Terrace Deposits Research Articles

Holocene erosion and deposition within a small catchment of the northeastern Borisoglebsk Upland (Central European Russia)

During the Holocene, interfluvial landscapes of European plains have experienced alternating periods of relative stability and significant shifts in climate, soil and geomorphological development. Assumed to be an arena of major transformation their evolutionary model is not entirely resolved yet. Based on lithostratigraphic, geomorphologic and soil survey, new results on the Holocene dynamics of fluvial and related processes including landscape stabilization phases for one of the gully catchments draining the Borisoglebsk Upland northeastern slope towards the Nero Lake are presented. Common absence of the early Holocene deposits can be explained by generally negative sediment budget of the catchment. Nevertheless, continuous erosion was not likely whether rare climatic extremes probably were the case. A series of middle Holocene dates obtained by analyzing total organic carbon from organic-accumulative layers of buried soils, lake gyttja and peats highlights strong evidence of the synchronous phase of landscape stabilization in both upper and lower parts of the Puzhbol catchment accompanied by active infilling of small erosion cuts in its middle part. The upper part of the Puzhbol Gully fan sediment shows clear evidence of synchronous accumulation of agrogenic colluvium and gully alluvium since XIIth Century on top of the lake terrace deposits.

Geomorphological Analysis Applied to the Evolution of the Quaternary Landscape of the Tormes River (Salamanca, Spain)

This paper presents a geomorphological analysis of the Tormes River during the Quaternary. The Tormes River formed in the center-west of the Iberian Peninsula in the province of Salamanca. It runs along a Cenozoic basin with basement materials and through Varisco, and consists of mainly granitic and metamorphic materials, leaving a wide stream of river terraces, both erosional and depositional, that confirm its evolution throughout the Quaternary. Geomorphological analyses using Geographic Information Systems tools, Digital terrain model high resolution (MDT05, LIDAR), Orthophotos (scale 1:5000), and geological maps (1:50,000 Series Magna) have allowed different morphologies and depositional terraces to be distinguished, namely, 19 levels of erosional terraces and 3 levels of erosion surfaces. Based on these correlations, the levels of terraces in the Tormes River between T1 (+140 m) and T7 (+75–80 m) are located in the Pleistocene, those between T8 (+58–64 m) and T14 (+18–23 m) in the Middle Pleistocene, those between T15 (+12–13 m) and T17 (+6–7 m) in the Upper Pleistocene, and those between T18 (+3 m) and T19 (+1.5 m) in the Holocene. The erosion surfaces are divided into six levels: S6 (+145 m), S5 (+150 m), S4 (+160 m), S3 (+170 m), S2 (+180 m) and S1 (+190 m) located in the Lower Pleistocene, This work performs a geomorphological mapping procedure applied to the evolutionary analysis of the landscape, so that it determines different geomorphological units allowing the relief and morphology of the terrain in past times, establishing a dynamic analysis of the landscapes.

"Природні ритми формування Смотрицького каньйону за даними палінологічного аналізу відкладів низьких терас і заплави середнього Дністра"

"Природні ритми формування Смотрицького каньйону за даними палінологічного аналізу відкладів низьких терас і заплави середнього Дністра"

Late Pleistocene alluvial fan evolution along the coastal Atacama Desert (N Chile)

Due to their sensitivity to both tectonic activity and climatic variations, coastal alluvial fans (CAF) along the western flank of the Coastal Cordillera in the Atacama Desert (northern Chile) are important geo-archives for unravelling Quaternary environmental change. Our study focuses on terrestrial and marine deposits of five CAF complexes between 20° and 25°S along the coastal zone of the Atacama to identify phases of alluvial fan activity during the Late Quaternary. Based on a combination of luminescence dating and 10Be cosmogenic nuclide exposure dating as well as existing chronological data in the area, insights into climatic variations along the hyper-arid coast are presented for the Late Pleistocene derived from CAF morphodynamics. Activity of alluvial fans could be documented during time spans 95–80 ka, 60–45 ka, 35–20 ka, as well as the Holocene. Numerical dating of marine terrace deposits gives insights into the tectonic uplift of the Coastal Plain in northern Chile during the Late Quaternary period, for which estimated uplift rates between ~0.06 and ~0.57 m/ka were derived. While tectonic activity induces base-level changes, long-term tectonic activity rather indirectly controls alluvial fan activity. We suggest that alluvial fan activity is mainly controlled by atmospheric changes from the Pacific Ocean. Based on our observations, CAF in the hyper-arid Atacama Desert serve as suitable geo-archives for reconstructing climate changes during the Quaternary. In particular, the usefulness of alluvial fan systems in a water-limited environment is important for understanding the palaeoenvironmental evolution in a coastal desert.

Electron spin resonance dating of the culminant allostratigraphic unit of the Mondego and Lower Tejo Cenozoic basins (W Iberia), which predates fluvial incision into the basin-fill sediments

Abstract The Cenozoic basins of western Iberia have a culminant allostratigraphic unit (designated UBS13), which records the beginning of Atlantic drainage and predates the fluvial incision that led to the development of the present drainage networks. However, the available numerical dating is quite limited and mainly restricted to the lower-level terrace deposits. Therefore, this study uses for the first time the electron spin resonance (ESR) method to date this culminant unit in the Mondego and Lower Tejo Cenozoic basins of Portugal. The depositional age of this unit is supposed to lie between ~3.7 Ma (basal deposits) and ~1.8 Ma (uppermost deposits). The Al-centre provided reliable ESR data, but the dates obtained by using the Ti Li centre clearly underestimate the burial ages. With reference to the existing independent dating of the Vale Farpado site (3.7–3.6 Ma) at the lowermost basal level of the UBS13 deposits, the ESR (Al-centre) ages of 3.0 to 2.3 Ma obtained for the UBS13 basal and middle deposits give reliable estimates of the burial age. The ESR ages (Al-centre) obtained for the UBS13 uppermost deposits indicate a probable age of ~1.8 Ma. Thus, these results are of international significance, in that they constitutes the first numerical ages obtained for the uppermost levels of the Cenozoic basin-fills of western Iberia, which predate the fluvial incision that took place in response to lower Quaternary base levels.

Large-scale urban underground hydro-thermal modelling – A case study of the Royal Borough of Kensington and Chelsea, London

The shallow subsurface of dense cities is increasingly exploited for various purposes due to the significant rise in urban populations. Past research has shown that underground activities have a significant impact on local subsurface temperatures. However, the resulting spatial variability of ground temperature elevations on a city-scale is not well understood due to the lack of sufficient information and modelling complexity at such large scales. Resilient and sustainable planning of underground developments and geothermal exploitation in the short and long-term necessitate more detailed, more reliable knowledge of subsurface thermal status. This paper investigates the impact of some common underground heat sources such as train tunnels and residential basements on subsurface temperature elevation on a large scale and highlights the influence of local geology, hydrogeology, density, and type and arrangement of the heat sources on ground thermal disturbance. To tackle the size issues and computational expenses of such a large-scale problem, a semi-3D hydro-thermal numerical approach is presented to capture the combined influence of underground built environment characteristics coupled with ground properties on ground temperature elevation within the Royals Borough of Kensington and Chelsea (RBKC), London. Numerical results show that the extent of ground thermal disturbance is mostly affected by geological and hydrogeological characteristics in permeable ground (River Terrace Deposits). Density and spatial distribution of heat sources, however, are critical parameters in ground temperature evaluation in highly impermeable ground such as London Clay Formation. The locality of temperature rise and potential ground energy within immediate impermeable ground surrounding heat sources versus significantly large extent of ground thermal disturbance in permeable ground, highlights the significant dependency of ground thermal state and geothermal potential at the studied site to the ground and underground built environment characteristics and necessitates a better understanding of shallow subsurface thermal state for a sustainable and resilient urban underground development.

Pleistocene Coastal Evolution in the Makran Subduction Zone

Along the coast of the Makran subduction zone (SE Iran and SW Pakistan), active uplift combined with efficient erosion and vigorous sediment transport have led to marine terraces with unique morphology and sedimentology. These terraces are characterized by the systematic presence of an extensive 1–10Cm thick sandstone layer capping their wave-cut base. Our investigation of thirty-six sedimentary logs of the terrace deposits revealed a general prograding trend from nearshore to beach deposits moving upsection. The presence of a thick marine sedimentary succession above the erosive platform suggests continued creation of accommodation space following carving of the platform by wave-erosion (i.e., erosion of the platform occurred before the peak of the highstand). Deposition of prograding beaches above the platform is interpreted to have occurred during the sea-level stillstand and the start of sea-level fall and was favored by a high sedimentary supply. While some terraces evolve into a classic staircase morphology, others are found as flat-topped platforms bounded by steep cliffs, isolated within the low-lying coastal plain. We find that this morphological difference results from a contrast in bedrock erodability (resistant sandstone versus soft marl, respectively). The flat-topped isolated marine terraces with marl bedrock share morphological and sedimentological similarities with Holocene crenulated beaches currently developing in low-lying bays between headlands. As indurated beaches are uplifted into headlands, they influence the development of following generations of beaches before being eroded by surficial erosion and wave action. Our study shows that the coastal geomorphology of the Makran coast is dictated by the interaction between tectonics (providing relative sea-level fall and juxtaposing units of different erodability at the same structural level by faulting), differential erosion between hard and soft rock (responsible for the presence of isolated headlands) and coastal sedimentary transport processes (permitting accumulation of extensive beach deposits).

Supercritical flows overspilling from bypass‐dominated submarine channels and the development of overbank bedforms

AbstractOverbank deposits of submarine channels are typically thin‐bedded, fine‐grained and predominantly characterized by a series of sedimentary structures interpreted to record a relatively simple history of waning flow. Here, a new type of bedform indicative of Froude‐supercritical flow is reported from successions of thin‐bedded turbidites interpreted as channel overbank deposits in the Upper Cretaceous Rosario Formation, Baja California, Mexico. A link is demonstrated between the development of overbank deposits in the form of depositional terraces or internal levees and contemporaneously active sediment transport, bypass and deposition of coarser‐grained material in a channel. The overbank bedforms overlie an erosion surface and contain a suite of sedimentary structures indicative of initially Froude‐supercritical flow conditions and a progressive waning of flow strength. In some cases, a stacked repetition of facies is interpreted to record a rejuvenation of flow energy. The characteristic sedimentary sequence observed is as follows: (a) long wavelength, low amplitude erosional surface with superimposed scours; (b) antidune backsets; (c) upper stage plane‐parallel lamination; (d) subcritical climbing ripples; (e) supercritical climbing ripples; (f) lower stage planar laminated tops; (g) a sharp upper surface. The exact vertical sequence of sedimentary structures encountered varies depending on the point of observation with respect to the bedform crest and distance from the parent channel. The recognition of these distinctive bedforms allows for interpretation of sediment bypass and proximity to a channel thalweg. These bedforms have not hitherto been described and provide a further example of the range of flow processes operating in submarine channel–levee systems, which aids depositional environment interpretation in both subsurface and outcrop studies.

Weibull 함수를 이용한 입도 분리와 하안단구 퇴적층의 기원

Weibull 함수를 이용한 입도 분리와 하안단구 퇴적층의 기원

Record of environmental changes and fluvial phases in the Late Holocene within the area of Podhale (the Carpathians, southern Poland): studies in the Falsztyński valley

The Falsztynski valley, in the eastern part of Podhale, Poland includes a low terrace spanning the stream channel, the structure of which has been studied in nine profiles. Five gravel levels and five mud levels with plant and abundant mollusc remains are described, temporally constrained by ten radiocarbon dates. The terrace deposits represent the terminal part of the Atlantic Phase and all of the Late Holocene. The mollusc analysis helped identify phases of environmental change, notably one in the Middle Ages connected with intensive settlement activities in the area of Podhale. These include deforestation, affecting mollusc communities with replacement of forest assemblages by open-country species. The gravel levels records increased fluvial activity periods correlated with humid climate phases. It is possible to distinguish five such periods corresponding to the transition of the Atlantic and Subboreal phases, the middle part of the Subboreal Phase, the transition of the Subboreal and Subatlantic phases, the younger part of the Subatlantic Phase, and the last 200 years. These correspond to the periods of increased fluvial activity in the valleys of other Carpathian rivers.

Analyses of Retrogressive Slope Failures in Terrace Deposits

Abstract Slope failures in terrace deposits were explored and studied in this research. In situ exploration and sampling were carried out in Shin-Shan Village of Nantou County after a typhoon. Large direct shear tests in the laboratory were performed to measure the shear strength of the material. The soil-water characteristic curve of the soil was derived from pressure plate tests. The cross-sectional profiles of the failed slope before and after the typhoon in this area were obtained using a digital elevation model and 3-D terrestrial scanner, respectively. The numerical software SEEP/W and SLOPE/W were used to analyze the slope stability under similar rainfall to the typhoon. Different groundwater levels and river water levels were considered to compare the factor of safety values and reveal the failure processes of the slope. The possible failure of the slope may be due to scouring of the slope toe by fluvial erosion caused by rising water river levels, mud flows, or both, based on the investigated profiles and numerical simulations. The estimated length of scouring was about 20 m long. Based on the numerical modeling, the possible mechanism of failure for this length of scouring could be due to multiple retrogressive failures after toe scouring.

Neoformations (Nodules and Placic Layers) in Surface-Gleyed Loamy Sandy Soils of the Northern Part of the Tambov Plain

In the middle part of the profiles of light gray soils (non-gleyed, deeply gleyed, weakly and strongly gleyed) on silty loamy sandy two-layered deposits of the river terraces in the Tambov Plain, placic layers are formed. Nodules are confined to the arable layer, if surface water stagnation occurs. Angular black nodules of less than 2 mm in size with a high Mn content are specific for weakly gleyed soils, grayish brown nodules of 7–10 mm in size are common in strongly gleyed soils. The Cd and Pb accumulation coefficients in the nodules reach 100–300, those for Co and Mo are 10–100; for Zn and Cu, 2–5; the content of P2O5 is 1.0–1.5%, the content of organic matter in the nodules is 1.8–2.5%, and it has a fulvic nature (Cha/Cfa < 0.4). The placic layer density reaches 1.6 g/cm3, and the aeration porosity is reduced to 3–6%. They are highly acidic, 1.5 to 3 times higher in the contents of clay, Al, Fe, Mn, and trace elements than the enclosing material. A reliable quantitative criterion for the evaluation of the agroecological status of light gray surface-gley soils can be the Fe/Mn ratio in 1 N sulfuric acid extract from the nodules (bogging factor according to Zaidelman and Ogleznev).

Evaluating Quaternary activity versus inactivity on faults and folds using geomorphological mapping and trenching: Seismic hazard implications

The incorporation of active faults in seismic hazard analyses may have a significant impact on the feasibility, design and cost of major engineering projects (e.g., nuclear facilities, dams), especially when located in the site vicinity. The regulatory definition of active versus inactive fault is generally based on whether the fault has ruptured or not after a specific chronological bound (i.e. fault recency). This work presents a methodology, mainly based on geomorphological mapping and trenching, for determining whether specific faults can be considered as active or inactive. The approach is illustrated through the analysis of several faults located in the Spanish Pyrenees (Loiti, Leyre, La Trinidad, Ruesta faults). The 29 km long Loiti Thrust was included in the Neotectonic Map of Spain as a probable neotectonic structure. Previous works, based on geomorphological investigations, incorporated the 28 km long Leyre Thrust as a significant seismic source in a probabilistic seismic hazard analysis, which challenged the seismic design of nearby large dams. The production of detailed geomorphological strip maps along the faults allowed the recognition of specific sites where the faults are covered by Quaternary deposits. The establishment of chronosequences (pediments-terrace sequences) and the available geochronological data helped identifying the most adequate morpho-stratigraphic units for satisfactorily evaluating fault activity vs. inactivity. The excavation of trenches at the selected sites provided unambiguous information on the presence or lack of deformation in the Quaternary cover overlying the fault, and the origin of scarps (tectonic versus erosional). Trenches were also useful for collecting samples and reliably measuring the relative height of terraces overlain by thick colluvium. The evidence gathered by these methods were complemented with the numerical dating of non-deformed slope deposits covering a fault, the analysis of the longitudinal profiles of old pediment surfaces located in the proximity of a fault, the examination of a cave situated next to a fault searching for speleoseismological evidence, and regional geodetic and seismotectonic data (GPS measurements, earthquake focal mechanisms). The integration of all the data, and especially the trenches dug in non-deformed old terrace deposits (>100 ka) truncating the faults, indicates that the analysed faults can be considered inactive and that previous neotectonic postulations were based on non-valid geomorphological interpretations.

Accurate determination of the Pleistocene uplift rate of the NE Japan forearc from the buried MIS 5e marine terrace shoreline angle

We used tephra and phytolith stratigraphy to refine Pleistocene marine terrace chronology, with reference to reported eustatic sea levels associated with the dated marine terraces, and estimated uplift rates along the northern part of the northeast (NE) Japan forearc (the overriding plate in the northeast Japan subduction zone) by using elevation measurements of the buried shoreline angle beneath well-dated marine terrace surfaces to derive more accurate paleo-sea levels. On the Kamikita Plain, northernmost Honshu Island, the T4 and T3 marine terraces were correlated to marine isotope stage (MIS) 5e and MIS 7c or 7e, respectively, by the stratigraphic positions of the tephras Toya (MIS 5d) and WP (MIS 7b). The T2 terrace surface, which had previously been assigned to MIS 7, is buried by loess correlated to MIS 8 by its phytolith assemblage; therefore, this terrace can be reasonably re-correlated to MIS 9. The reported optically stimulated luminescence ages for Middle Pleistocene terrace deposits tend to be younger than these refined terrace ages. We used the buried shoreline angle elevation, determined from the reconstructed profile of the marine terrace deposits and paleo-sea cliff, to refine the uplift rate of T4 since MIS 5e. The accurate rate thus determined, 0.18–0.26 m/ky, is slower than the rates initially inferred from the inner edge of T4, but faster than the reported rate (0.14–0.19 m/ky, as recalculated here) inferred from the assumed MIS 5e shoreline elevation. In addition, it is roughly compatible with the rate inferred by using the top of T2 lagoon deposits to determine the shoreline elevation during MIS 9. Therefore, during the last 300 ka, the uplift rate of the Kamikita Plain has been constant at about 0.2 m/ky. This Pleistocene uplift is probably attributable to a combination of moment release on the megathrust, isostatic uplift driven by crustal thickening, and reverse faulting of the upper crust.

Quaternary regional evolution based on karst cave geomorphology in Picos de Europa (Atlantic Margin of the Iberian Peninsula)

Alpine caves have attracted considerable geomorphological, paleoenvironmental and hydrogeological interest since climate, glaciations, relief uplift, fluvial incision and karst aquifer control their evolution. In the Atlantic Margin of the Iberian Peninsula, Picos de Europa mountains is among of the most important karst areas of the World containing some of the deepest caves explored today. In addition, these mountains represent a reference site for the study of the Last Glacial Cycle in the SW of Europe. This work aims to reconstruct the Pliocene-Quaternary evolution of this region based on geomorphological and geochronological research (U/Th and Al/Be) carried out in four alpine caves. Cave geomorphological mapping evidences that 12 km of studied caves are made up of 47% vadose canyons and shafts, 45% phreatic/epiphreatic conduits organised in six cave levels, and 7% breakdown-modified passages. Their deposits are characterized by speleothems, including flowstones, that represent ancient cave pavements, fluvial terrace deposits with allochthonous clasts, slackwater deposits related to cave floods, and debris deposits produced by breakdown. One 26Al/10Be burial age indicates a minimum age of 2.1 ± 0.5 Ma for the caves origin, allowing estimation of the mountain uplift at 0.15–0.25 mm·a−1 since the Late Pliocene. Twenty-eight new 234U/230Th ages and another six previous speleothem ages give ages ranging from MIS 8 to 1. The speleogenetic model comprises six phases of regional evolution. Phase 1: main development of cave levels with SE-directed phreatic flow in the NW of Picos de Europa, in a karst partially or totally covered by the detrital Permian-Mesozoic cover, presently eroded. Phase 2: erosion of the Permian-Mesozoic cover and onset of vadose conditions before 260 ka, in a karst-affected by fluvial captures. Phase 3: cave infill during 220–145 ka, probably caused by the erosion of Stephanian detrital outcrops. Phase 4: erosion of cave infill during 125–45 ka. Phase 5: apparent pause in the speleothem formation during 45–25 ka related to dry and cold regional conditions. Phase 6: reactivation of the speleothem precipitation since 25 ka. Regional climate, fluvial incision and the ancient presence of detrital outcrops at the surface appear to have been the main factors that controlled the cave evolution and regional geomorphological evolution throughout Pliocene and Quaternary times.

하안단구 퇴적층의 지구화학적 특성과 기원지 - 단양천, 금천 유역을 대상으로 -

하안단구 퇴적층의 지구화학적 특성과 기원지 - 단양천, 금천 유역을 대상으로 -

Microblade remains from the Xishahe site, North China and their implications for the origin of microblade technology in Northeast Asia

Here, we discuss the earliest microblade sites in China and the development of microblade technology in greater Northeast Asia. The Xishahe site was discovered in Huliu River terrace deposits in the Nihewan Basin, North China. Chronometric dating indicates the site was first occupied ca. 29–28 ka cal BP, while the microblade remains date to about 27 ka cal BP. Xishahe has yielded some of the earliest radiocarbon dated microblade technology in China, and evidence suggests that its appearance and disappearance are positively correlated with climate change. The microblade technology identified at Xishahe is different from other, younger microblade sites in China, specifically those associated with the mature wedge-shaped core technique. Further, although the Xishahe microblade cores are well-shaped with platform preparation and could successfully produce parallel-sided flakes, the overall morphology of these cores was highly variable and lacked standardization. Obvious technological differences can be seen in microblade assemblages dating to periods before and after the Last Glacial Maximum (LGM; ca. 24–18 ka cal BP).

Tectonic and climatic controls on Quaternary fluvial processes and river terrace formation in a Mediterranean setting, the Göksu River, southern Turkey

AbstractClimate and tectonics effect the fluvial evolution of the Mediterranean Mut basin. The basin contains a river terrace staircase of 16 levels (T16–T1) ranging from 365 to 10 m above the current Göksu River in its middle and lower sections. These river terraces records tectonic uplift in the Mut basin. Optically stimulated luminescence (OSL) dating of the fluvial sediments of the youngest terrace (T16) provides a chronology for the assessment of the important impacts of climatic changes. The ages from the youngest river terrace deposits in T16 may be subdivided into two intervals: (1) 239–194.7 ka during the later part of Marine Oxygen Isotope Stage (MIS) 7, implying that the aggradation of T16 started in (the final phase of) this warm period; and (2) 187.9–171 ka during much of MIS 6. Thus, it appears that the Göksu River continued depositing sediment from an interglacial into a glacial time. The differences in climate-driven fluvial evolution between this Mediterranean fluvial system and the classical, well-studied temperate–periglacial river systems in Europe may be the result of different vegetation cover and greater thaw of more intense snowfalls.

Remnants of paleoflora in impact melt rocks of the El'gygytgyn crater (Chukotka, Russia)

AbstractRemnants of paleoflora were discovered in impact melt rocks from the El'gygytgyn crater, Chukotka, Russia. El'gygytgyn is a 3.58 Ma, 18 km diameter impact structure in Chukotka, northeastern Russia. A circular crater basin is surrounded by an uplifted rim. The crater floor is occupied by the El'gygytgyn Lake, 12 km in diameter, surrounded by lacustrine terraces up to 80 m in height. Impactites found at the El'gygytgyn crater include impact melt rocks, glass bombs, and shock metamorphosed volcanic rocks. Most impact melt rocks occur only in redeposited state in the terrace lake deposits. Floral remnants were discovered in impact melt rocks from various locations in the terrace deposits. The floral remnants include fragments of leaves, cell tissue, and undetermined organic matter that occur in vesicles within glassy melt rocks and impact melt breccias. After the discovery of floral remnants in impact melt breccias from upper Miocene strata in Argentina, and the description of floral imprints in the Dakhleh Glass of proposed impact origin in Egypt, the detection of paleoflora remnants in impact melt rocks of the El'gygytgyn structure is the first such occurrence in a confirmed impact crater on Earth.

РОССЫПИ ЖЕЛЕЗОСОДЕРЖАЩИХ МИНЕРАЛОВ В САХАЛИНСКОЙ ОБЛАСТИ

Ю.А. Билибин неоднократно подчеркивал, что для того, чтобы понять картину образования россыпей, необходимо учитывать полный цикл их превращений. Много внимания было уделено в последнее время проблемам поиска древних погребенных россыпей и россыпей сложного строения. Богатые резервы полезных ископаемых в россыпях объясняются множественностью их генетических типов, позволяющих вовлекать в промышленную эксплуатацию новые месторождения. Актуальность работы обусловлена необходимостью выявления новых источников получения железа, титана и ванадия в условиях сокращения ресурсов минерально-сырьевой базы. Поисковые работы, выполняемые с целью выявления россыпей, наиболее перспективных для разработки, могут проводиться на основании понимания генезиса их формирования. Цель работы: исследование закономерностей распространения россыпей железистых минералов в пределах Сахалинской области, выявление петрогенетических особенностей преобладающих минералов, определение перспектив освоения месторождений железосодержащего сырья, оценка экономической целесообразности его добычи. Методы. Исследованы железо-титан-оксидные минералы из различных по кремнекислотности горных пород островодужных вулканогенных комплексов Большой Курильской гряды. Для исследований были подготовлены шлифы горных пород, отобрана магнитная фракция из протолочек. Шлифы пород изучались под поляризационным микроскопом. Порошок протолочек горных пород и мономинеральных фракций исследовался посредством химических аналитических методов (гравиметрического, титрометрического, спектрофотометрического, рентгенофлуоресцентного, масс-спектрометрического с индуктивно-связанной плазмой). Результаты. Исследованы закономерности формировании железистых россыпей и определены их основные типы. На побережьях Дальнего Востока России встречаются два типа россыпей с различными условиями питания. Одна из них – Курило-Камчатская провинция собственно титаномагнетитовых россыпей – расположена на территории Сахалинской области. На островах Курильской дуги преобладают современные пляжевые россыпи и дюнные отложения низкой террасы. Главная роль в обеспечении минералами россыпей этого типа принадлежит туфопесчаникам, пемзам и пемзово-шлаковым пирокластическим толщам. Кристаллы железосодержащих минералов в горных породах вулканогенных комплексов имеют довольно разнообразные размеры: от мелких, пылеватых до крупных хорошо выраженных кристаллов, размерами более 1–2 мм. Химический состав титаномагнетитов различных вулканических комплексов изменяется в зависимости от кремнекислотности пород. Продуктивные породы характеризуются повышенным содержанием железа, титана и ванадия. Прибрежно-морские, а также древние погребенные россыпи содержат значительные объемы железосодержащих минералов. Изучение технологических схем переработки железосодержащего минерального сырья показало, что некоторые из них позволят провести его переработку с получением востребованных конечных продуктов. При определенных экономических условиях разработка россыпей может быть целесообразной.