Lime mud was isolated from calcareous sands in the lagoonal basin of Manza Beach, the Okinawa Island. The lagoonal basin is enriched by both mud content and carbonate content towards the center, indicating that lime mud is enriched in the central portion of the low-energy lagoonal basin. Observation by the scanning electron microscopy (SEM) on the lime mud shows that it is composed by detrital, authigenic (precipitated), and cement crystals. Aragonite needles, as fragments of Halimeda, were occasionally observed to be present in the lime mud. Some spheres of radiating crystals were formed due to pore-water diagenetic processes. Lime mud deposited in the low-energy lagoonal basin may be an important material, which consolidates into limestone and which help to build up coral reefs.

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The motion of a density current in a rectangular channel can be described by coupled equations. The model includes the effect of slope, resistance exerted on a head of a density current and deposition of suspended sediments. Assuming that the volume of the head is h², the equations are reduced to simple forms with less parameters than previous models. Solutions show the downcurrent evolution of velocity of density current heads. The model is useful to quantify the behavior of natural large turbidity currents in a submarine channel.

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To make clear the initiation mechanism of oscillation ripples, detailed bedform profile was measured in a rotary-type water tank. As a result, small ripple (rolling-grain ripple) was formed in an incipient stage of the ripple development under various condition. Initiation from sparsely scattered sand particles on a rigid plane was observed in plane view in for further examination of the very early stage of the rolling-grain ripple. Although the condition in the tank are different from those in nature, it is very effective to demonstrate the initiation processes of oscillation ripples. The results are summarized as follows; (a) Immediately after the water oscillation start, sand clusters were arranged in line at right angles to the flow direction. Such a cluster is considered to be an initiation stage of the rolling-grain ripples. (b) The average cluster spacing is about 15-30 times of the particle diameter, and is generally independent to the orbital diameter. (c) In case of do/D less than 100, which approaches to orbital ripple condition, cluster spacing is more dependent on the orbital diameter. (d) Cluster spacing increases as increasing maximum flow velocity. On the basis of these observations, it is suggested that the cluster may be the basic cause of the initiation of ripples under oscillatory and probably unidirectional flows.

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The seasonal succession of coccolith in the Okinawa Trough was investigated through a time series sediment trap experiment from March 1993 to February 1994, and compared with coccolith thanatocoenoses in the underlying surface sediments. The coccolith flux was low in the shallow trap (water depth 600m) and markedly high in the middle (water depth 800m) and deep (water depth 1020m) traps. Coccolith assemblages of the three traps were similar to each other, except that the assemblages of the shallow trap differed from those of the middle trap during summer. On the other hand, the coccolith species composition of surface sediments shows considerable differences among the inner-middle shelf, shelf edge and the Okinawa Trough areas. These observation, together with comparison of coccolith species composition between trap and surface sediments, indicate the lateral transport of particulate matters from adjacent shelf edge and shelf slope of the Okinawa Trough to the central area of the Okinawa Trough.

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The Middle-Upper Pleistocene Shibikawa and Katanishi Formations exposed at the Anden Coast, Oga Peninsula, Akita Prefecture consist of shallow marine and nonmarine sediments. Authors divided these sediments into eight sedimentary facies based on their grain size, sedimentary structure and fossil assemblage, and postulated depositional environments and depths of these facies. Temporal variations of depositional depth are reconstructed at the Anden Coast according to successional change of facies along the exposure, and they are compared with the standard oxygen isotope curve by using widespread marker tephra layers as age control datums. Consequently, six sedimentary cycles caused by glacio-eustatic sea-level changes are recognized in the Middle to Upper Pleistocene deposits at the Anden Coast. The correlation between depth change and standard oxygen isotope curve allows more detailed estimation of the age for each sedimentary cycles. Based on the cyclostratigraphy, the stratigraphic divisions and boundaries at the Anden Coast must be re-defined.

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Flux of bedwaves was measured beside the wave-length, cross section, “reduced height” and migration rate during transition from plane bed through “upper ripples” to dunes, after decrease of flow velocity from upper-plane-bed regime. The flux has the minimum value on the way, while migration rate almost monotonously decreases, and length, cross section and “reduced height” show roughly monotonous increases even in the constant flow velocity. The reason flux has the minimum value may be explained by the abrupt decrease of migration rate in the early time and successive increase in “reduced height” in the later time, although this explanation does not include the influence of increasing bed roughness. The existence of the minimum may be related to the annexation of a few small bedwaves into a large one, which causes discontinuous bedform-transition. The possibility of explanation of this phenomenon by the change of dynamical characteristics of the fluid and/or moving sand in the whole systems can be pointed out now.
This paper is showing the importance of attention to the a mounts such as flux of bedwaves which would take the lead in understanding bedform dynamically, although details wait for further researches.

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Acid-resistant, organic-walled microfossils, or palynomorphs, are common in most fine-grained sediments since early Paleozoic. They can be extremely useful in solving geological problems both biostratigraphically and paleoenvironmentally. This article provides a review on two major groups of palynomorphs, dinoflagellate cysts and pollen/spores, and their application to sedimentary environmental analyses. Palynofacies is also discussed.

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