a geotechnical correction for post depositional sediment compression examples from the forth valley scotland fine grained sediments usually suffer post depositional compression compaction which reduces bed thickness and lowers the elevations of sample positions and marker horizons this reduction has been calculated for two general cases using geotechnical theory and a correction decompaction factor is presented that can be applied to many field situations its use is illustrated by two examples from the clay sediments of the claret formation of the forth valley in the first the correction is calculated for 14c samples from the bothkennar research site near grangemouth and the effect on the reconstruction of water depths is discussed in the second example corrections are obtained for published sea level index points from former shorelines in the forth valley using a method for a postiori estimation of geotechnical data general conclusions are drawn between the size of the correction and the sample position relative to the local depocentre some applications to palaeotidal modelling are also suggested 1998 john wiley sons ltd

patterns and rates of erosion produced by high energy wave processes on hard rock headlands the grind of the navir shetland scotland abstract the grind of the navir is an ignimbrite headland on the exposed atlantic coast of the shetland islands scotland during storms offshore wave heights exceed 20 m and deep water close inshore allows high energy waves to impact on these cliffs the cliff top at 15 m above sea level is awash with wave water when wave heights exceed 8 m a condition met in storms in most years detailed mapping ground photography and patterns of lichen colonisation and growth allow the processes patterns and rates of erosion to be assessed on different parts of the headland over the past 100 years recent fractures in the rock of the cliff face and top indicate that wave impact forces exceed the 1 5 kpa tensile strength of the rock and fresh sockets low on the cliff face record the removal of fracture bounded blocks that are lost to seaward on the upper part of the cliff face upward moving water flow is capable of removing blocks from both vertical faces and stepped overhangs clefts in the cliff face are extended inwards and upwards by crack propagation and block removal leading to the development of slot caves the movement of waves across the cliff top in fast moving bores quarries blocks from the cliff face close to the edge and from rock steps on the cliff top promoting further rock fracturing socket sizes and block characteristics indicate that blocks of 1 m 3 are rotated from sockets on the cliff top platform and carried landwards for up to 60 m to be deposited in a series of boulder ridges on the cliff top multiple boulder movements during a storm in january 2005 generated impact marks and orientated striations that allow the pattern of water movement to be reconstructed across considerable areas of cliff top the average rate of erosion at the grind is estimated at 1 3 6 0 mm yr on the cliff face and 5 mm yr on the cliff top although erosion rates vary in both time and space although block movement on the cliff top occurs in most years erosion of rock by block removal is most active during major storms nevertheless some parts of the cliff top and face remain blackened by lichen and so have experienced little recent erosion over the last 70 years or so although erosion occurs at the base of the cliffs in recent decades it has been concentrated on upper part of the cliff face and top cliff top erosion is most intense where stepped geos act as channels for waves to access the cliff top the most active features on the cliff top are the boulder ridges where substantial changes can be traced to storms over the past century unlike conventional models of cliff erosion where erosion is concentrated by wave attack at the waterline wave impacts on this headland may occur on any part of cliff face and top and appear particularly effective on the upper cliff and cliff top platform

cliff top storm deposits on banneg island brittany france effects of giant waves in the eastern atlantic ocean this study is based on the morphosedimentary analysis of the cliff top storm deposits accumulated on the coast of banneg island located in the archipelago of molene brittany france these ctsds comprise large tabular clasts quarried from the upper part of the cliff and the backing scoured platform by giant oceanic storm waves impacting directly the western coast of the island an analysis of the distribution and the geomorphology of these accumulations were carried out using the dgps topographic surveys most of the clasts are organised into imbricate boulder clusters or ridges deposited between 7 5 and 14 5 masl 52 accumulations were inventoried from the north to the south of the island representing a global volume of 1000 m3 the median size of the clasts calculated is equivalent to 0 8 0 6 0 4 m and a weight of 0 6 t the largest one measuring 5 3 3 9 0 5 m 32 t is located in the centre of the island ridge 28 it has been deposited 14 m inland from the edge of the cliff at the elevation of 9 m sediment analysis shows that clast sizes become smaller with increasing distance from the shoreline but there is no relationship between the sorting and the distance inland a study of the hydrodynamic conditions inducing clast transport was undertaken by an analysis of the wave data from the 1989 to the 1990 winter storms models of wave runup indicate that their highest water levels may have reached up to 19 masl 5 to 10 m higher than the top of the cliff submersion by giant storm waves has been more important and frequent in the centre and the south of the island wave data over the 1979 to the 2007 period shows that no events as powerful as those of the 1989 to the 1990 winter were recorded during the last 30 years yet it appears that the 1979 1990 decade was characterized by important morphogeneous events while the following period 1990 2007 has experienced a sharp decrease in storm events these variations could be attributed to the inversion from a negative towards a positive phase in the north atlantic oscillation index

geology mineralogy and stable isotope geochemistry of the kabwe carbonate hosted pb zn deposit central zambia abstract the carbonate hosted kabwe pb zn deposit central zambia has produced at least 2 6 mt of zn and pb metal as well as minor amounts of v cd ag and cu the deposit consists of four main epigenetic pipe like orebodies structurally controlled along ne sw faults sphalerite galena pyrite minor chalcopyrite and accessory ge sulphides of briartite and renierite constitute the primary ore mineral assemblage cores of massive sulphide orebodies are surrounded by oxide zones of silicate ore willemite and mineralized jasperoid that consists largely of quartz willemite cerussite smithsonite goethite and hematite as well as numerous other secondary minerals including vanadates phosphates and carbonates of zn pb v and cu galena sphalerite and pyrite from the pb zn rich massive orebodies have homogeneous negative sulphur isotope ratios with mean 34 s cdt permil values of 17 75 0 28 1 16 54 0 0 27 and 15 82 0 25 respectively the zn rich and pb poor no 2 orebody shows slightly heavier ratios of 11 70 0 5 34 s for sphalerite and of 11 91 0 71 34 s for pyrite the negative sulphur isotope ratios are considered to be typical of sedimentary sulphides produced through bacterial reduction of seawater sulphate and suggest a sedimentary source for the sulphur carbon and oxygen isotope ratios of the host dolomite have mean 13 c pdb and 18 o smow values of 2 89 and 27 68 respectively which are typical of marine carbonates the oxygen isotope ratios of dolomite correlate negatively to the sio 2 content introduced during silicification of the host dolomite the depletion in 18 o in dolomite indicates high temperature fluid rock interaction involving a silica and 18 o rich hydrothermal solution two types of secondary fluid inclusions in dolomite both of which are thought to be related to ore deposition indicate temperatures of ore deposition in the range of 257 to 385 and 98 to 178 c respectively the high temperature fluid inclusions contain liquid vapour solid phases and have salinities of 15 to 31 eq wt nacl whereas the low temperature inclusions consist of liquid vapour with a salinity of 11 5 eq wt nacl fluid transport may have been caused by tectonic movements associated with the early stages of the pan african lufilian orogeny whereas ore deposition within favourable structures occurred due to changes in pressure temperature and ph in the ore solution during metasomatic replacement of the host dolomite the termination of the kabwe orebodies at the mine club fault zone and observed deformation textures of the ore sulphides as well as analysis of joint structures in the host dolomite indicate that ore emplacement occurred prior to the latest deformation phase of the neoproterozoic lufilian orogeny

characteristics and hydrodynamics of boulders transported by storm waves at kudaka island japan abstract this study investigates the size position and the long axis orientation of 210 boulders at kudaka island japan these boulders were deposited from the reef crest to the slope of the back reef moat distributed within 275 m from the reef edge most boulders were rectangular to ellipsoidal without sharp broken edges they are reef rock fragments estimated as

cliff top megaclast deposits of ireland a record of extreme waves in the north atlantic storms or tsunamis past occurrences of major tsunami in the global record have often been inferred from the presence of megaclast accumulations at significant heights above sea level which sometimes exhibit a pronounced seaward directed imbricate fabric the aran islands off the west coast of ireland exist in a marine environment which is totally unprotected from the most extreme sea states encountered in the north atlantic spectacular megaclast accumulations are found along the tops of vertical cliffs on these islands the elevation of these deposits varies from 0 m to 50 m above mean sea level and they include clasts weighing 250 tonnes at sea level over 117 tonnes at 12 m and 2 9 tonnes at 50 m above sea level imbrication measurements on these megaclasts indicate a well defined and consistent mean direction from the southwest for the emplacing waves one that is consistent with the prevalent storm wind direction for the area the megaclast accumulations are subject to episodic and on going erosion by cliff retreat but the existing accumulations are estimated to record events since at least 1839 recent emplacement and reworking is evidenced by trapped plastic detritus within the deposits and eyewitness accounts of large storms during which clasts have been emplaced similar deposits are found on the exposed coasts of the shetland and orkney islands off scotland there is at present no evidence of any tsunami in recorded history affecting the western irish and scottish coasts other than those generated by the lisbon earthquake of 1755 where the wave effects were slight thus the presence of megaclast accumulations at significant heights above sea level on exposed coasts and exhibiting imbrication should not be used as a definitive criterion for the past occurrence of tsunami these deposits attest to extreme wave conditions occasionally encountered in the north atlantic and act as a record of such events extending back at least 160 years such data on extreme wave conditions are essential for the prediction of the effects of deepwater waves on structures such as offshore drilling platforms

the geotectonic environment of zambian copper cobalt mineralization suggestions that the ore shale of the lower roan group is part of a series of sedimentary fades produced by the north easterly transgression of the sea over dominantly arenaceous strata of littoral deltaic lacustrine and continental origin have been viewed with scepticism by the author the lack of proven transition facies from silty carbonaceous argillites of the type found close to the south western limits of the ore shale in the zambian copperbelt to dolomites found further to the sw has tended to accentuate this feeling the intensity of exploration drilling in these areas must imply that whatever the cause the cut out of the ore shale is rapid at the same time a 9normal9 lower roan succession of the chambishi type suddenly becomes attenuated and dolomites and dolomitic chloritic schists are found immediately overlying argillaceous gritty sandstones conglomerates and arkosic quartzites characteristic of footwall formations locally this contact may be reddened porous and brecciated amphibolite bodies of the type normally found at a much higher stratigraphic level in the upper roan group are present a short distance above this contact it is thus proposed that this feature represents a hiatus in the succession and that all rocks from the ore shale to the top of the lower roan and possibly into the base of the upper roan are missing due to non deposition and or erosion this interruption of the succession coincides with the western cut out of the ore shale from the konkola dome in the nw down to the western end of the roan basin in the s in view of various authors9 contention that the zambian copperbelt is the site of an ancient aulacogen the above observations take on an important genetic significance the present paper thus reviews the location of copper cobalt mineralization in relation to sedimentary facies changes and cut outs structural features and amphibolitic bodies and proposes a geotectonic model for the copperbelt which it is hoped provides a more satisfactory and comprehensive explanation for the facts this model also provides a source for the metals which were converted to sulphides by diagenetic processes it is believed that the complex mineral chemistry of the ore shale associated ores and in particular the presence of localized concentrations of mo co ag as bi and te bearing phases is best explained by high level seepage of magmatically enriched hydrothermal solutions along precambrian rift systems and associated fractures these metals were either dispersed by wave and current action in the sedimentary environment or were concentrated by porosity and physico chemical and bacteriogenic controls in the diagenetic environment

field signatures of the se asian mega tsunami along the west coast of thailand compared to holocene paleo tsunami from the atlantic region the andaman sumatra tsunami of dec 26 2004 was by far the largest tsunami catastrophe in human history an earthquake of 9 to 9 3 on the richter scale the extension of waves over more than 5000 km of ocean and run ups up to 35 m are its key features these characteristics suggest significant changes in coastal morphology and high sediment transport rates a field survey along the west coast of thailand phuket island khao lak region including some similan islands nang pha mangrove areas and phi phi don islands seven to nine weeks after the tsunami however discovered only small changes in coastal morphology and a limited amount of dislocated sediments restricted to the lower meters of the tsunami waves this is in striking contrast to many paleo tsunami s events of the atlantic region explanations for this discrepancy are sought in a mechanics of the earthquake a rather slow shock impulse on the water masses over the very long earthquake zone b shallow water in the earthquake zone and c bathymetry of the foreshore zone at the impacted sites shallow water west of thailand has diminished wave energy significantly the differences in geomorphological and sedimentological signatures of this tsunami compared with many paleo tsunami worldwide makes it unsuitable to be used as a model for old and future tsunami imprints by an event of this extreme energy and extension

distribution origin and transport process of boulders deposited by the 2004 indian ocean tsunami at pakarang cape thailand abstract the tsunami of 2004 in the indian ocean transported thousands of meters long boulders shoreward at pakarang cape thailand we investigated size position and long axis orientation of 467 boulders at the cape most of boulders found at the cape are well rounded ellipsoid in shape without sharp broken edges they were fragments of reef rocks and their sizes were estimated to be 3 22 7t the distribution pattern and orientation of long axis of boulders reflect the inundation pattern and behavior of the tsunami waves it was found that there is no clear evidence indicating monotonous fine coarse shoreward trends of these boulders along each transect line on the other hand the large boulders were deposited repeatedly along the three arcuate lines at the intertidal zone with a spacing of approximately 136m interval this distribution pattern may suggest that long lasting oscillatory flows might have repositioned the boulders and separated the big ones from small no boulders were found on land indicating that the hydraulic force of the tsunami wave rapidly dissipated on reaching the land due to the higher bottom friction and the presence of a steep slope we further conducted numerical calculation of tsunami inundation at pakarang cape according to the calculation the sea receded and the major part of the tidal bench area with boulders at present was exposed above the sea surface before the arrival of the first tsunami wave the first tsunami wave arrived at the cape from west to east at approximately 130min after the tsunami generation and then inundated inlands our calculation shows that tsunami wave was focused around the offshore by a small cove at the reef edge and spread afterwards in a fan like shape on the tidal bench the critical wave velocities necessary to move the largest and average size boulders by sliding can be estimated to be approximately 3 2 and 2 0m s respectively the numerical result indicates that the maximum current velocity of the first tsunami wave was estimated to be from 8 to 15m s between the reef edge and approximately 500m further offshore this range is large enough for moving even the largest boulder shoreward these suggest that the tsunami waves that were directed eastward struck the reef rocks and coral colonies originally located on the shallow sea bottom near the reef edge and detached and transported the boulders shoreward

geochemistry and geotectonic setting of late proterozoic katangan basic rocks from kibambale in central shaba zaire the late proterozoic katangan basic rocks dolerites and basalts outcropping at kibambale in central shaba zaire are classified as extension related tholeiites the concentrations of immobile major and trace elements resemble those encountered in phanerozoic enriched oceanic ridge basalts e morb emplaced in incipient oceanic rifts such as red sea and tadjura gulf troughs this conclusion is also sustained by elemental ratios which are morb like multielement chondrite and morb normalized patterns sedimentological data especially the shallow water conditions which prevailed during the deposition of lower kundelungu tillite in which these basic rocks are interstratified and the geological and structural framework notably the emplacement of these igneous rocks in a basin not distant from the kibaran continental land mass

magnitude and frequency of extra tropical north atlantic cyclones a chronology from cliff top storm deposits cliff top storm deposits ctsds are known to occur on cliffs at elevations of up to 50 m above sea level at exposed sites on the deep water coasts of the british isles eye witness accounts and time series field mapping of ctsds demonstrate their formation over the historical period and their continued modification during major storms with ctsds burying a range of modern human derived debris older deposits show surface lichen growth and weathering effects that relate to the relative age of ctsds over longer time spans buried sand and peat deposits provide dates on phases of ctsd emplacement and mobilisation and so provide an indication of the frequency and timing of the most severe storms two adjacent sites in shetland provide a combination of 14c dates on peat buried beneath storm deposited boulders 14c dates on marine shells buried inside ctsd boulder ridges and optically stimulated luminescence osl ages on sands intercalated with storm derived boulders although the precision is low this evidence identifies phases of exceptional storm activity spanning approximately 400 550 700 1050 1300 1900 and since 1950 ad by the very nature of cliff top erosion and deposition these records are fragmentary yet the timeline of major storms recorded in the shetland cliffs matches fairly well with the more general record of storminess in the north atlantic derived from the sea salt record in the gisp2 ice core as such ctsds represent an overlooked archive of storm sedimentation with the potential to elucidate local storm chronologies as well as informing debate surrounding the palaeo tempestology and impact of major cyclones and hurricanes

evidence for three north sea tsunamis at the shetland islands between 8000 and 1500 years ago abstract coastal fen and lake deposits enclose sand layers that record at least three holocene tsunamis at the shetland islands the oldest is the well known storegga tsunami ca 8100 cal yr bp which at the shetlands invaded coastal lakes and ran up peaty hillsides where it deposited sand layers up to 9 2 m above present high tide level because sea level at ca 8100 cal yr bp was at least 10 15 m below present day sea level the runup exceeded 20 m in two lakes we also found deposits from a younger tsunami dated to ca 5500 cal yr bp the sediment facies are similar to those of the storegga tsunami rip up clasts sand layers re deposited material and marine diatoms runup was probably more than 10 m yet another sand layer in peat outcrops dates to ca 1500 cal yr bp this sand layer thins and fines inland and was found at two sites 40 km apart and traced to ca 5 6 m above present high tide the oldest tsunami was generated by the storegga slide on the norwegian continental slope we do not know what triggered the two younger events

origin of the nchanga copper cobalt deposits of the zambian copperbelt the zambian copperbelt forms the southeastern part of the 900 km long neoproterozoic lufilian arc and contains one of the world s largest accumulations of sediment hosted stratiform copper mineralization the nchanga deposit is one of the most significant ore systems in the zambian copperbelt and contains two major economic concentrations of copper and cobalt hosted within the lower roan group of the katangan supergroup a lower orebody copper only and upper orebody copper and cobalt occur towards the top of arkosic units and within the base of overlying shales the sulfide mineralogy includes pyrite bornite chalcopyrite and chalcocite although in the lower orebody sulfide phases are partially or completely replaced by malachite and copper oxides carrollite is the major cobalt bearing phase and is restricted to fault propagation fold zones within a feldspathic arenite hydrothermal alteration minerals include dolomite phlogophite sericite rutile quartz tourmaline and chlorite quartz veins from the mine sequence show halite saturated fluid inclusions ranging from 31 to 38 wt equivalent nacl with homogenisation temperatures thtot ranging between 140 and 180 c diagenetic pyrites in the lower orebody show distinct relatively low 34s ranging from 1 to 17 whereas arenite and shale hosted copper and cobalt sulfides reveal distinctly different 34s from 1 to 12 for the lower orebody and 5 to 18 for the upper orebody there is also a clear distinction between the 34s mean of 12 1 3 3 n 65 for the upper orebody compared with 5 2 3 6 n 23 for the lower orebody the 13c of dolomites from units above the upper orebody give 13c values of 1 4 to 2 5 consistent with marine carbon however dolomite from the shear zones and the alteration assemblages within the upper orebody show more negative 13c values 2 9 to 4 0 and 5 6 to 8 3 respectively similarly shear zone and upper orebody dolomites give a 18o of 11 7 to 16 9 compared to lower roan dolomites which show 18o of 22 4 to 23 0 two distinct structural regimes are recognized in the nchanga area a weakly deformed zone consisting of basement and overlying footwall siliciclastics and a moderate to tightly folded zone of meta sediments of the katangan succession the fold geometry of the lower roan package is controlled by internal thrust fault propagation folds which detach at the top of the lowermost arkose or within the base of the overlying stratigraphy and show vergence towards the ne faulting and folding are considered to be synchronous as folding predominantly occurred at the tips of propagating thrust faults with local thrust breakthrough the data from nchanga suggests a strong link between ore formation and the development of structures during basin inversion as part of the lufilian orogeny sulfides tend to be concentrated within arenites or coarser grained layers within shale units suggesting that host rock porosity and possibly permeability played a role in ore formation however sulfides are also commonly orientated along but not deformed by a tectonic fabric or hosted within small fractures that suggest a significant role for deformation in the development of the mineralization the ore mineralogy hydrothermal alteration and stable isotope data lend support to models consistent with the thermochemical reduction of a sulfate and metal enriched hydrothermal fluid at the site of mineralization there is no evidence at nchanga for a contribution of bacteriogenic sulfide produced during sedimentation or early diagenesis to the ores

wave emplaced coarse debris and megaclasts in ireland and scotland boulder transport in a high energy littoral environment abstract many coastlines of the world particularly those at higher latitudes and those located in tropical cyclone belts are regularly battered by strong storm waves drowning of low lying areas by storm surges and storm floods has been thoroughly recorded however storm deposits at rocky shorelines or on cliffs have been underrepresented in the literature this article presents observations of extraordinary wave deposits along the high wave energy coastlines of western ireland and the northern scottish isles and discusses possible wave event types and time windows of the processes responsible we used archaeological geomorphological and geochronological disciplines to compare our findings with earlier results published for these areas and to contribute to the debate on whether large clasts found well above sea level and or a considerable distance inland were deposited by storms or by tsunamis

discrimination of boulders deposited by tsunamis and storm waves at ishigaki island japan abstract the ryukyu islands japan where numerous boulders are deposited on the reef and on land might be ideal research fields of boulders deposited by tsunami and storm waves because many typhoons and several tsunamis attacked the same area during its history this study investigates the size position and the long axis orientation of 626 boulders at ibaruma and shiraho reefs at ishigaki island japan to elucidate the sedimentary differences of boulders deposited by tsunamis and storm waves in one area two distinct groups of boulders were found at these reefs boulders on the reef crest group 1 and along the shoreline group 2 boulders in group 1 porites sp of moat origin the group 2 boulders were remarkably heavier 14 c age based on results of this study we infer that tsunami boulders in these islands so called tsunami ishi can be discriminated from boulders of storm wave origin based on their sedimentary differences this sedimentological approach is expected to be applicable to other boulder fields throughout the world our results further suggest that the spatial and grain size distribution of tsunami boulders are very useful to elucidate local flow characteristics of the tsunami for example the group 2 tsunami boulders were deposited below the high tide line irrespective of size some were split into several pieces they were probably deposited below the high tide line by the remarkable reduction of the current velocity of the tsunami because of the local topography the reduction of the current velocity must have been drastic to have made the boulders hit the ground with sufficient force to split them

wave emplaced coarse debris and megaclasts in ireland and scotland boulder transport in a high energy littoral environment a discussion scheffers et al 2009 describe a reconnaissance survey of boulder accumulations along parts of the atlantic coasts of the british isles a substantial part of their report concerns the characteristics of wave transported boulder deposits found high above sea level on cliffs these boulder deposits reach perhaps their ultimate development along the coasts of the aran islands galway bay western ireland and eshaness shetland northern scotland where evidence of wave action reaches elevations of 50 m above sea level a s l we have previously investigated in detail these and numerous other similar localities and concluded that the boulder deposits are cliff top storm deposits ctsds part of an assemblage of features found on certain cliffs on these very high energy coasts that relate to the impacts of extreme waves during major storms williams and hall 2004 hall et al 2006 2008 hansom et al 2008 hansom and hall 2009 however scheffers et al 2009 p 571 claim that at these and other sites no evidence exists for storm wave dislocation of boulders found at altitudes of 120 m a s l indeed no calculations of possible storm wave heights storm wave physics or ages of the deposits and no descriptions of extraordinary storms are sufficient to explain these displacements p 568 and alternative explanations such as tsunamis should be considered p 571 here we rebut these claims by briefly restat

alteration and ore distribution in the proterozoic mines series tenke fungurume cu co district democratic republic of congo two sediment hosted stratiform cu co deposits in the tenke fungurume district of the central african copperbelt were examined to evaluate the alteration history of the ore hosting mines series and its implications for ore distribution and processing core logging and petrography focused on lithology and timing relationships outlined a complex alteration sequence whose earliest features include formation of anhydrite nodules and laths followed by precipitation of dolomite later alteration episodes include at least two silica introductions accompanied by or alternating with two dolomite introductions into the existing gangue assemblages one introduction of cu co sulfides accompanied the last episode of dolomite alteration overprinting an earlier generation of ore whose gangue association was unidentifiable sulfides and some carbonates were subsequently modified by supergene oxidation transport and reprecipitation to 100 200 m depth present day ore distribution resulted from these successive processes ore is concentrated in two shale dominated units on either side of a cavernous silicified dolomite which is interpreted as the main conduit for the mineralizing fluids sulfide ores precipitated at the redox or sulfidation contacts between this dolomite and the shales later supergene fluids dissolved and moved some of the metals redepositing them as oxides and carbonates solubility differences between cu and co in supergene conditions caused them to precipitate separately thus modern ore distribution at tenke fungurume results both from original hypogene lithology and contact related precipitation and from supergene oxidation transport and cu co decoupling the supergene fluid flow also redistributed gangue minerals such as dolomite which has an economically important influence on the processing costs of supergene ores

neoproterozoic allochthonous salt tectonics during the lufilian orogeny in the katangan copperbelt central africa the neoproterozoic katangan rocks in the copperbelt of shaba democratic republic of the congo and zambia contain the world s largest concentration of stratiform copper cobalt ores we propose that during the lufilian orogeny the katangan basin was radically transformed first by extrusion of allochthonous evaporites then by orogenic shortening salt tectonics plausibly explains spectacular breccias underlying 25 000 km2 and containing gigaclasts up to 10 km long the brecciated shaban roan supergroup the lowermost katangan unit forms regional detachments and diapirs the former existence of roan evaporites is indicated by sabkha facies crystals and pseudomorphs of gypsum and anhydrite stratigraphic gaps underlain by collapse breccias chloride inclusions in ores hydrothermally propylitized ore hosts and saline springs salt tectonics began during deposition of the roan supergroup between 1050 and 950 ma in mid roan time small walls and extrusions of evaporite gigabreccia began to be emplaced in early kundelungu time 940 850 ma evaporitic diapirs enlarged lufilian deformation began between 850 and 650 ma by laterally squeezing diapirs to form salt welds then a large sheet of commingled roan evaporite and carbonate dominated sediments and ores was extruded northward by 65 km extrusion was fast enough to blanket a uniform preorogenic footwall unit without overriding any synorogenic deposits continued shortening then emplaced large thrust sheets lubricated by the preexisting salt sediment extrusive sheet restoration suggests that the lufilian foreland in this area shortened from 193 km to 85 km the depositional northern edge of the evaporite basin controlled the shape of the outer lufilian arc we infer three original salt provinces the large scale salt tectonics inferred here has implications for ore genesis and may yet be recognized in other precambrian basins

waves coastal boulder deposits and the importance of the pre transport setting the pre transport environment of a coastal boulder along with its shape size and density determines the height of wave required for it to be transported different forces act on sub aerial boulders as opposed to submerged boulders when struck by a wave boulders derived from joint bounded blocks on shore platforms predominantly experience lift force and require a wave of greater height to be transported than boulders in other environments no one equation is applicable to determine the height of palaeo waves responsible for depositing a field or ridge of imbricated coastal boulders a range of equations and their derivation is presented here which can be applied to the respective pre transport environment of a boulder such an approach is necessary when attempting to reconstruct the frequency and magnitude of past coastal wave hazards and for differentiating between tsunami and storm wave deposited boulder fields

surf zone transformation of wave height to water depth ratios abstract a solid body of data exists on which to base engineering decisions regarding the maximum wave heights that can be achieved in shallow water at the point of incipient breaking effort is now being directed towards the study of how wave height varies as waves propagate through the surf zone and what parameters control this process early surf zone models assumed a constant value of c while later models incorporate a decay function for h h due to turbulence in the breaking wave a few more recent studies have recognised a second process by which h h can decay through the surf zone where there is a strong underlying infragravity wave motion the work presented here investigates the characteristics of this latter decay process on a natural exposed dissipative beach including its magnitude and dual dependence on local mean water depth and distance from the breaker line some comparisons are then made with the decay characteristics of the former process

continental crustals regimes as factors in the formation of sedimentary ore deposits although the formation of metalliferous mineral deposits by processes active in sedimentary basins depends ultimately on physical and chemical conditions at the site of deposition the style scale and timing of mineralization are influenced by tectonic and magmatic events which relate to the evolution of the crustal environment as a whole during the archaean era when geothermal gradients were high and igneous activity widespread sedimentary processes played little part in mineralization the development of cratonic crustal massifs at the beginning of the proterozoic era was followed by an increase in the variety and size of deposits formed in sedimentary basins from this time onward the cratonic cover formations have provided important sites for the deposition of metals these metals entered the basins from a variety of sources some being derived from weathering and erosion of the basement and others being transferred to surface levels by magmas and volatiles originating in the mantle or lower crust it is suggested that the timing of mineralization is related to that of the major magmatic and tectonic happenings determined by the global tectonic regime

distribution geomorphology and lithofacies of cliff top storm deposits examples from the high energy coasts of scotland and ireland abstract cliff top storm deposits ctsds occur on cliffs at elevations of up to 50 m above sea level at exposed sites on the deep water coasts of the british isles this study examines the distribution geomorphology and lithofacies of ctsds at sites from shetland orkney caithness and the outer hebrides in scotland and from the aran islands in galway bay in ireland ctsds are generated largely by the quarrying of blocks from the cliff top and transported by green water bores across cliff top platforms and ramps to be deposited in backing ridges or as debris spreads maximum boulder sizes reach 48 m 3 but it is likely that much larger blocks can be quarried prior to disintegration during transport eye witness accounts and field mapping demonstrate that formation and modification of ctsds has continued during major storms over recent decades recent ctsds bury a range of man made debris but older deposits lack this and instead show weathering effects that indicate a longer residence time in shetland osl dates on intercalated sands suggest that the oldest ctsds date from 800 ad radiocarbon dates on shell buried inside ctsd ridges relate to major storms between 1700 and 1900 ctsds represent an overlooked archive of storm sedimentation that has great potential for the elucidation of local storm chronologies ctsds also provide evidence of wave impacts on any part of the cliff face or top in fundamental contrast to the concentration of wave action at the cliff foot implicit in traditional models of the erosion of rock coasts

a metamorphosed proterozoic carbonaceous shale hosted co ni cu deposit at kalumbila kabompo dome the copperbelt ore shale in northwestern zambia the kalumbila co ni cu prospect 12 15 s 25 20 e is located 300 km west of the zambian copperbelt on the southeastern flank of the kabompo dome in the middle unit of the lufilian arc kalumbila contains a drill indicated resource of 3 04 mt at 0 67 wt percent ni 0 2 wt percent co and 0 11 wt percent cu using a 0 08 wt percent co and 0 3 wt percent ni cutoff with an average thickness of 12 75 m ni co cu mineralization occurs as strata bound disseminated to finely laminated locally semimassive to locally discordant chalcopyrite pyrrhotite violarite and siegenite within a finely laminated highly carbonaceous and pyritic metapelite 300 500 m thick surface rock exposure in this low relief terrain of woodland and seasonal swamp is 1 percent and geophysics magnetic and electromagnetic surveys is an essential exploration tool detrital zircons in the kalumbila metasediments shrimp u pb ages of 2004 1884 ma are derived from the underlying paleoproterozoic granitic gneiss such as that exposed in the adjacent kabompo basement dome the metasedimentary sequence grades upward from siliciclastic rocks mica schists to the carbonaceous metapelite which hosts the co ni cu these units are overlain by dolomitic and mg rich schists possible meta evaporites which are in turn succeeded by calc silicate rocks and a deformed diamictite this sequence is broadly similar to the stratigraphy in the zambian copperbelt and suggests that the kalumbila carbonaceous metapelite may be the chronostratigraphic equivalent of the katangan roan ore shale a significant exploration target kalumbila occurs within a moderately 40 north northwest dipping band of wamikumbi formation carbonaceous metapelite on the flank of a recumbent south southeast verging f1 or f2 back fold during the lufilian orogeny peak metamorphic conditions at f1 were of amphibolite facies grade 650 c 13 kbars both monazites and rutiles within the kalumbila metasediments have metamorphic characteristics and late orogenic lufilian shrimp u pb ages 548 6 7 6 ma and 531 21 ma respectively sulfides in the metasediments display metamorphic textures and therefore predate the peak of lufilian tectonism and thermal metamorphism a suite of spatially associated apparently late lufilian gabbros intrude the metasedimentary rocks these gabbros are unmineralized but the thermal effects of their emplacement may have modified ore distribution a genetic model in which synsedimentary pyrite in a carbonaceous pelite was partially replaced by syndiagenetic or metamorphic co ni cu bearing fluids of unknown origin is favored

cobalt in the zambian copperbelt abstract a review of available information concerning the regional distribution of cobalt in the zambian copperbelt is presented which emphasises the limitation of this metal to a narrow possibly tectonically controlled zone on the southwestern flanks of the kafue anticline the stratigraphic location of cobalt bearing mineralisation is also examined though the majority of the known deposits are within the ore shale horizon cobalt has been found from the basement lower roan unconformity to the top of the lower roan and in one case high in upper roan dolomites the behaviour of cobalt relative to copper can best be summarised by considering arenite hosted deposits separately from those in the ore shale it is shown that though the latter appear to contain cobalt within the confines of the copper orebody a marked vertical antipathetic relationship exists the arenite hosted deposits on the other hand tend to display a marked lateral differentiation of the metals in that the cobalt has apparently migrated or been precipitated at or beyond the fringes of the copper orebody compositional variations within the cobalt bearing phases are described which are attributed to corresponding variations in host rock lithology primary porosity the availability of sedimentary or diagenetic sulphate and in particular to the activity of reduced sulphur a genetic model is thus presented which envisages influx of hot hydrothermal solutions into sediments during early diagenesis cooling of these solutions by mixing with connate waters together with the differing solubilities of the various metals results in the precipitation of the metals in a zonal fashion variable bacterial and possibly inorganic reduction of interstitial sulphate and consumption of the reduced sulphur controls not only the quantity but also the composition of the sulphides precipitated in the past the original source of the metals now contained in the orebodies has been dismissed as somewhat irrelevant but generally they were seen as having been derived from erosion of the basement granites or contained mineralisation a case is made that such a source is not compatible with the presence of high cobalt concentrations and that derivation from a differentiated basic magma is a more satisfactory explanation of the facts crustal rifting is the required mechanism for high level penetration of metal enriched hydrothermal fluids

sulfide bearing veinlets throughout the stratiform mineralization of the central african copperbelt temporal and genetic implications the central african copperbelt of zambia and democratic republic of congo along with its broad time equivalents in botswana and namibia the kalahari copperbelt is the world s largest sediment hosted stratiform copper province the economically dominant stratiform copper cobalt or silver mineralization accepted by many as at least partly early diagenetic in origin is ubiquitously accompanied by sulfide bearing quartz carbonate veins and veinlets traditionally this veining is considered to be the product of either metamorphic lateral secretion or discrete late diagenetic to synorogenic mineralization events this view is challenged because identical sulfide assemblages and textures characterize both the disseminated and accompanying veinlet mineralization throughout the zoned sulfide assemblages that constitute many of the stratiform orebodies a situation that is taken to imply contemporaneity of the two styles consequently during the mineralization the siltstone sandstone or dolomite host rocks must have been sufficiently competent to undergo widespread brittle fracturing implying that the disseminated mineralization cannot have been introduced by passive fluid infiltration during early diagenesis this conclusion is further supported by the local occurrence of minor disseminated and veinlet mineralization hosted by mafic sills and dikes both the disseminated and veinlet mineralization styles lack ductile deformation features in many congolese deposits but are variably metamorphosed and deformed in some deposits in zambia botswana and namibia in conjunction these observations suggest that the stratiform copper orebodies were the results of massive saline fluid expulsion by hydraulic fracturing after the mafic magmatism 765 715 ma most probably spanning peak damara lufilian metamorphism and ductile deformation 530 ma and continuing in places until at least 500 ma thus basin inversion contractional tectonism and associated uplift and exhumation and not the earlier extension and rifting seem more likely to have been the ultimate drivers for the fluid mobilization and expulsion

a numerical model for the transport of a boulder by tsunami 1 we have conducted hydraulic experiments in an open channel with cubic and rectangular shaped solid blocks on the slope for investigating the boulder transport process by tsunami in our experiments the block was mainly seen to be transported by a bore due to rolling or saltation rather than by sliding previous models for the boulder transport by tsunamis assumed sliding as a mode of transport for the boulder therefore these models underestimated the distance of the boulder moved by the tsunami when it was transported due to rolling or saltation in this study we have developed a practical model for the transport of a boulder by tsunami which takes into account the various transport modes we introduce an empirical variable coefficient of friction by assuming that the coefficient decreases with decrease in ground contact time when the block was transported by rolling or saltation with the aid of this parameter the model can explain various modes of transport i e sliding rolling and saltation and reproduces the experimental results well we further applied this improved model to a tsunami boulder at inoda area in ishigaki island japan which was transported by the 1771 meiwa tsunami the calculated distance of transport of the boulder was approximately 650 m which is consistent with the description in the historical document based on our calculations we estimated hydraulic values of the tsunamis estimation of such hydraulic values is important for understanding the behavior and power of the historical tsunamis besides aiding future disaster mitigation efforts

boulder accumulations related to storms on the south coast of the reykjanes peninsula iceland coastal boulder accumulations are often mentioned in the literature even though their interpretation remains difficult especially along rock coasts affected both by storms and tsunamis studies on the geomorphic impact of such high energy events are actually of great interest since their intensity and frequency are key issues for the future evolution of coasts in the framework of the global change the southwest coast of iceland faces the powerful storms of the north atlantic ocean with wave heights of more than 15 m the probability for past and present tsunamis to hit this coast is very low in this paper we describe boulder accumulations along the volcanic rock coast of reykjanes southwest iceland they consist of cliff top boulders clusters and ridges beaches and boulder fields large boulders up to 70 t in weight have been transported and deposited up to 65 m inland 6 masl the maximum limit of boulder deposition and driftwood was found respectively 210 m and 550 m inland storms appear to be a predominant factor in the geomorphic evolution of reykjanes coasts our observations also give new insight for the interpretation of coastal boulder accumulations processes of erosion and deposition by tsunamis are a rising topic in the literature and the effects of recurrent and powerful storms are neglected

genesis of the ores of the zambian copperbelt abstract the theories for the origin of the ores of the copperbelt of zambia and zaire are reviewed following an account of the historical development of ideas from epigenetic through syngenetic to syngenetic diagenetic and ultimately to neohydrothermalist theories models for the genesis of these deposits are critically assessed in the light of the data currently available this examination is conducted with particular regard to the questions of the sources of copper and cobalt the timing of mineralizing events and the physicochemical conditions of metal sulphide precipitation although accepting that the origin of these ores remains controversial it is concluded that the most likely sources of both copper and cobalt are the rocks of the basement complex that metals were probably transported both in surface and ground waters and that the main mineralizing event took place during early diagenesis with sulphide precipitation occurring via bacterial reduction of seawater sulphate the precipitation of sulphides probably occurred at temperatures around 20 60 c and at near neutral ph with minor fluctuations in eh and variations in the solubilities of the metals involved causing mineral zonation the burial and compaction of these sediments probably resulted in the expulsion of metal rich fluids and formation of sulphides in the immediate footwall and hanging wall of the main ore horizon with continued burial resulting in the formation of sulphide bearing pods and veins of lateral secretion origin tectonic deformation and metamorphism in the lufilian orogeny although resulting in a set of cross cutting high temperature mineralized veins appears not to have resulted in significant remobilization of the sulphides