Terrace Plains Research Articles

Geoconservation of Groundwater in the Getourism Area of Olele Village for the Development of the Tomini Bay Geopark

Geoconservation is an important effort in preserving geological diversity. Geoparks act as a link to encourage geoconservation. This research aims to evaluate the geology, geosite potential and groundwater availability in Olele Village, Gorontalo. This research aims to determine geological conditions, geosite potential, groundwater availability and groundwater conservation measures. The methods of literature survey, field survey, field data collection and ArcGis 10.8 data analysis were used. Stratigraphy shows the sequence of Reef Limestone (Ql), Pinogu Volcanic Rock (TQpv), Bone Diorite (Tmb), and Bilungala Volcanic Rock (Tmbv). Geomorphology includes reef terrace plains, alluvial plains, pyroclastic flow hills, and lava flows. Lithological contacts between reef limestone and pyroclastic breccia mark the Olele Geosite. Water quality is influenced by the level of rock passability and rainfall. Olele Village has good groundwater potential with a groundwater table depth of 1-8 meters. Groundwater conservation measures involve monitoring, public education, water use management, sustainable agriculture, wetland rehabilitation, development of alternative infrastructure, and mitigation of tourism impacts. Thus, this research emphasizes the need for sustainable strategies for the conservation of geological and groundwater resources in this area.

Origin and hydrochemical characteristics of groundwater in the Northeastern Patagonia, Argentina: the relationship with geomorphology and soils

In arid zones, geomorphology and soils play a fundamental role in groundwater surveys as they condition the recharge phenomenon and some processes that modify water chemistry. The objective of this work was to identify the groundwater provenance and the relationship between its chemistry and isotope contents with the geomorphology and soil in the northeastern Patagonia, Argentina. Over an area of 10,600 km2, groundwater levels and major ionic and stable isotopic contents were measured. The main geomorphological units were mapped using satellite images and digital elevation models. In soils, pedogenetic carbonate contents (PC) and clay accumulation index (CAI) were measured. Different hydrochemical facies were identified in relation to geomorphological units, being the Cl–SO4–Na and Cl–Na ionic types dominant in fluvial terrace plains (terrace associations, TAs). The Cl–SO4–Na types are the most saline groundwaters and are coincident with the TA where Petrocalcids are the dominant soils. With less salinity contents, Cl–SO4–Na and Cl–Na types are the groundwaters associated with TA where the dominant soils are Natrargids and Haplocalcids. The only sector with Cl–HCO3–Na is those with fresh water coincident with the Aeolian field unit, where Psamments soils develop. Likewise, groundwater is isotopically differentiated in response to the origin being mostly allocthonus in the fluvial terrace plains and from local recharge in the Aeolian fields. The fluvial terraces are gravel deposits that would favor a local recharge, but this is prevented both by pedogenic carbonate and clay contents which developed in the upper part of the deposit. In this way, the measurement of pedogenetic carbonates and clays becomes soil properties of utmost importance to be considered in groundwater prospecting in arid regions worldwide.

ГЕОМОРФОЛОГІЯ, НЕОТЕКТОНІКА ТА ПАЛЕОГЕОГРАФІЯ ТЕРИТОРІЇ ГЕОЛОГІЧНОЇ ПАМ'ЯТКИ "СТАРУНЯ"

A survey of geomorphological and neotectonic features around "The Starunia paleontological site" allows to produce a complete description of paleogeographic conditions and geological age of the Pleistocene mammals. The floodplain terraces I and II and a redevelopment valley have been distinguished on the geomorphological map and a sketch of cross-section of the Velyky Lukavets River valley. The location of fossil fauna (mammoth and rhinoceroses) has been indicated. The prospect of finding new extinct Pleistocene mammals preserved in bitumen and salt has been substantiated. In the late Pliocene, the northeast macro-slope of the Carpathians was dissected by many parallel river valleys transverse to the main Carpathian direction of structures and longitudinal valleys. The rivers took down coarse-grained material from the mountains that formed the high terraces and debris cones (inland delta) of the ancient Dniester valley. The latter was formed at the foot of the Carpathians, in the area of the modern village of Loyeva and the Dniester, then gradually retreated 30–40 km to the northeast and took its present location on the longitude of the town of Halych. Its block mass alluvium formed two ancient terrace plains – Krasna and Loyeva. The climate was subtropical, the type of the present Mediterranean, as evidenced by the red-brown color of the clayey cement of coarse-grained alluvium and cover clays with active migration of iron and manganese. In the early Pleistocene, in the wide swampy valley of the river Lukavets Velykyi, the winding beds of the last stage of river valleys development were quietly meandered. Monotonous dark gray to black marsh accumulations, silt clays, biogenic silts with numerous plant remains accumulated. Landscapes – tundra with dwarf birch, alder, willow etc. The climate was severe, consistent with Wurm (Valdai) glaciation (59–13 thousand years ago). Perhaps just then herds of mammoths and rhinos grazed in the valleys of the Starunia territory and our ancestors Cro-Magnons lived here. The extremely important practical value of Starunia is that further expansion of research and creation of an international ecological-tourist center – the Geopark of the Ice Age will significantly improve the socio-economic status of the village of Starunia, provide the population with new jobs and raise the level of tourism in the Ivano-Frankivsk region. The authors hope that the unique phenomenon of Starunia will be preserved for future generations.

Soil genesis on the raised coral reef terraces of Ishigaki- and Okinawa-islands in the Ryukyu islands, Japan

Soil forming processes on the raised coral reef terraces under humid sub-tropical maritime climate were investigated in Ishigaki- and Okinawa-islands in the Ryukyu Islands. Analyses of soil morphology and soil chemical properties showed that there is a close relationship between soil development and the relative age of the terrace plains, as follows: The soils develop from Coral Limestone Lithosols (Lithic Udorthents) on the lowest terraces, through Rendzina-like soils (Typic Rendolls) on the lower terraces, Terra fusca-Iike soils (Lithic Eutrochrepts) on the lower middle terraces, Mottled Terra fusca-like soils (Aqu-ollic Hapludalfs) on the higher middle terraces and finally to Terra rossa-like soils (Mollic Hapludalfs) on the limestone plateaux corresponding to the higher terraces. However, the status of free iron oxides in all these soils is similar to that of Red soils, reflecting the bio-climatic conditions of the humid sub-tropics. It appears therefore necessary to develop criteria that may enable t...

FORMATIVE AGE AND RATE OF DEFORMATION OF FLUVIAL TERRACES ALONG THE LOWER STREAM OF THE SHINANO RIVER, NORTHEAST JAPAN

Fluvial terraces are widely distributed along the lower stream of the Shinano River from Ojiya city to Nagaoka city, Niigata prefecture, northeast Japan. This area has experienced active crustal movement since the Tertiary period, and the deformations of terrace plains by active folds and faults are distinctly recognized. Therefore, this area is well known as one of the best fields in Japan for studies on active crustal movement, especially on active folds. Many works have been published about fluvial terraces and active crustal movement in this area since pioneer works by Ikebe (1942) and Otsuka (1942), but few detailed studies about formative age of fluvial terraces have been published except Ota (1969). Tephrochronological approach is usually effective for regional geologic chronology. The purposes of this paper are to determine the formative age of fluvial terraces by means of tephrochronological approach, and to calculate the deformation rate of terrace plains. Main results are summarized as follows. 1. Three dated marker tephra layers were found out in this area. They are Aira-Tn ash (AT, ca. 21, 000 22_??_000 y. B. P.), Daisen Kurayoshi pumice (DKP, ca. 45, 000_??_47, 000 y. B. P.), and Nakago pumice layer (NG, ca. 130, 000_??_150, 000 y. B. P.). 2. Based on the stratigraphic relationships between terraces and these marker tephra layers, formative ages of fluvial terraces were determined as follows; A Terrace (Koshijippara terrace): ca. 130, 000_??_150, 000 y. B. P., B Terrace (Kowadappara Terrace): ca. 50, 000_??_60, 000 y. B. P., C Terrace (Funaokayama Terrace): ca. 21, 000_??_25, 000 y. B. P., D_??_F Terraces: younger than 20, 000 y. B. P., perhaps Holocene. 3. The average rate of the northward tilting of the fluvial terraces in the region is recalculated as about 0.15_??_0.17mm/km•year during the past 130, 000_??_150, 000 years, and about 0.13_??_0.16mm/km•year during the past 50, 000_??_60, 000 years. Both values correspond well with the rate of the tilting deduced from the precise relevelings (0.19 or 0.15mm/km•year, Mizoue et at., 1980). 4. The average rates of the tilting at the west wing of the Ojiya syncline (Ikebe, 1940) during the past 130, 000_??_150, 000 years and 50, 000_??_60, 000 years are 0.4‰•1, 000 years and 0.4_??_0.5‰•1, 000 years, respectively. 5. The above-mentioned facts in 3 and 4 imply that the active folding in this area has proceeded at a nearly constant rate during at least the past 150, 000 years. 6. The Katakai faults (Ota, 1969) cutting A Terrace have displaced at the order of 0.01_??_0.1m/1, 000 years.

NOTES ON ACTIVE FOLDING IN THE LOWER REACHES OF THE SHINANO RIVER, CENTRAL JAPAN

The deformations of fluvial terraces along the lower course of the Shinano River and its tributaries are well. known examples of active folds in Japan. The Shinano River flows almost northward approximately parallel to the main synclinal structure of the Plio-Pleistocene Uonuma Group, and pours into the Sea of Japan. Therefore, active folds succeeding its structure appear as the deformation of cross sections of terrace plains. The pattern of deformation due to active folding is demonstrated in the terrace distribution map and cross sections. Details of several examples of folded terraces are explained based on the descriptions of newly found good outcrops which confirm the deformation of terrace surfaces concordant with the foldings of terrace deposits.

DISPLACEMENT OF FLUVIAL TERRACE PLAINS ALONG THE MIDDLE COURSE OF THE SHINANO RIVER, CENTRAL JAPAN

The middle course of the Shinano River is situated in the north-eastern part of Fossa Magna which is known as a Green Tuff region. This region has experienced active crustal movement since the Tertiary period. Along the middle course of the Shinano River, fluvial terraces are distributed. The geology of this region mainly consists of unconsolidated rocks, so-called the Uonuma Formation. This formation is composed of silts, sands and gravels, and is 2000m thick in maximum. The course of the Shinano River is one of the syncline of the Uonuma Formation which extends SST-NNE. Terrace plains of this region are classified into nine groups, by the geomorphological and tephrochronological methods. The writers tried to make clear the relation between the displacement of the terrace plains and the crustal movement presumed by the geological structures of the Tertiary formation, and to investigate the nature of the crustal movement after the formation of the terrace plains. Main results are as follows. 1) As for the terrace plains formed at the same stage, it is clear that the quantity of their displacement is proportional to the degree of dip of the Uonuma Formation. For example, the displacement of the first terrace along the right bank of the Kiyotsu River varies from 2 to 10 degrees proportionally to the increase of dip of the Uonuma Formation. In the place where the bed rocks are horizontal, no displacement of the terrace plains is observed. 2) In a same place, it is to be noted that the higher and older terrace plains show more amount of displacement than the lower. It is also noticeable that the terrace plains along the each tributary converge towards the course of the Shinano River. A close relationship was found between the mode of the crustal movement during the late Quaternary period estimated from the displacement of the terrace plains and the mode of the crustal movement since the Tertiary period, presumed from the geologic structures. It may be concluded that the mode of the crustal movement since the Tertiary period has continued till recently and the displacement of terrace plains show latter portion of the crustal movement.

Quaternary Volcanic Ashes in the Narugo and Onikobe Volcanic Areas

A. The Narugo volcanic areaThe original form of Kata-numa which seems as explosion crater is supposed to be a paleo-lake formed by the crustal deformation. The mudflow materials and volcanic ashes erupted out under the fluviatile-lake environments.The volcanic ashes from the Narugo volcanoes covered the mudflow materials and terrace plains except the present river bed. These ashes are classified into two main volcanic ashes depending upon the soil colors. One of them is the black volcanic ash, and the other is the brown volcanic ash. The soil color of the black volcanic ash is presumed to have been derived from the colored minerals and humus.B. The Onikobe volcanic areaThe original form of the Onikobe basin was formed by the crustal deformation, and deposited the lacustrine sediments in the paleo-lake. The first eruption of the volcanic ejecta occurred under the fluviatile-lake environments. The volcanic ashes from the Onikobe volcanoes accumulated on the outer mountains, inner volcanic bodies and terrace surfaces except the present river bed.However, the volcanic ashes in the Katayamajigoku and Arayu areas include the plant leaves. These ashes are supposed to have been deposited on the bottom of the paleo-lake in early Quaternary age. Under the polarized microscope, no mineral fragments are recognized in these ashes. This is a remarkable point of the characteristics compared with the volcanic ashes of the other areas investigated. This reason is supposed that the alteration of the volcanic ashes has been accelerated by the solfataric action and subterranean heat etc.

Geomorphological Development of the Area of Bělá nad Radbuzou

Geomorphological Development of the Area of Bělá nad Radbuzou

Study of Active Fold in Japan

History of active fold study in Japan is critically reviewed and current problems in this branch are discussed with introduction of a case study of active fold along the River Shinano. The term active fold is here used for a fold (structure), the last deformation of which occurred in a very recent period (less than 105 years B. P.).Active fold, as reported first by Otuka (1941, 1942a) and Ikebe (1942), was discovered by deformed river terraces and vertical displacement of bench marks, both of them being concordant to underlying Neogene fold structures. Significance of this discovery lies in that the tectogenic stress which yielded the fold structure is in action at present and that we can observe the time mode of deformation of the structure.During the period 1943-1959, besides accumulation of examples found in the inner belt of Northeast Japan, a direct approach was tried by Miyamura (1943, 1949, 1956) for obtaining data of vertical displacement by bench marks newly set up for this particular purpose (Fig. 1). In the course of his study, the Futatsui Earthquake (1955, M. 6.2) happened to occur near the newly set levelling route. This event associated with possible pre-seismic deformation and coseismic progress of active fold, much stimulated general interest in the relationship between active fold and seismic activity.Since 1960, still more examples have been added, partly due to impact of UMP and earthquake prediction project. Based upon the accumulated results, active folding has been discussed with related crustal movement such as crustal unduration and active faulting. The following conclusions seem to be almost established by the recent work.1. Active fold has been formed with the maximum time rate of folding (tilting) of the order of 10-6 per year during the past 104∼5 years. This rate is abnormally high compared with deformation in other continental parts of the globe.2. Time rate of deformation is generally inversely correlated with wave length. The above maximum rate is attained by the fold with wave length of several kilometers or less. This high-rate, short-wave fold is characteristic of areas with thick semiconsolidated sediments such as the inner belt of Northeast Japan. This fact suggests that folding of this sort is genetically related to the presence of thick soft material.3. Due to the high rate, displacement observed within ten years or less, is able to be correlated to tectogenic deformation.An active fold along the lower course of the River Shinano is described referring mainly to Ota (1969). The distribution of river terraces is shown in Fig. 3 along with a syncline and an anticline of terrace deformation. The axes of this active fold almost duplicate those of the fold in the underlying Plio-Pleistocene deposits. Exact correlation of terraces is a difficult but important problem in an area of high rate of deformation like this. Fig. 4 is a cross section of folded terraces. Fig. 5 presents the distribution of bench marks near Sekihara shown in Fig. 2 and its relation to fold axis of terrace plains. Fig. 6 shows a part of the bench mark net set up for the study of active fold, vertical displacement during the past nine years, and the distribution of the Geodimeter baseline. This area apparently experienced steady progress of folding with a rate of 10-6 during the past 70 years, without appreciable earthquakes.From the foregoing review and a case study, future problems as below were summarized and discussed:1. Further accumulation of reliable examples.2. Quantitative study of original form of terrace topography.3. Age determination of topographic plain.4. Nature and distribution of active fold and its dependence on the physical property of underlying rocks which is the historic result of geology of the area.5. Mechanism of active fold, its dependence on depth and measurement of horizontal strain.

GEOMORPHOLOGICAL STUDY OF PUMICEOUS TERRACE DEPOSITS ALONG THE RIVER YONESHIRO, NORTHEAST JAPAN

The River Yoneshiro rising from the southern part of the Towada Volcano flows westward through Hanawa, Odate and Takanosu Basins into Noshiro Plain, and it finally pours into Japan Sea at Noshiro City, Akita Prefecture. Terrace plains are well developed along the river course. The aim of this report is to make clear the subaqueous sedimentation of pumiceous fragments in the lower terrace deposits. First of all, the writer surveyed the distribution of the terrace plains and investigated their longitudial profil, micro-relief (figs. 1, 2, tab. 1). As to the result of these morphological observation, he presumed the distribution of the river agencies at the stage of the terrace plain formation. Then, he observed sedimentary facies of the terrace deposits, and classified them according to the lithologic kind and size of deposits (phot. 1_??_4) into such five types as pumiceous gravel layers (Ka-, Ge-facies), pumiceous sand layers (Od—), lithic sand layers (Ki—) and lithic gravel layers (Ot—) . And his survey was conducted to discusse the herizontal and vertical distrbution of each other (figs. 3, 4). So, it was worthy of his notice that pumiceous gravel layers (Ka-, Ge-) were always accumulated on pumiceouse sand layers, in reverse the case of lithic layers. Further, he measured the grain size, ratio of mixing of lithology, ratio of suspensive and floating material, bulk density and absorption of pumiceous gravels, and sheir sinking ratio (figs. 5, 6, tabs. 2, 3, 4). The results of these field survey and laboratory analysis, are summerized as follow: 1. Enumerating these facies in order of the presumed strengeth of the river agencies, they arrange Ot-, Ki-, Od-, Ge-and Ka-facies, so Ot-facies show the strongest of all.2. Pumiceous fragments are accumulated under the qualitive environments as compared with lithic fragments of same size.3. In spite of their small grain size, pumiceous sand leyers are formed under stronger river agencies than pumiceus gravel layers. Ka-facies layers are accumlated in the dum up basin, and Ge-facies layers are formed on the top of the natural levees or sand banks.

A Mechanism of Formaticn of Fluvial Terraces

Two examples of microtopography of fluvial terrace plains are described from the River Shinano, central Japan (Figs. 2 and 3). The topography consists of narrow, shallow depression beneath the backward scarp, and of low swells in front of the depression. They are regarded as abandoned channels and old meander-channel bars, respectively. Another example of the meander-channel bars, just growing into terraces with the similar topography is given (Fig. 4a and 4b).From the observation of these examples, a generalized mechanism of formation of a type of fluvial terraces are reduced (Fig. 5). Wider terraces will be formed from braided river floors which are considered to be aggregates of this kind of channel bars. They belong to non-cyclic erosional terraces which do not necessarily represent discontinuous uplift of the area.

COASTAL TERRACES OF THE SADO ISLAND, JAPAN

The Sado Island with 857 km2 in area is situated in the Japan Sea, about 35 km off Honshu. This islandd consists of two regions, Osado and Kosado. The former region which lies in the northern half is larger than the latter and also higher in altitude, and considered to be a tilted block with steeper foreslopes on the east side. This area is composed mainly of volcanic rocks such as andesite, liperite, basalt, and Miocen green tuff. Surrounding this island are coastal terraces developed widely. The author surveyed these coastal terraces and their deposits in the Osado region, in order to clarify their distribution, altitude, and nature and to consider the geomorphic history. The main results are summarized as follows: 1) The coastal terraces are divided into six plains owing to their altitude and continuity. They are as follows: the first terrace (160-220 m in altitude), second (80-140 m), third (60-120 m), fourth (35-70 m), fifth (25-40 m), and the sixth (5-8 m). 2) These terraces are well developed in the western coastal region in general. On the east side, however, they are no more than a fragmentary distribution. Among the terraces of the Osado region, the third and fourth terraces show a broad and cotinuous distribution. The sixth terrace is also developed all around the island in spite of the limited width. 3) Considering from the thickness and facies of the terrace deposits, the nature of the terrace plains can be classified into four groups. A a In the western coastal region, every terrace plain is of a marine origing formed by striking abrasion of the open sea. B: On the coast along the Mano Bay, the terraces are thought to be of a marine origin formed by the cut and built action of waves in the inland bay. C: In the Kuninaka Plain, the second and third terraces are elevated fans built by the rivers from the northern mountains. On the contrary, the fourth terrace is a dissected coastal plain which consists of thicker neritic sediments deposited in the inland bay. D: In the eastern coastal region, marine terraces are hardly recognized, and most of the flat plains are very small elevated fans consisting of poorly sorted boulders transported by the torrential streams down from the steep slopes. 4) The sixth terrace continues to the alluvial plain of the Kuninaka area, composed of marine alluvial deposits containing the fauna which indicates warmer water temperautre than the present sea in the vicinity and having about 70 m in thickness. Therefore, the formation of the sixth terrace plain is to be correlated with the transgression of early alluvial age which is recognized at many places in Japan. As for the fourth terrace which has a wide distribution and thicker neritic sediments, it may be considered that it was built by the transgression preceeding the regression of the last glacial age just before the alluvial trans-gression. 5) The differences in the character of terrace plains which were mentioned in 3) seem to haue been influenced chiefly by the asymmetry of topography and the condition whether open-sea-facing or not. Rock control is recognized where stacks are found on the terrace plains in the volcanic rock areas of Osado. Concerning the formation of the terrace as a whole, however, it is of the secondary importance, since topographic differences such as those of slopes seem to be the primary differentiating causes. 6) On every marine terrace plain, the elevations of the ancient strand lines increase in an accelerated manner towards the middle part of both sides of the Osado coasts, and this tendency is more evident on the older terraces. This means the upwarping movement with the axis at the middle part of the island has continued since the formation of the first terrace plain.

Quaternary Geology and Geomorphology of Sendai and its Environs (2)

Three problems are discussed in this paper, they are (1) the double flexured structure of the Aobayama and lower terrace plains; (2) the pollen analysis of the Pleistocene peat layers; (3) the heavy mineral composition of the Pleistocene volcanic ash layers.The Aobayama Plain which is a depositional surface of the Pleistocene Aobayama Formation underlying with unconformity the Medeshima Volcanic Ash (Fig. 2) is subdivided into four berms (Fig. 1). The boundaries between them run in NW-SE direction and parallel to the Kagitori Line which is an axis of flexure of the Tertiary system of the same area. The Aobayama Formation is flexured on these boundary lines as the superficial topograpyh. The berms of the Aobayama Plain are flexured by another axis with NE-SW trend. The second flexure has one syncline and two anticlines which grade into the thrust fault in the eastern part of the Aobayama Plain. The axes of the syncline and anticlines extend northeastwards into Sendai City where the lower terraced plains are gently undulated by the same axes.Pollen analysis have been made of five peat layers, which occur in different terrace deposits, in the environs of Sendai. The pollen floras of the peat of the Aobayama Formation and of the Upper Sendai Terrace deposits show that the forests were influenced by a temperate condition rather cooler than that of the Dainohara Terrace deposits (Fig. 3).Heavy mineral analysis have been made of four volcanic ashlayers. The heavy minerals of the Koeji and Medeshima Volcanic Ashes are mainly composed of magnetite and hornblende with abundant hypersthene and few augite and the Medeshima Volcanic Ash comprises zircon in addition to them. The Hirasawa Volcanic Ash is characterized and distinguished from the others by the proportion of augite. The heavy minerals of the Nagano Volcanic Ash are composed largely of magnetite and hypersthene (Fig. 4).

RIVER TERRACES AND EARTH MOVEMENT ALONG THE RIVER TOYO

The River Toyo flows into Atsumi Bay, taking the northeast-southwest direction along the median line which is one of the most important tectonic lines in Japan. There is a considerable difference in the topography and geology between the areas of the right side (Inner Zone) and the left (Outer Zone) of the river (Figs. 1 and 2). The authors surveyed the terrace topography and deposits along the River Tokyo in order to make clear the process of the formation of terrace plains and the earth movement in this region. The main results are as follows: 1) The terrace plains of this region are classified into three kinds: the upper, the middle and the lower. The upper terraces are distributed widely on the right side of the river and are correlated with the surface of Takashihara. The middle terraces are most remarkable and also widely distributed on the right side of the river. The lower terraces are subdivided into two. The lower terraces I distributed locally are intermediate terraces between the middle terraces and the lower terraces II which gradually change to the present flood plain (Figs. 3 and 4). In the both terraces, the upper and the middle, in the lower course from Shinshiro City their distribution and altitudes are different from those in the upper course area, and the gradients of the former terrace plains are steeper than those of the latter's (Tab.1). So the upper and the middle terrace plains situated in the lower course have the characteristics of fan-like topography. 2) The origins of the terrace deposits are classified into two groups (Tab. 2). The one is the terrace gravels which usually contain the liparite gravels derived from the uppermost area, and are transported by the River Toyo itself. The other is the fanglomerates which consist of the angular gravels of mica schist or mica gneiss constituting the Inner Zone mountain land, and seems to be transported by the small tributaries. The distribution of the fanglomerates coincides with that of the fan-like topography above mentioned (Figs. 5, 6 and 7). 3) Small faults cutting the bedrock are observed at the mountain foot of the Inner Zone (Fig. 5). Strikes of the fault plains are mostly NE-SW, namely, it resembles to the direction of the steep scarp and the arrangement of kernbuts and kerncols. Judging from the data mentioned above, the authors have reached tentative conclusions concerning the process of the formation of the terrace plains and the earth movement as follows: It seems that during the formation of the upper terrace plain the deposition of the River Toyo took place more actively than during the middle and lower terrace plain formation. The small tributaries from the Inner Zone mountain land also deposited the great amount of the fanglomerates following the deposition of the upper terrace gravels. It means that there was a tendency to elevate more rapidly in the Inner Zone than in the Outer Zone area. Such a tendency of the earth movement is also observed during the middle terrace plain formation, but the amount of this is smaller than the case of the upper. However, this tendency is not observed during the lower terrace plain formation. Moreover, even in the Inner Zone area, this tendency is clear at the lower course from Shinshiro City. The longitudinal profile of each terrace plain is astringed toward the lower course. Consequently, it is considered that the amount of the upheaval movement connected with the formation of the terrace scarp is greater in the upper course area than in the lower course in each stage. Such a tendency is contrary with that of the earth movement observed in the region in Tempakuhara which is older than the terrace plains in question.

SAND DUNES SITUATED ON THE MARINE TERRACES IN NISHI-TSUGARU REGION, AOMORI PREFECTURE

In Nishi-Tsugaru region along the coast of the Japan Sea, there develop typical marine terraces which are partly covered by sand dunes. The author surveyed the disribution, geomorphic features and composition of the sand dunes. The results are summarized as follows: 1) Sand dunes orerlie the A horizon of soil formed at the uppermost part of terrace gravel beds along the outer margins of the second terrace plains of which the altitude is about 50-60 m, the third terrace plains (30-40m) and the fourth terrace plains (5-10m) . The geomorphic features of the sand dunes situated on the older (higher) terraces are not so typical as those situated on the younger (lower) terraces, although on the first terrace, there is no sand dune. (Fig. 1 and Photos. 1-5). 2) The distribution of the sand dunes in this region is conditioned dy the exposure of the coast against the prevailing winds, and they are distributed on the coast of the direction from NE to SW facing winds from WNW in winter. (Fig. 1 and Tab. 1) 3) Moreover, the formation of the sand dunes is controlled by the amount of sand supply, which is conditioned by the nature of bed rock of the coast. In this region, the distribution of the sand dunes is limited to the area composed of Tertiary sedimentary rocks which are easily decomposed into a large amount of sands. But, in the coast to the south cf Fukaura, is composed of volcanic rocks which are more resistant to weathering than the former, neither beach nor sand dune can be formed. (Fig. 1) 4) The sand dunes are usually composed of well sorted medium or fine sands (smaller, than 1 mm in diameter), and the grain size of the older sand dunes is somewhat smaller than that of the younger ones (Tab. 2). It seems to be a result of subaerial weathering after the formation of the sand dunes. Because such a thendency corresponds to modificatin of the geomorphic features of the sand dunes. 5) The sand dunes modify the terrace topography. They give the terrace plains small reliefs. The terrace scraps facing the prevailing wind of winter are covered by sands, and their slopes are very gentle. On the other hand, the terrace scarps free from sand dunes preserve their original steep slopes (Tab. 3).

SIZE DISTRIBUTION OF CEMENTING MATTER IN THE TERRACE GRAVELS AT CHICHIBU BASIN

At the Chichibu Pasln in Kanto District, the writer researched the size distribution of cementing matter in the fluvial terrace gravels. The results of mechanical analysis are shown in Figs. 1, 2, and Table 1. The tendency of river development indicated by the size distribution and. the sorting of cementing matter has some resemblance to that presumed by the field observation of facies of each terrace deposit, which was reported in the previous paper. It is probable that the results of such mechanical, analysis play be able to. shoe. the difference of river development and the environment, of deposition between the River Ara and Akahira at each stage of the formation of terrace plains.

GEOMORPHOLOGY OF THE REGION AT THE UPPER COURSE OF THE RIVER WATARASE

The River Watarase is well known as a flood river in Japan, which causes great damages to the human life every year. The writers have studied on the geomorphology and geology in the upper region of the River Watarase, especially on valley forms, stream terraces, kinds of rocks and rock structures. Main subjects which are explained in this paper are summerized as follows: (1) The region at the upper course of the River Watarase is chiefly composed of Chichibu system (paleozoic rocks), granites, quartz-porphiries, diabases and other rocks. Landforms of this region are remarkably controlled by the distribution of these rocks and structures. (2) The writers have observed many fault plains in detail along the stream course of the Watarase, surveying dips and strikes of the fault plains, breccia, fault clay and shatter zones. It is concluded that many of the stream courses of Watarase and its tributaries are determined by the fault lines. Ages of those faults are old and many valleys of this region are faultline valleys. However, the writers have discovered an example of a new fault moved again after the building of terrace plains. In the region of Chichibu system, many trikes of faults are NNE-SSW or NE-SW and dips are almost vertical or high degree resembling the tendency of bedding plains of rocks, while in the region of granite, the strikes of the faults are generally NW-SE and the dips are of low degree. (3) The narrow stream terraces along the River Watarase are classified into three groups. Terrace plains are well developed in some local small basins formed at the cross points of fault lines. At the region of granite, Which forms a clear knick point of the river profile, terrace plains are not well developed, but many small cones are seen, formed by little tributaries from the mountain sides.

River Terraces in Chichibu Basin

Chichibu Basin is situated at the north-eastern part of Kanto-Mts. In this basin river terraces are distributed along the River Ara and River Akahira. We have researched the terrace deposits, especially size and angularity, sorting of terrace gavels, altitude and thickness of gravel beds, from which we have studied on the environment of deposition and the process of formation of terrace plains. The main subjects are summarized as follows: (1) Terrace plains in this basin are classified into. three groups. (2) Upper terrace gravels which form a divide between two rivers are fanglomerates of the River Ara and the upper terrace plain is a remnant of dissected fan. (3) Middle and lower terrace gravels which are found a long two rivers are deposits of old flood plains. (4) The thickest gravel deposit on each terrace is found at the southern part of Chichibu City, and it suggests relative subsidence of this region during each stage of terrace building, related to the earth movement of this basin.

Geomorphology of the Region at the Middle Course of the River Watarase, With Special Reference to the Distribution of Gravels

At the region of the middle course of the River Watarase, gravel beds are classified as follows: (1) Godo Gravel Bed (oldest gravels) Their angularity and composition show that they are not the deposits of the River Watarase. (2) Upper terraces and the initial surface of Omama Fan They were formed before the deposition of Kanto Loam. (3) Lower terraces and the erosion surface Omama Fan It seems that they were formed during the deposition of Kanto Loam. (4) Flood plains of the River Watarase The writer researched the ratio of composition of gravel samples on each of terrace plains, from which he tried to interpret the mechanism of. formation of terrace plains. In this region the writer chose 22 stations for sampling. Samples were taken by roughly outlining a small area of about one meter in diameter. From this area 100 gravels were chosen at, random. Fig. 4 and Table 1 show the composition of the grayel samples collected. In Godo Gravel Bed, Pal ozoic rocks and Tertiary tuffs are common, white andesites only 11%. So the deposition of such gravels have not much relation to Akag. Volcano. Gravel beds on the initial surface of Omama Fan and upper terraces of Shiobara and Kambal, however, are mainly composed of andesites involved about 80%, which were chiefly derived from Akagi Volcano. It seems that those plains were formed by the increase of materials from Akagi Volcano, and the deposition of volcanic detritus from Akagi was most active during the formation of those upper terraces. On the lower terrace plains and the erosion surface of Omama Fan, percentages of andesites in gravel samples show 50_??_60% and that of the flood plains about 30%. Therefore, the writer's conclusion is that the deposition, of materials from Akagi Volcano decreased during the formation of lower terraces and such tendency of decrease has continued up to the present.