Form, facies, and depositional history of the North Long John rock avalanche, Owens Valley, California

Sedimentology of gravelly Lake Lahontan highstand shoreline deposits, Churchill Butte, Nevada, USA

Recent bottom sediments from the neighbourhood of Alexandris, Egypt: el Wakeel Saad K., 1964. Mar. Geol., 2 ( [formula omitted]): 137–146.

Le parcours maritime des eaux du Congo : Donguy Jean-René, Jean Hardiville and Jean-Claude le Guen, 1965. Cah. Oceanogr., CCOEC., 17 (2): 85–97.

Genesis and depositional model of subaqueous sediment gravity-flow deposits in a lacustrine rift basin as exemplified by the Eocene Shahejie Formation in the Jiyang Depression, Eastern China

A conceptual model for block-and-ash flow basal avalanche transport and deposition, based on deposit architecture of 1998 and 1994 Merapi flows

We discuss the implications of a set of terrestrial cosmogenic nuclide (TCN) ages on blocky, cross-valley deposits of large rock avalanches along upper Indus streams. The dated deposits are key to understanding late Quaternary events that play a major role in landscape evolution in the Karakoram Himalaya. The landslides occurred between 3 and 8 ka ago, challenging existing chronologies of events along Indus streams. The TCN ages may support a mid-Holocene climatic role in preparing slopes for failure, but the balance of evidence suggests that large earthquakes triggered the landslides. Each landslide dammed the Indus or a major tributary and controlled base level and sedimentation for millennia. They produced landforms long regarded as characteristic of the region, including extensive lacustrine deposits, flights of river terraces, epigenetic gorges, and sediment fans. Until the 1990s, most of the landslides were interpreted as moraines; related lacustrine and other sediments continue to be attributed to glacial damming, and stream terraces to tectonic processes. Generally they were seen to originate tens of thousands to hundreds of thousands of years earlier than the new ages require. Instead we argue that they record interactions among different geomorphic processes in landslide-fragmented valleys during the Holocene. Rather than being geomorphic markers of tectonic and climatic events, the landslides have buffered or redirected climatic and tectonic forcing. In such an active orogen, millennia-long episodes of zero net bedrock incision at each site are surprising. However, rates of sedimentation above landslide barriers and erosion controlled by their breaching are close to today9s high measured rates for geomorphic activity. We propose that landslide-fragmented rivers may, in fact, characterize interglaciations and future patterns of upper Indus landscape evolution at time scales of 10 3 to 10 4 years.

A gravitational spreading origin for the Socompa debris avalanche

The Aguero fanglomerate body developed in late Oligocene to early Miocene time at the northern margin of the Ebro Basin where the emergent southern Pyrenean thrust front created a topographic high. Tectonic activity in the thrust belt strongly influenced the sequences and structures within the fan deposits. The fan deposits display an initial coarsening-up sequence. Intraformational unconformities subdivide the proximal sediments into a series of wedges. These result from a continued uplift along the thrust front during the initial stages of fan development. A major intraformational unconformity marks the top of this sequence and the start of a fining-up sequence. Further tectonic activity in the thrust front is indicated by a syn-depositional synclinal fold which decreases in amplitude up sequence. Rejuvenation of fan sedimentation to form a second coarsening-up sequence reflects renewed activity in the thrust front. This second sedimentation event resulted in a plus 200 m thickness of massive conglomerates. The geographical limits of fan sedimentation can be determined because the fan deposits are lithologically distinct from the other Ebro Basin molasse in the area. The area of the drainage basin of the fan can also be estimated by consideration of the clast types present in the fan deposits. The fan and drainage basin areas are estimated to be 6 km2 and 10 km2 respectively.

The Northeastern United States was probably glaciated several times. In most valleys, however, the last ice sheet eroded down to bedrock, and all of the stratified drift that now overlies bedrock can be ascribed to the last deglaciation. Only in northeastern Ohio, northwestern Pennsylvania, and parts of southwestern and central New York do valleys commonly contain complex stratigraphy that results from repeated glaciation: multiple till sheets interlayered with lacustrine silt and with sand or gravel aquifers. Most stratified drift was deposited in the major valleys or lowlands when they were inundated by rising sea level or, more commonly, by proglacial lakes. Coarse-grained sediment was deposited in these water bodies as deltas and subaquatic fans, commonly amid stagnant ice blocks near the margin of the active ice, and also in channels within the ice sheet. The sediment was derived partly from debris-laden basal ice and subglacial till, entrained by meltwater flowing through tunnels, and partly from fluvial erosion of recently deposited drift in the uplands that bordered the valley-bottom lakes. The stratified drift consists of three facies deposited successively: proximal coarse-grained heterogeneous ice-contact deposits, followed by distal fine-grained lake-bottom sediment, and finally by coarse-grained surficial sediment deposited in shallow lakes or stream channels. One or two facies may be absent at any given site, but all three can be identified in many places along every major valley or lowland. Coarse-grained ice-contact deposits commonly constitute the bulk of the stratified drift in narrow or shallow valleys, whereas in broad lowlands they are widely scattered and occupy only a small fraction of the valley floor. In valleys where depth to bedrock exceeds about 100 feet, the bulk of the stratified drift commonly is fine grained, and transmissivity is not generally proportional to saturated thickness. Coarse sand and gravel tend to be more abundant in the southern part of the glaciated Northeast than farther north. Several concepts or generalizations are widely applicable in interpreting the distribution of coarse-grained aquifers within glacial drift in the glaciated Northeast. In many localities, stratified drift can be divided into a series of morphosequences, which represent successive time intervals during deglaciation. Grain size decreases distally within each morphosequence; coarse, heterogeneous ice-contact sand and gravel predominates at the proximal end, whereas coarse sand commonly overlies lake-bottom fines at the distal end. Successive morphosequences can be difficult to distinguish, however, and coarse proximal deposits that are especially prominent and easily recognized commonly overlie relatively high bedrock and have small saturated thickness. Some investigators have inferred that water-yielding coarse sand and gravel are widely distributed at the base of the stratified drift, overlying till or bedrock, as a result of continuous deposition of subaquatic fans at the ice margin during retreat, even in broad lowlands where surficial stratified drift is predominantly fine grained. Other studies indicate, however, that subaquatic fans did not form in all valley reaches and that within broad lowlands they are restricted to relatively narrow zones that follow former subglacial channels.

Clinical data suggest a relationship between in vivo deposition patterns of cigarette smoke particles and the occurrence of tumors in the lung. Traditional dosimetry models fail to predict the preferential proximal deposition of cigarette smoke in the human airways, which resembles deposition of aerosol with a larger mass median aerodynamic diameter (MMAD) than that representative of cigarette smoke. Previous work has shown that accounting for the so-called cloud effect leads to enhanced proximal deposition and to better agreement with clinical and experimental data. This work presents an improved model of transport and deposition of cigarette smoke in the airways of smokers, accounting for possible particle-particle interactions (cloud effect) and their effect on the mobility of individual particles and on the deposition profile. Brinkman's effective medium approach is used for modeling the flow through and around the cloud, with the cloud's permeability changing according to the cloud's solid volume fra...

The Nangodani Valley is part of the caldera floor at the southern foot of Nakadake, a post-caldera volcano of Aso Volcano, SW Japan. In this valley, lava flows from the Nakadake and Takadake volcanoes are widely distributed. However, their exact distribution was not known because they were covered by fan deposits and mantle-betting tephra layers. In this study, we used various topographic maps and aerial photographs provided by the Geospatial Information Authority of Japan (GSI). Although outcrops of the lava itself are scarce, we have succeeded in estimating the distribution of lava flows by carefully observing the topography, especially the flow paths of rivers. The marginal cliffs of lavas are not easily eroded and the natural flow paths from the volcanic slopes are blocked. In fact, we found outcrops of lava were outside the previous distribution area of the lava. This fact indicates that the lava is likely to be distributed in a wider area than the previously indicated distribution area. As for the outflow area of the lava, it was confirmed from the microscope observation that the lava flowed at the point which was not considered as the outflow area of Takadake lava. The distribution of the Nakadake old-edifice lava is partly hidden by the Takadake lava, which flows around it to the vicinity of the Takamori lava. Therefore, the Nakadake and Takadake lava flowed almost at the same time, but the Takadake lava is considered to have flowed slightly after the Nakadake. There are many natural springs in Nangodani Valley, which is consistent with the distribution of the lava revealed in this study.

Conglomerate reservoirs in alluvial fans commonly contain economic crude oil, but it is challenging to depict the distribution of conglomerate reservoirs or to summarise the sedimentary model in alluvial fans deposits owing to their complex lithofacies changes and variable hydrodynamic conditions. This paper focuses on the Poplar River alluvial fan in the northwest Junggar Basin, China, as a special case to analyse its sedimentary processes and to build a sedimentary model through detailed outcrop mapping and grainsize analysis. The Poplar River alluvial fan is a braided river-dominated fan with the characteristics of a large fan size (approximate 327.6 km2), gentle slope (∼<0.04–0.07°), coarse sediments (mainly cobbles or finer pebbles) and rare fine-mud sediments deposited from floods. In this alluvial fan, 15 lithofacies are identified that mainly formed in five hydrodynamic environments: (i) debris-flow deposits; (ii) high-flow traction current deposits; (iii) low-flow traction current deposits; (iv) still-water deposits; and (v) eolian deposits. Moreover, the sedimentary processes on the Poplar River alluvial fan can be divided into flood and interflood periods. During flood periods, sediment deposition plays a major role on the alluvial fan. From the proximal to distal parts, six lithofacies associations can be identified: feeder-channel and sheet-flow deposits in the proximal part, sheet flood and braided-stream deposits in the intermediate part, and channel deposits and wetland deposits in the distal fan areas. During the interflood periods, sediment reworking is the most important function, and three lithofacies associations are identified: main-channel deposits in the proximal fan, braided-trench deposits in the intermediate fan and wetland deposits in the distal area. The braided-stream deposits, braided-trench deposits and sheet-flood deposits have the best potential for high-quality aquifers or oil reservoirs based on their moderately well-sorted grains and high primary permeable intervals. KEY POINTS Fifteen lithofacies and eight lithofacies associations are identified in the Poplar River braided river-dominated alluvial fan. The aggradation process of the studied alluvial fan can be divided into flood and interflood periods. The flood-period braided-fluvial deposits, interflood main-channel and braided-trench channel deposits are the facies with best reservoir potential.

We propose that a “local first” approach should be applied to the interpretation of provenance indicators in glacigenic sediments of all depositional ages, especially where the glacier flow path is poorly constrained and the records of potential source lithologies are incomplete. Provenance proxies, specifically U-Pb detrital zircon geochronology, of glacigenic sediments are commonly used to infer the size and distribution of past ice centers, which are in turn used to inform ancient climate reconstructions. Interpretations of these proxies often assume that similar provenance signals between glacigenic units of the same depositional age are evidence that they were deposited by the same glacier, even when those units are, not infrequently, separated by thousands of kilometers. Though glaciers are capable of transporting sediment great distances, this assumption is problematic as it does not acknowledge observations from the geologic records of Pleistocene ice sheets that show provenance proxies in glacial sediments are most likely to reflect proximal (within 100 km) sediment sources located along a specific flow path. In a “local first” approach, provenance indicators are first compared to local source lithologies. If the indicator cannot be attributed to proximal sources, only then should progressively more distal sources be investigated. Applying a local first approach to sediment provenance in ancient glacial systems may result in significant revisions to paleo ice sheet reconstructions. The effectiveness of the local first approach is demonstrated here by comparing new U-Pb detrital zircon dates from the Permo-Carboniferous glacigenic Wynyard Fm with progressively distal source lithologies along the glacier’s inferred flow path. The Wynyard Fm and source lithologies were compared using an inverse Monte-Carlo unmixing model (DZMix). All measured Wynyard Fm detrital zircon dates can be attributed to zircon sources within 33 km of the sample location along the glacier’s flow path. This interpretation of a proximal detrital zircon provenance does not conflict with the popular interpretation made from sedimentological observations that the Wynyard Fm was deposited by a large, temperate outlet glacier or ice stream that flowed south-to-north across western Tasmania. Overall, a local first approach to glacial sediment provenance, though more challenging than direct comparisons between glacigenic sedimentary deposits, has the potential to elucidate the complex histories and flow paths of glacial sedimentary systems of all depositional ages.

Research on sedimentary facies of Guantao Formation in Shanjiasi area of Dongying depression, China

A magnitude-frequency analysis of rockslide-debris avalanche deposits was performed. Hummocks are conical mounds formed in debris avalanche deposits from the catastrophic sector collapse of a mountain (often volcanic) that represent relatively cohesive fragments of the mountain edifice. Examination of 17 debris avalanche deposits in Japan and the Philippines showed that, in general, the larger the magnitude of the hummocks, the smaller their frequency. Hummocks followed an exponential distribution: log10N(x) = a – bx, where N(x) is the cumulative number of hummocks with magnitude ≥ x and a and b are constants; x is equal to log10A, where A is the area of a hummock. The constants a and b were positively correlated. The value of b, which differs among avalanches and in this analysis ranged between 1 and 3, may be controlled by the mobility of the debris avalanche. Avalanches with higher mobility (relatively longer runout) have higher b and potentially produce more numerous fragments forming hummocks (i.e., higher a). From the above correlation, the magnitude-frequency relationship can be used to roughly estimate the original height of the collapsed volcanic body, if the runout distance of the rockslide–debris avalanche can be estimated with sufficient accuracy.