Sedimentary Structures and Magma Current Velocities in the Kalka Layered Intrusion, Central Australia

Examples of reworked sedimentary structures (asymmetric rippleforms, planar cross-stratification, and a scour structure) andmodified sedimentary structures (load casts) are described fromthe layered, gabbroic Kalka Intrusion in central Australia.The reworked structures are thought to be produced by the actionof vigorous, unidirectional, localized currents of convectionalorigin. Current velocities have been estimated at between 0.001and 5 cm sec^–1 for the lower flow regime structures, andgreater than 0.1 cm sec^–1 for the scour structure. Thesecompare well with theoretical convection velocities in magmas.Pyroxene/plagioclase mobility within basaltic magmas is greaterthan sand mobility in aqueous systems. The advent of the current activity which produced the scouris associated with a change from discontinuous to continuousnucleation (Goode, 1976), probably due to the increased turbulencein the crystallization zone. Erosional depths within unconsolidaredcrystal mushes that later became anorthositic adcumulates indicatethat melt diffusion can occur through at least 1 metre of cumulusaggregate.     

Sedimentary conditions and deposits of Akimiski Strait,James Bay,Canada

Akimiski Strait is a wide (17–20 km), shallow, emergent (0.70 cm per century) waterway in James Bay. It is localized in a saddle of a Paleozoic reef track, which has been enhanced and molded by Pleistocene glaciers. Drumlinoid ridges form the till cores of shoals and islets of the strait. The boundary conditions of the strait change throughout the year, as it is covered by ice for six months. During spring break-up the strait remains clogged with ice at its northern approach for several weeks, and acts as a large tidal inlet. It is during this period that most of the fluvial sediments are carried to sea. Other sediments are obtained by erosion of the Pleistocene tills and Holocene subtidal clays and silts exposed in nearshore areas. Resuspension of nearshore material is achieved through the action of wind-driven, short choppy waves and ice scour. Tides are the most important process for the redistribution of sediments along the coast, both flooding onshore and flooding and ebbing into and out from the strait generating locally powerful (2 m s^?1) reversing currents. Ice rafting and ice pushing are important processes in this frigid environment, particularly in upwind sides of shaols, and at/or near river mouths.Different intertidal sedimentary sequences develop as functions of sediment supply and exposure of the environments to ice, currents and waves. The eastern shores and the southern shoals of the strait develop pebble lags over till, covered by thin (5–20 cm) drapes of silty sand trapped and protected from erosion by algae. In these shores and in emerging small islands significant sedimentation (1–1.5 m thick) occurs in the marshes where the suspended load of tidal waters is trapped by vegetation. The western shores of the strait receive considerable amounts of sediment from large rivers and are affected by strong tidal longshore currents. Thick (3–4 m) and narrow tidal flats and marshes develop on the maincoast. The shoals of the northern part of the strait have characteristic sediments. Those near the western shore have thin (up to 80 cm) tidal silty sand deposits, locally heavily burrowed by Macoma balthica. Those strung across the northern approach to the strait have well-developed, thin, coarse sand dune fields, indicating a prevalent ebb flow out of the strait.     

Fate characteristics of nitrogen in runoff from a small agricultural watershed on the south of Huaihe River in China

Qualitative and quantitative evolution of the Swarna estuary, during the past 38 years (1967–2005), has been analysed by integrating the results of field surveys, satellite images, hydrodynamic modelling and topographic data in GIS context. Significant changes in erosion/accretion patterns of the estuarine banks, inlet configuration and adjacent spits, and origin, morphology, orientation and areal extent of fifteen braided islands have been estimated. Hydrodynamics of the region is studied through modelling, and probable flow pattern that is responsible for morphological changes is discussed. The simulated flow patterns indicate that current speeds are of the order of 10–20 cm/s inside the estuary and of the order of 40 cm/s at the mouth. The Right bank (Rb) of the estuary is subject to net erosion and the Left bank (Lb) is subject to net accretion. On an average, 20–30% of the area of all braided islands would be flooded, if the water level rises by 0.7 to 1.0 m. Islands of this estuary are morphologically very dynamic (migrating towards north, northeast and southwest directions) and subject to net accretion, whereas only one island (i.e., the Padu) has lost its major portion of landmass. A conceptual inverse distance weighted (IDW) interpolation model has been generated and evaluated possible flooding on the estuarine shoals and braided islands, due to heavy rainfall and/or sea-level rise. The model reveals that the possibility of flooding will be higher for those islands which are located close to the Rb than those close to the Lb.     

Investigation of groundwater flow in karst areas using component separation of natural potential measurements

 The natural (electrical) potential (NP) method – also known as self-potential, spontaneous potential and streaming potential (SP) – has been used to locate areas of groundwater flow in karst terrane. NP is the naturally occurring voltage at the ground surface resulting from ambient electrical currents within the earth. The measurement of NP can be used to characterize groundwater flow in karst terrane because electrical potential gradients are generated by the horizontal flow of water along fractures or conduits and the vertical infiltration of water into fractures or shafts. NP data from a site on the Mitchell Plain of southern Indiana, USA, revealed that NP data can be decomposed into three components: topographic effect, residual NP and noise. At this site, NP was inversely proportional to elevation, but the correlation varied with time. The topographic correction factor varied from –2.5 to –1.2 mV/m (NP change per unit elevation increase), with an average linear correlation coefficient (R) of 0.95. Because the site slopes toward an adjacent creek that is the local groundwater discharge zone, one possible explanation for this effect is a streaming-potential mechanism generated by groundwater movement toward the creek. The residual NP data revealed three negative anomalies at the survey area. Two of them coincide with sinkholes. A part of the third anomaly is coincident with a small valley, and concentrated infiltration does occur at this elevation in other valleys at the site, as evidenced by the existence of sinkholes. However, the dispersed, low-magnitude nature of the third anomaly does not prove the existence of concentrated groundwater recharge activity. Received: 18 March 1998 · Accepted: 27 April 1998     

Lithofacial complexes of quaternary deposits in the central and southeastern baltic sea

Geological and seismic profiling data (more than 25000 km of seismic profiles and about 1000 sediment sampling stations) collected during the last 30 yr by research vessels of the Shirshov Institute of Oceanology, Russian Academy of Sciences are summarized. Seismic records are directly correlated with sediment cores. The distribution map (scale 1 : 500000) of Quaternary lithofacial complexes corresponding to certain stages of the Baltic Sea evolution is compiled. The following four complexes are distinguished (from the base to the top): (I) moraine, with maximum thicknesses 60 and 170 m in valleys and ridges respectively: (II) varved clay of periglacial basins and from the Baltic Ice Lake (BIL), up to 25 m thick in depressions; (III) lacustrinemarine homogeneous clay with a thickness up to 4–8 m in depressions; (IV) marine sediments (mud, aleurite, coarse-grained deposits) accumulated in environments with intense bottom currents activity (thickness 2–4 m in the Gotland Basin, 4–6 m in the Gdansk Basin, and 10–20 m in fans and prodeltas). The Quaternary sequence is cut through by inherited valleys, where the thickest Holocene sediments are noted. Today, these valleys serve as routes of sediment transport to slope bases and central parts of basins. Outblows of deep gas (through faults and fractures) and diagenetic gas (from sediments) to the bottom surface also occur in the valleys. Sedimentation rates are higher in the Gdansk Basin (up to 100–120 cm/ka). Thick sand, aleurite, and mud bodies are accumulated here (about 15–20 m in the Visla River prodelta). The sedimentation rate is slower in the Gotland Basin (up to 50–60 cm/ka), where thin (2–4 m) sections of more fine-grained mud occur     

SCOUR RIPPLES IN THE LUDLOVIAN OF SOUTH RADNORSHIRE, WALES

Calcareous siltstone beds in the sub-littoral marine sedimentary rocks of the highest Ludlovian (Upper Whitcliffian) in south Radnorshire display symmetrical ripples with wave lengths around 30 cm. These structures are interpreted as having been formed by the deposition of calcareous silt layers in conformity with bottom surfaces previously scoured into a pattern of symmetrical, gently-rounded, crests and troughs; hence, they are termed scour ripples. There is some evidence of a longitudinal relationship between the scour ripples and the scouring and depositing currents involved in their formation.     

Sedimentology of the Ekwan Shoal,Akimiski Strait,James Bay,Canada

One of the steepest depositional coasts of western James Bay is found along the west shores of Akimiski Strait, north of the mouth of the Ekwan River. This shore receives considerable amounts of sediment during the spring break-up of the rivers. The sediments are stored on the steep narrow tidal flats and marshes, and in thinner (up to 80 cm) drapes on till-cored shoals that parallel and protect the coast. The low areas between the shoals and the mainland are swept and reworked by relatively powerful (2 m s^?1) reversing currents due to flooding and ebbing of tides into the strait.A series of distinct environments and sedimentary facies develop on this western coast and its antecedent longshore shoal. The outer part of the shoal is characterized by tidal bedding, Macoma balthica burrows and considerable ice scour. The inner part of the shoal has winnowed sand, the greatest abundance of Macoma, and well-developed flaser bedding. The longshore tidal channel separating the shoal from the mainland has coarse sand lags in the shallower parts and silty sand in deeper protected areas. The steep tidal flats develop laminated silty sands locally saturated and slumping toward the channel. The high saturation of the sediments inhibits colonization of the flats by Macoma. The narrow marshes have characteristic vegetation zonation, with Puccinellia phryganodes colonizing the lower marsh. The sedimentary sequence of the marsh displays irregular, bioturbated laminated sequences of silt, silty sand and organic matter.     

Beach and nearshore morphodynamic changes of the Tabarka coast,Northwest of Tunisia

Aerial photographs taken in the 1963 and 2001 and bathymetric charts, in conjunction with coastal processes are analyzed to assess changes in rate of shoreline position, seabed level, and seabed grain sizes along the Tabarka–Berkoukech beach at the north-western Tunisian coastline. The littoral cell of this beach, 12-km-long, is bounded by pronounced embayments and rocky headlands separated by sandy stretches. Although not yet very much undeveloped, this littoral is still experienced degradation and modification, especially along its shoreline, with significant coastal erosion at some places. Results obtained from analysis of shoreline position indicate that El Morjene Beach is experienced a landward retreat of more than −62 m, at a maximum rate of −1.64 m/year, whereas the El corniche beach is advanced about 16–144 m, at an average rate of 0.42 m–3.78 m/year. This beach accretion has been formed on the updrift side of the Tabarka port constructed between 1966 and 1970. Comparison of bottom contours deduced from bathymetric charts surveyed in 1881 and 1996 off the coastline between Tabarka Port and El Morjene Beach identifies erosional areas (sediment source) and accretionary zones (sediment sink). Erosion (0.87–4.35 cm/year) occurs between El kebir River Mouth and El Morjene beach, whereas accretion exists in the zone down wind of the port ranges between 0.87 and 5.21 cm/year. Morphological analyses of the shoreline and the seabed of the study nearshore area indicate that shoreline retreat corresponds to areas of seabed scour (sediment source) while shoreline accretion is associated with areas of seabed deposition (sediment sink). Furthermore, simulation of wave propagation using STWAVE model combined with grain size distributions of the seabed shows that fine sands are much dominated in depositional areas with low wave energy, whereas coarser sands in erosive zones with high wave energy. The results obtained suggest that the change of seabed morphology, wave height pattern and grain size sediment have a great influence on the modification of shoreline morphology and dynamics.     

Windstorms in the United States

High winds are one of the nation’s leading damage-producing storm conditions. They do not include winds from tornadoes, winter storms, nor hurricanes, but are strong winds generated by deep low pressure centers, by thunderstorms, or by air flow over mountain ranges. The annual average property and crop losses in the United States from windstorms are $379 million and windstorms during 1959–1997 caused an average of 11 deaths each year. Windstorms range in size from a few hundred to hundreds of thousands square kilometers, being largest in the western United States where 40% of all storms exceed 135,000 km². In the eastern United States, windstorms occur at a given location, on average, 1.4 times a year, whereas in the western US point averages are 1.9. Midwestern states average between 15 and 20 wind storms annually; states in the east average between 10 and 25 storms per year; and West Coast states average 27–30 storms annually. Storms causing insured property losses >$379 million and windstorms during 1959–1997 caused an average of 11 deaths each year. Windstorms range in size from a few hundred to hundreds of thousands square kilometers, being largest in the western United States where 40% of all storms exceed 135,000 km². In the eastern United States, windstorms occur at a given location, on average, 1.4 times a year, whereas in the western US point averages are 1.9. Midwestern states average between 15 and 20 wind storms annually; states in the east average between 10 and 25 storms per year; and West Coast states average 27–30 storms annually. Storms causing insured property losses >1 million, labeled catastrophes, during 1952–2006 totaled 176, an annual average of 3.2. Catastrophic windstorm losses were highest in the West and Northwest climate regions, the only form of severe weather in the United States with maximum losses on the West Coast. Most western storms occurred in the winter, a result of Pacific lows, and California has had 31 windstorm catastrophes, more than any other state. The national temporal distribution of catastrophic windstorms during 1952–2006 has a flat trend, but their losses display a distinct upward trend with time, peaking during 1996–2006.     

Sedimentology of the Minette oolitic ironstones of Luxembourg and Lorraine: a Jurassic subtidal sandwave complex

The oolitic ironstones of the Minette were deposited during Toarcian/Aalenian times in a nearshore environment of the Paris Basin. The sedimentary sequence comprises up to 13 coarsening upward depositional cycles. The development of the cycles and different facies types are described. The iron ooids accumulated in a subtidal environment under the effects of tidal currents. Sand waves, which form an important part of the Minette sediments, were deposited under both time-velocity symmetrical and time-velocity asymmetrical tides. From the study of their internal structures the time-velocity patterns of the currents, current speeds (up to 0±9m s^?1) and net transport rates have been estimated (29 g m^?1 s^?1 in the case of large-scale sand waves controlled by time-velocity symmetrical tides). Sand wave heights and calculated near-bed current speeds suggest a mesotidal regime. Sedimentary facies include large-scale and waves, subtidal shoals with channels and an offshore muddy shelf. Conclusions as to bathymetry are drawn from ichnofaunal associations and from the study of wave ripple marks. Finally a depositional model of the Minette iron formation is proposed which may be applicable to other oolitic ironstones.     

RETRACTED ARTICLE: Space and time distributions of major winter storms in the United States

Winter storms are a major weather problem in the United States and their losses have been rapidly increasing. A total of 202 catastrophic winter storms involving ice storms, blizzards, and snowstorms, each causing >$5 million in damages, occurred during 1949–2003, and their losses totaled $35.2 billion (2003 dollars). Catastrophic winter storms occurred in most parts of the contiguous United States, but were concentrated in the eastern half of the nation where 88% of all storm losses occurred. They were most frequent in the Northeast climate district (95 storms), and were least frequent in the West district (14 catastrophic storms). The annual average number of storms is 3.7 with a 1-year high of nine storms, and one year had no storms. Temporal distributions of storms and their losses exhibited considerable spatial variability across the nation. For example, when storms were very frequent in the Northeast, they were infrequent elsewhere, a result of spatial differences in storm-producing weather conditions over time. The time distribution of the nation’s 202 storms during 1949–2003 had a sizable downward trend, whereas the nation’s storm losses had a major upward trend for the 55-year period. This increase over time in losses, given the decrease in storm incidences, was a result of significant temporal increases in storm sizes and storm intensities. Increases in storm intensities were small in the northern sections of the nation, but doubled across the southern two-thirds of the nation, reflecting a climatic shift in conditions producing intense winter storms.     

The importance of physical and biogenic structure to juvenile fishes on the shallow inner continental shelf

Fish-habitat relationships on the shallow inner continental shelf were quantified with video sled and metered beam trawl on Fenwick and Weaver shoals offshore of Maryland and Delaware, U.S. These areas provide megascale physical relief and habitat complexity, but for juvenile fishes, mesoscale and microscale habitat is very important particularly as refuge from predation. At these smaller scales, much of the relief on the inner continental shelf is contributed by bedforms or sand waves and biogenic structures such as tubes, shell beds, or pits. A quantitative association for juvenile fishes between and within benthic habitats was found and related primarily to bedform size and amount of biogenic structure. The incidence of fishes was about four-times higher for large bedforms (> 30 cm wavelength and about 10 cm crest height) relative to smaller bedforms (<30 cm wavelength and about 5 cm crest height). For biogenic structure, going from high patch-mat tube densities to lower densities or no biogenic structure increased fish incidence by 5.4 and 3.3 times, respectively. The significant relationships of fishes with bedform size and density of biogenic structure indicated that seemingly small differences in physical structure of a habitat can make the difference between unacceptable and essential habitat for juvenile fishes. Proximity of complex and simple habitats was important in the diel use of habitat and in balancing pressure of refuge from predation provided by complex habitats with foraging for increased resources available in simpler habitats. During the day, spatially complex habitats comprised ofDiopatra andAsabellides tube mats had about twice as many fishes relative to bare sandy habitats (8.3–9.9 versus 4.0–4.1 fishes 100 m⁻², respectively). At night, the pattern was reversed with more fishes present in the bare sandy habitats (12.4–13.5 versus 5.6–8.7 fishes 100 m⁻²). Some fish, such asAmmodytes spp., were very habitat specific and occurred only on dynamic coarser sands near the top of the shoals. Others, such asUrophycis regia, showed less habitat preference and occurred in all habitats during both day and night. Combining the effects of physical relief and biogenics, the habitat with the highest incidence of fishes had large bedforms with some biogenic structure. More emphasis needs to be placed on quantifying the relationship between fishes and their habitats for the fisheries management concept of essential fish habitat to develop into an effective tool on the inner continental shelf. The juvenile life history stages need to be emphasized because fish-habitat interactions are the strongest for these stages and may be the most ecologically important.     

Tsunami-induced large-scale scour-and-fill structures in Late Albian to Cenomanian deposits of the Grajaú Basin, northern Brazil

Late Albian to Cenomanian upper shoreface deposits from the Grajaú Basin, northern Brazil, consist of well‐sorted, very fine‐ to fine‐grained sandstones with swaley, trough, tabular and minor hummocky cross‐stratification. A striking feature of these deposits is the abundance of large‐scale scour‐and‐fill structures, which consist of regularly spaced, repetitive, very shallow swales with either symmetrical or asymmetrical profiles, arranged along an undulose surface or as a succession of superimposed troughs. The sediment filling these scours is characterized by very fine‐grained sandstone with gently undulose, near‐parallel lamination to very low‐angle dipping cross‐stratification intergraded with swaley and hummocky cross‐stratification. The nature of the scours and the sedimentary structures of their fills reveal the action of combined flows, which are hydrodynamically similar to those developed during storms. However, it is speculated that the combined flows responsible for the genesis of these structures were formed by tsunami waves enhanced by tsunami‐induced ebb currents and/or tidal currents. This interpretation is proposed on the basis of several lines of reasoning: (1) palaeogeographic reconstructions of the study area during the late Cretaceous show that it was outside the belt favourable for the development of storms; (2) comparison of the scour‐and‐fill structures with stratigraphically correlatable deposits exposed north of the study area, where similar features occur in association with abundant seismically induced, soft‐sediment deformation structures; and (3) the presence of several styles of soft‐sediment deformation features (i.e. convolute lamination, bed collapse, large‐scale folds, massive bedding, sand‐filled fractures and diastasis cracks) are suggestive of synsedimentary seismic activity in Cretaceous deposits located in and near to the study area. This study proposes that episodic, high‐amplitude tsunami waves, enhanced by tsunami‐induced ebb currents, develop powerful flows capable of producing complex patterns of erosion and sedimentation, which may be represented by scour‐and‐fill structures similar to those described here.     

Zoning of platinum group mineral assemblages in the UG2 chromitite determined through in situ SEM-EDS-based image analysis

In situ scanning electron microscopy–energy dispersive X-ray spectrometry analysis of platinum group minerals (PGM) and base metal sulfides in the UG2 chromitite shows that this ore body is zoned along at least ∼6 km of strike. The uppermost part of the UG2 chromitite, referred to as the leader seam, is ∼16 cm thick and has a PGM assemblage that is dominated by PGE arsenides, sulpho-arsenides, and alloys (∼70 vol.% of all PGM), which are typical secondary PGM assemblages in other segments of UG2. This is the first time such laterally persistent secondary assemblages have been identified in the UG2 chromitite, as previously, they were only known to occur adjacent to transgressive fluid-bearing structures (e.g., pipes, faults). The underlying main seam is thicker (one to nine seams totaling ∼130 cm) and has a PGM assemblage that consists mostly of Pt sulfide, Pt–Pd sulfide, Pt–Rh–Cu sulfide, laurite, and Fe–Pt alloys (∼85 vol.% of all PGM), typically regarded as primary magmatic constituents of UG2 chromitite. There are, however, some subtle vertical changes in the PGM assemblages of the main seam that include the occasional presence of secondary assemblages in the top and bottom parts. The origin of these secondary PGM assemblages is related to alteration by hydrothermal fluids and/or fluid-rich melts that infiltrated during crystallization of the UG2 and may possibly have been derived from the UG2 chromitite itself.     

Reassessing the tsunami risk in major ports and harbors of California I: San Diego

We assess tsunami hazards in San Diego Bay, California, using newly identified offshore tsunami sources and recently available high resolution bathymetric/topographic data. Using MOST (Titov and Synolakis, J Waterways Port Coastal Ocean Eng ASCE 124(4):57–171, 1998), we simulate locally, regionally and distant-generated tsunamis. Local tsunami source models use more realistic fault and landslide data than previous efforts. With the exception of the Alaska-Aleutian Trench, modeling results suggest that local sources are responsible for the largest waves within the San Diego Bay and Mission Bay. Because San Diego Bay is relatively well protected by North Island and the Silver Strand, the wave heights predicted are consistently smaller inside the harbor than outside. However, historical accounts, recent tsunamis and our predictions show that San Diego Bay is vulnerable to strong tsunami induced currents. More specifically, large currents are expected inside the harbor for various distant and local tsunami sources with estimated flow velocities exceeding 100 cm/s. Such currents have been damaging to harbor facilities, such as wharves and piers, and may cause boats to break from moorings and ram into adjacent harbor structures, as observed in recent historic tsunamis. More recently, following the M _w 8.8 February 27, 2010 Chile earthquake, tsunami-currents damaged docks/piers in Shelter Island confirming our findings. We note that the first generation of inundation maps in use in San Diego County by emergency management was based on much larger “worst case but realistic scenarios” (Synolakis et al. 2002a), which reflected the understanding of offshore hazards pervasive ten years ago. Large inundation and overland flow depths were observed primarily in local tsunami source simulations. In particular, locally induced tsunamis appear capable to overtop the Silver Strand. The results suggest that further work needs to be carried out with respect to local tsunami sources as they seem to have worse impact in the San Diego region than previously thought but probably low probability of occurrence. We also predict that a coastal community can be devastated simultaneously by large waves inundating shores and large currents in locations with small flow depths.     

Possible effects of the 2004 and 2005 hurricanes on manatee survival rates and movement

Prior research on manatee (Trichechus manatus latirostris) survival in northwest Florida, based on mark-resighting photo-identification data from 1982–1998, showed that annual adult apparent survival rate was significantly lower during years with extreme storms. Mechanisms that we proposed could have led to lower estimates included stranding, injury from debris, being fatally swept out to sea, or displacement into poorly monitored areas due to storm-generated longshore currents or storm-related loss of habitat. In 2004 and 2005, seven major hurricanes impacted areas of Florida encompassing three regional manatee subpopulations, enabling us to further examine some of these mechanisms. Data from a group of manatees tracked in southwest Florida with satellite transmitters during Hurricanes Charley, Katrina, and Wilma showed that these animals made no significant movement before and during storm passage. Mark-resighting data are being collected to determine if survival rates were lower with the 2004 and 2005 storms.     

Geomagnetic activity control on VHF scintillations over an Indian low latitude station, Waltair (17.7‡N, 83.3‡E, 20‡N dip)

Using the data of amplitude scintillations recorded at 244 MHz from the geostationary satellite, FLEETSAT (73‡E) at a low latitude station, Waltair (17.7‡N, 83.3‡E, 20‡N dip), during the increasing sunspot activity period of 1997–2000, the effect of the geomagnetic storms on the occurrence of ionospheric scintillations has been studied. A total of 60 SC storms studied during this period, following the Aarons’ criterion, reveals that the local time of onset of the recovery phase of the geomagnetic storms play an important role in the generation or inhibition of the ionospheric irregularities. Out of the 60 storms studied, nearly 60 to 70% satisfied the categories I, II and III of Aarons’ criteria. However, in the remaining 30 to 40% of the cases, no consistent results were observed. Thus, there is a necessity for further investigation of the effect of geomagnetic storms on ionospheric irregularities, particularly with reference to the altitude variations of the F-layer (h’F) relating to the changes in the local electric fields.     

Quaternary glaciation of the North Slope of Karakorum mountains

Three kinds of moraines can be found in the Muztagh valley on the N slope of Mount K2, Karakorum: an old calco-cement moraine lying at the altitude of 5000 m asl, a hilly moraine lying at the altitude of 4200–4800 m asl and a new lateral moraine, lying on both sides of the present river valley. According to the moraines’ geomorphology, they are referred to the Middle Pleistocene Glaciation, the Late Pleistocene Glaciation and the Post-Glacial Period respectively. The lowest level of glacial cirques at 4200–4000 m asl, corresponding to the largest Glaciation, belongs to the Middle Pleistocene (Riss). The ancient cirques at this altitude in the Shaksgam and Yargand valleys are poorly preserved while at the piedmont of the West Kunlun mountains they are represented in better shape. This means that these ancient cirques had been submerged and almost removed by the main ice flow of the valleys. Old cirques, however, are well shaped (or reshaped) where associated with younger cirques at 4600 m als; they could be considered as the product of the Last Glaciation (Würm). Thus, the equilibrium line altitude (ELA) decreased to 1600 m during the Riss Glaciation and to 1000 m during the Würm Glaciation. On the basis of the ELA decrease and existence of complex morainic deposits found at the piedmont of the West Kunlun mountains at about 2200 m asl, the author adheres to the opinion that Riss Glaciation had developed an ice cover (ice sheet), with the central ice area located in Karakorum and reaching up to the high peaks of the Kunlun mountains, and down to the piedmont region. During the Last Glaciation an immense ice cap covered the upper parts of the Shaksgam and Yarkant valleys. The paper also deals with the relations between glaciations and tectonic uplift, indicating that topographic and climatic conditions were favourable for the large-scale ice development in the Middle and Late Pleistocene. The uplift may have reached 600–800 m during the Postglacial period. The uplift rates are often reflected by the glaciostatic in the Postglacial Age.     

Micromorphology of ice keel scour in pebbly sandy mud and fine‐grained sands: Scarborough Bluffs,Ontario, Canada

The keels of icebergs and ice‐pressure ridges plough through unconsolidated sea/lake sediments gouging out long grooves known as ice keel scour marks. Although the surface and (more recently) subsurface morphology of scours are well‐documented, little is known of the effect of grain size on the detectability, style and intensity of sub‐scour deformation. This investigation macroscopically and microscopically (two‐dimensional thin sections) examines suspected ice keel scour in: (i) glaciolacustrine pebbly sandy mud and (ii) fine‐grained sands at Scarborough Bluffs, Ontario, Canada. In this investigation, there is an almost identical suite of deformation structures (individual structures and overprinted structural patterns) to those identified in iceberg‐scoured clays from former Glacial Lake Agassiz (Manitoba, Canada); this confirms that deformation in the pebbly sandy mud and fine‐grained sands at Scarborough Bluffs is likely to be indicative of ice keel scour. Discrete differences in the detectability, style and intensity of deformation between the Scarborough Bluffs and Glacial Lake Agassiz sediments are probably a function of grain size in response to ice keel scour. This research provides additional information on the types of structures that are associated with sediment deformation by processes of ice keel scour in a variety of grain sizes. This information is particularly valuable to inform palaeoenvironmental reconstruction and offshore engineering in areas where ice keel scour occurs in a variety of grain sizes. It also demonstrates the potential value of micromorphology where, for example, the study of cores is necessary.     

Meteorological factors affecting the speed of movement and related impacts of extratropical cyclones along the U.S. east coast

The speeds of historical cool-season extratropical cyclones along the U.S. east coast, hereafter East Coast Winter Storms (ECWS), occurring during the period from 1951 to 2006 were computed. Average storm speed was 13.8 ms⁻¹ with stronger storms generally moving faster than weaker storms and faster storms forming during the midwinter months (December–March). There was no clear trend in ECWS speed during the time period, although considerable season-to-season variability was present. The monthly and seasonal variations in storm speed could not be attributed to the El Ni?o-Southern Oscillation or North Atlantic Oscillation (NAO) alone. However, the speed of ECWS was considerably slower when both El Ni?o and the negative phase of NAO occurred simultaneously. Characteristic patterns in the upper levels of the atmosphere, specifically 300 hPa zonal winds and 500 hPa geopotential heights, were present during periods when ECWS speeds were among the slowest (and separately fastest). For slow storm speed, these patterns also prevailed during months in which El Ni?o and negative NAO phase occurred. These patterns were also present during months with extended runs of high oceanic storm surge. This provides a qualitative link between the atmospheric conditions associated with slow storms and potentially high coastal storm surge impacts. Among the prime consequences of ECWS speed are extended periods of high storm surge, mainly due to slow-moving storms. The sustained high tidal levels often lead to substantial damage caused by coastal flooding, overwash, and beach erosion.