carried out. The qualitative leveldynamic analysis and attribute analysiswere realized. Results. It is supposed that ancient riverbed were forming in Neogene in condition ofinclination of territory in south direction. The structure and configuration of this object were defined more precisely and bedding peculiarities were preliminary estimated during studying. The extension of the object is 25.4 kilometers, the area is 65,4 square kilometers, the depth is from 750 to 1050 meters. Exact stratigraphy of sediments filling up the cut, needs to be defined more exactly because of lackof boring data on the field. The results of matching with wells of neighbor Kirikilinskiy block show late cretaceous age of base rocks, some spans of the cut reach lower cretaceous sediments. The study of similar objects and geological history of the region allow supposingthat rocks filling up the cut belong to Pliocene. Research shows that the object isconfined to mainchannel of ancient delta or lowerpart of ancient river similar to present-day Volga River. Filling up rocks horizons reflected waves energyis higher than for base rocks, this occurrenceis not typical for paleo-channel objects of contiguous areas. Abnormally low values of RMS velocities were detectedduring the velocity analysisin the object area. The confirmation of paleo-river genesis of the object was achieved as the result, complex andinconstant structure of the rocks with lateral lithology changing andpotential presence of fluids was detected. The result data allowed to estimate preliminary perspectives of oil and gas content for the paleochannel and to outline the subsequent geophysical study and exploration drilling performance.

Electrical signature of CO2-rich mineral groundwater systems - Application in the Ardennes, South-East of Belgium

<p>CO<sub>2</sub>-rich mineral groundwaters have been exploited for centuries for both bottling and thermal activities. The detection and understanding of productive areas is therefore of great interest to manage future supply in a sustainable way. CO<sub>2</sub>-rich mineral water systems are complex since they usually involve an intricated network of water bearing fractures enabling the uplift of CO<sub>2</sub>-rich groundwater to the surface, a process that is still poorly understood. Geophysical prospection is crucial to detect potential uplift zones and to address corresponding uncertainties before drilling operations.</p><p>In this context, non - to minimally - invasive near-surface geophysical methods can prove to be efficient. The objective of this contribution is to assess the ability of the induced polarization method, combined with the electrical resistivity technique, to make the distinction between CO<sub>2</sub>-rich groundwater from non-gaseous groundwater.</p><p>Several combined electrical resistivity and induced polarization tomography profiles were performed in the Ardennes (Belgium) where thousands of CO<sub>2</sub>-rich groundwater springs are observed. The profiles were all set immediately above known uplift zones. Inversion results were consistent between all profiles and important contrasts in both electrical resistivity and chargeability distributions in the vicinity of the uplift zone were observed, which were also reflected in the normalized chargeability sections computed on the basis of the measured data.</p><p>Low resistivity vertical contrasts extending in depth were observed and interpreted as saturated fractures enabling the uplift of deep groundwater to the surface. In addition, high chargeability anomalies appeared directly close to the CO<sub>2</sub>-rich groundwater resurgence. Those anomalies are thought to be associated to the presence of metallic oxides and hydroxides, as a result of dissolved metallic species precipitation in the upper part of the fractured aquifer due to the pressure decrease and change in redox conditions in up-flowing groundwater towards the land surface.</p><p>We conclude that the combined interpretation of electrical resistivity and induced polarization datasets is a very promising method for a more robust prospection of naturally sparkling groundwater.</p>