the frequency and distribution of recent landslides in three montane tropical regions of puerto rico landslides are common in steep mountainous areas of puerto rico where mean annual rainfall and the frequency of intense storms are high each year landslides cause extensive damage to property and occasionally result in loss of life average population density is high 422 people km2 and is increasing this increase in population density is accompanied by growing stress on the natural environment and physical infrastructure as a result human populations are more vulnerable to landslide hazards the blanco cibuco and coamo study areas range in surface area from 276 to 350 km2 and represent the climatologic geographic and geologic conditions that typify puerto rico maps of recent landslides developed from 1 20 000 scale aerial photographs in combination with a computerized geographic information system were used to evaluate the frequency and distribution of shallow landslides in these areas several types of landslides were documented rainfall triggered debris flows shallow soil slips and slumps were most abundant hillslopes in the study area that have been anthropogenically modified exceed 12 in gradient are greater than 300 m in elevation and face the east northeast are most prone to landsliding a set of simplified matrices representing geographic conditions in the three study areas was developed and provides a basis for the estimation of the spatial controls on the frequency of landslides in puerto rico this approach is an example of an analysis of the frequency of landslides that is computationally simple and therefore may be easily transferable to other settings

cretaceous alkaline intra plate magmatism in the ecuadorian oriente basin geochemical geochronological and tectonic evidence abstract small volumes of cretaceous alkaline basaltic magmas have been identified in the sedimentary infill of the ecuadorian oriente foreland basin they are characterized by a restricted range of compositional variation low lile hfse ratios and sr nd isotope values within the range of oceanic island basalts oib reflection seismic data show that a pre existing nne ssw triassic and jurassic rift controls the location and occurrence of these alkaline eruptive sites radiometric ages 40ar 39ar incremental heating method and the biostratigraphic record of their surrounding sediments indicate a nne ssw systematic age variation for the emplacement of this alkaline volcanism from albian 110 5 2 ma in the northern part of the oriente basin to campanian 82 2 2 0 ma in the west central part the geochemical geochronological and tectonic evidences suggest that asthenospheric mantle has upwelled and migrated to the ssw into the region underlying the pre existing triassic and jurassic rift thin spot we propose that subduction was abandoned subsequent to the accretion of allochthonous terranes onto the ecuadorian and colombian margin in the latest jurassic earliest cretaceous causing the relict slab material corresponding to the eastwards directed leading plate to roll back unmodified asthenospheric mantle migrated into the region previously occupied by the slab this resulted in partial melting and the release of magmatic material to the surface in the northern part of the oriente basin since at least aptian times then magmatism migrated along the ssw trending central wrench corridor of the oriente basin during the upper cretaceous probably as a consequence of the lateral propagation of the transpressive inversion of the triassic jurassic rift eventually the late cretaceous east dipping andean subduction system was renewed farther west and the development of the compressional retro foreland oriente basin system halted the cretaceous alkaline magmatic activity

comparison of the implementation of rock engineering system and analytic hierarchy process methods upon landslide susceptibility mapping using gis a case study from the eastern achaia county of peloponnesus greece as landslides are very common in greece causing serious problems to the social and economic welfare of many communities the implementation of a proper hazard analysis system will help the creation of a reliable susceptibility map his will help local communities to define a safe land use and urban development the purpose of this study is to compare the implementation of two semi quantitative landslide assessment approaches using landslide susceptibility maps compiled in a gis environment the compared methods are rock engineering system res and the analytic hierarchy process ahp for the landslide susceptibility analysis the northeastern part of the achaia county was examined this area suffers from many landslides because of its neighborhood with the tectonically active corinthian gulf and its geological setting neogene sediments flysch and other bedrock formations with local overthrusts ten parameters were used in both methodologies and each one was separated into five categories ranging from 0 to 4 representing their specific conditions derived from the investigation of the landslides in the western part of the study area ranking area a layer map was generated for each parameter using gis while the weighting coefficients of each methodology were used for the compilation of res and ahp final maps of the eastern part of the study area validating area by examining these two maps it is revealed that even though both correctly show the landslide status of the second site the res map reveals a better behavior in the spatial distribution of the various landslide susceptibility zones

origin and cretaceous tectonic history of the coastal ecuadorian forearc between 1 n and 3 s paleomagnetic radiometric and fossil evidence the presence of at least one block pallatanga block derived from the caribbean colombian oceanic plateau has been proposed in the western cordillera of ecuador new 40ar 39ar dating of the basement of the coastal blocks 90 87 ma and fossil ages in the overlying calentura fm 89 84 ma argue for late turonian coniacian extrusion of the basement of the pinon block paleomagnetic inclinations indicate that the mafic basement of the pinon and san lorenzo blocks extruded at equatorial low southern latitudes no subsequent significant latitudinal drift can be observed during the cretaceous rapid changes in paleomagnetic declination between 73 and 70 ma in both the pinon and the san lorenzo blocks indicate that the large igneous province which originally hosted the coastal blocks experienced a major tectonic event during late campanian times similar late turonian coniacian basement ages and late campanian tectonic events are reported in the pallatanga block of the western cordillera we propose that the pinon san lorenzo and pallatanga blocks all derive from a common large igneous province the caribbean colombian oceanic plateau and were incorporated into the south american margin by collision during the late campanian 73 70 ma

cretaceous early paleocene drainage shift of amazonian rivers driven by equatorial atlantic ocean opening and andean uplift as deduced from the provenance of northern peruvian sedimentary rocks huallaga basin abstract the northern part of south america has undergone several major changes in its tectonic setting since the triassic evolving from rifting to the development of a retroarc foreland basin on its andean margin leading to margin extension and continental uplift following the breakup between africa and south america so far it is unclear when and how these geodynamic events affected the paleo amazonian drainage in this study we investigate the provenance of triassic eocene sedimentary rocks deposited in the northern peruvian amazonian basin based on their sr nd isotopic compositions and u pb zircon dating the triassic jurassic samples have end 0 values ranging from 7 9 to 10 0 and main u pb zircon peaks at 0 9 1 3 ga 31 33 and 0 5 0 7 ga 21 28 that suggest a mixed clastic supply from the western and eastern cordillera or craton within a rift to post rift setting samples from the albian maastrichtian interval yield much lower end 0 values 16 8 to 18 6 and a dominance of zircon grains derived from terranes in the easternmost brazilian shield ventuari tapajos 2 0 1 82 ga rio negro jurena 1 82 1 54 ga and rondonia san ignacio 1 54 1 3 ga thus indicating a cratonic source for these sedimentary rocks finally the early paleocene eocene sedimentary rocks record the first arrival of andean detritus in the amazonian retroarc foreland with end 0 values ranging between 5 6 to 12 0 and up to 16 of the zircon grains yielding ages younger than 120 ma together with recently published studies these provenance data document the existence of a long lived aptian maastrichtian continent wide cratonic drainage in the northern part of south america this cratonic drainage developed in response to the late cretaceous uplift of the northeastern part of the south america craton likely driven by geodynamic processes related to post rift opening of the atlantic equatorial ocean the formation of a late maastrichtian early paleocene mountain chain in the peruvian andes associated with the onset of provenance from the andean orogenic belt led to a shift of the amazon drainage pattern hence the earliest andean amazonian rivers are no younger than late maastrichtian early paleocene

petroleum generation and migration in the putumayo basin colombia insights from an organic geochemistry and basin modeling study in the foothills this paper discusses the results of 1d modeling and geochemical analyses of rock oil and gas samples performed in the foothills of the putumayo basin colombia a multivariate statistical assessment of biomarker data points to the existence of three oil groups two of the them similar to oil families reported in previous studies and related to the villeta formation source rocks and a novel one tentatively associated with the caballos formation source rocks geochemical data of oil and gas samples points to a complex reservoir filling history in the foothills with at least two migration pulses with distinct maturity levels vitrinite reflectance data together with modeling results shows that the source rock is practically immature in the putumayo foothills even in the footwall of large thrust faults the thermal and burial reconstruction of a pseudo well located in the present cordillera area suggests that the source rocks have started petroleum generation and expulsion during the late oligocene miocene the oil and gas expelled during such a period have migrated over 80 km reaching the present foreland area subsequent tectonic burial and or higher heat flows related to the late miocene pliocene andean paroxysm is thought to account for a second pulse of migration of thermally evolved hydrocarbons limited to the foothills area

dynamics of fluvial and slope processes in the changing geomorphic environment of singapore the nature and rates of fluvial and slope processes change over time and space as urbanized areas replace forested land in singapore storm based and time based data from undisturbed rainforests heavily disturbed construction sites urban grass covered slopes and an experimental plot are collected to observe the impact of rainwater on the soil moisture conditions surface microtopography runoff generation sediment movement and ground lowering in the three different categories of land use the undisturbed forested environment is characterized by high throughfall 58 of total rainfall and frequent negative soil moisture suctions the slow and unconcentrated overland flow during heavy storms is restricted by the forest floor microtopography no rills develop ground lowering is recorded as 3 2 3 4 mm a 1 but sediment movement is episodic and suspended sediment concentrations in overland flow are 172 222 mg l 1 during urban construction gully development is rapid on the bare slopes runoff generation voluminous and sediment laden discharges 5200 75498 mg l 1 lead to sediment plumes at channel mouths ground lowering rates are measured at 132 4 mm a 1 once grass covered runoff carries less suspended sediment 800 mg l 1 and ground lowering rates are reduced but depend on the condition of the cover ranging from 0 2 to 8 2 mm a 1 as urban development continues environments are altered both in time as well as spatially

gis techniques and statistical models in evaluating landslide hazard geographical information systems gis and numerical cartography may greatly facilitate the development and use of statistical models for the assessment of regional landslide hazard from a small drainage basin located in central italy relevant geological and geomorphological factors were collected and processed by applying gis technology in particular modules were used which both generate high fidelity digital terrain models and automatically partition the terrain into main slope units the resulting information was then analysed by discriminant analysis which enabled landslide hazard and risk to be evaluated in each slope unit although not lacking drawbacks the method proved to be a feasible and cost effective approach to landslide susceptibility assessment and mapping

slopewash surface runoff and fine litter transport in forest and landslide scars in humid tropical steeplands luquillo experimental forest puerto rico rainfall slopewash the erosion of soil particles surface runoff and fine litter transport at humid tropical steepland sites in the luquillo experimental forest puerto rico 188 20 n 658 45 w were measured from 1991 to 1995 hillslopes underlain by 1 cretaceous tuffaceous sandstone and siltstone in subtropical rain tabonuco forest with vegetation recovering from hurricane hugo 1989 and 2 tertiary quartz diorite in subtropical lower montane wet colorado and dwarf forest with undisturbed forest canopy were compared to recent landslide scars monthly surface runoff on these very steep hillslopes 248 to 438 was only 0 2 to 0 5 per cent of monthly rainfall slopewash was higher in sandy loam soils whose parent material is quartz diorite averaging 46 g m 2 a 1 than in silty clay loam soils derived from tuffaceous sandstone and siltstone where the average was 9gm 2 a 1 annual slopewash of 100 to 349 gm 2 on the surfaces of two recent small landslide scars was measured initially but slopewash decreased to only 3 to 4 g m 2 a 1 by the end of the study the mean annual mass of fine litter mainly leaves and twigs transported downslope at the forested sites ranged from 5 to 8 g m 2 and was lower at the tabonuco forest site where post hurricane hugo recovery is still in progress mean annual fine litter transport was 2 5gm 2 on the two landslide scars copyright 1999 john wiley sons ltd

sequence stratigraphic controls on complex reservoir architecture of highstand fluvial dominated deltaic and lowstand valley fill deposits in the upper cretaceous cenomanian woodbine group east texas field regional and local perspectives an analysis of 31 whole cores 1600 ft 490 m and closely spaced wireline logs 500 wells penetrating the lower cretaceous cenomanian lower woodbine group in the mature east texas field and adjacent areas indicates that depositional origins and complexity of the sandstone body architecture in the field vary from those inferred from previous studies heterogeneity in the lower woodbine group is controlled by highstand fluvial dominated deltaic depositional architecture with dip elongate distributary channel sandstones pinching out over short distances typically 500 ft 150 m into delta plain and interdistributary bay siltstones and mudstones this highstand section is truncated in the north and west parts of the field by a thick maximum of 140 ft 43 m lowstand incised valley fill succession composed of multistoried coarse gravel conglomerate and coarse sandstone beds of bed load fluvial systems in some areas of the field this valley fill directly overlies distal delta front deposits recording a fall in relative sea level of at least 215 ft 65 m correlation with the woodbine succession in the east texas basin indicates that these highstand and lowstand deposits occur in the basal three fourth order sequences of the unit which comprises a maximum of 14 such cycles previous studies of the woodbine group have inferred meanderbelt sandstones flanked by coeval flood plain mudstones and well connected laterally continuous sheet sandstones of wave dominated deltaic and barrier strand plain settings this model is inappropriate and a full assessment of reservoir compartmentalization fluid flow and unswept mobile oil in east texas field should include the highstand fluvial dominated deltaic and lowstand valley fill sandstone body architecture

rainfall induced landslide susceptibility zonation of puerto rico landslides are a major geologic hazard with estimated tens of deaths and 1 2 billion in economic losses per year in the us alone the island of puerto rico experiences one or two large events per year often triggered in steeply sloped areas by prolonged and heavy rainfall identifying areas susceptible to landslides thus has great potential value for puerto rico and would allow better management of its territory landslide susceptibility zonation lsz procedures identify areas prone to failure based on the characteristics of past events lszs are here developed based on two widely applied methodologies bivariate frequency ratio fr method and logistic regression lr method with these methodologies the correlations among eight possible landslide inducing factors over the island have been investigated in detail both methodologies indicate aspect slope elevation geological discontinuities and geology as highly significant landslide inducing factors together with land cover for the fr method and distance from road for the lr method the lr method is grounded in rigorous statistical testing and model building but did not improve results over the simpler fr method accordingly the fr method has been selected to generate a landslide susceptibility map for puerto rico the landslide susceptibility predictions were tested against previous landslide analyses and other landslide inventories this independent evaluation demonstrated that the two methods are consistent with landslide susceptibility zonation from those earlier studies and showed this analysis to have resulted in a robust and verifiable landslide susceptibility zonation map for the whole island of puerto rico

migration of cenozoic deformation in the eastern cordillera of colombia interpreted from fission track results and structural relationships implications for petroleum systems previously unreleased fission track results and regional structural relationships are used to interpret the migration of deformation during cenozoic orogenesis in the eastern cordillera cordillera oriental of the colombian andes low temperature thermochronological results are based on apatite and zircon fission track analyses of 41 samples collected along vertical and horizontal transects across the eastern cordillera at 4 7n latitude inverse modeling of fission track results helps delimit the most probable cooling histories caused by exhumation linked to upper crustal deformation these inverse models are constrained by known structural geometries chronostratigraphy biostratigraphy and vitrinite reflectance data fission track data and modeling results indicate a close correspondence in the timing and style of deformation along the western and eastern flanks of the eastern cordillera east directed fold thrust deformation along the eastern boundary with the llanos foreland basin was underway by the late oligocene and early miocene similarly west directed fold thrust structures along the western boundary with the intermontane middle magdalena valley basin became active at approximately the same time less well known is the time of initial shortening within the axial segment of the eastern cordillera although fission track results suggest active exhumation by the early miocene shortening may have commenced much earlier during the late eocene timing relationships for the eastern cordillera have important implications for the generation migration and accumulation of petroleum in the middle magdalena valley intermontane basin and the llanos foreland basin our study provides a regional context to assess the timing of structural trap development and improve exploration and development of new and existing reservoirs in colombia and analogous fold thrust systems elsewhere

how wide is a road the association of roads and mass wasting in a forested montane environment a spatial data base of 1609 landslides was analysed using a geographic information system to determine landslide frequency in relation to highways a 126 km long transportation network in a 201km 2 area of humid tropical mountainous forested terrain in puerto rico was used in conjunction with a series of 20 buffer disturbance zones varying from 5 to 400 m in length measured perpendicular to the highways average landslide frequency in the study area at distances greater than 85 m from roads was about six landslides per square kilometre at distances of 85 m or less on either side of a highway landslide frequency was about 30 landslides per square kilometre on average this elevated disturbance rate affected 330 m 2 km 2 a 1 within the 170 m swath the mass wasting rate outside of the disturbance zone affected 40 m 2 km 2 a 1 these results indicate that the rate of mass wasting disturbance is increased from five to eight times in a 170 m wide swath along road corridors the lateral extent of the environmental impact of roads in the study area is greater than is commonly perceived the approach described herein demonstrates a simple method to assess the spatial association of mass wasting with highways 1997 by john wiley sons ltd

anatomy of collapsed and re established delta front in lower cretaceous of eastern spitsbergen gravitational sliding and sedimentation processes spectacular coastal cliff exposures in an early cretaceous deltaic succession near kvalvagen in eastern spitsbergen norwegian arctic show a variety of styles of gravity driven deformation and resedimentation associated with delta front progradation and instability the large scale collapse involved a distributary channel sand unit some 20 m thick and the underlying delta slope prodelta shaly heterolithics the deformation was essentially brittle whereby large blocks of the delta front succession slid and rotated its gross style involved two large cuspate tear away scars at least 1 1 5 km wide and 50 60 m deep separated by narrow remnant buttresses of in situ strata the basement in the region was tectonically active and the delta front failure was most likely sei mically triggered initial infill of the collapse scars involved slumps and debris flows derived from scar walls and locally from the sliding blocks themselves these deposits partly smoothed the local topography created by the slide blocks this early infill was followed by deposition of thin mainly muddy turbidites probably shed from the scar walls by small localized failure renewal of fluvial supply of sand led to the main infill of the scar depressions this stage involved effluent generated turbidites heterolithic and increasingly sandier turbidites and liquefied sandflows derived from unstable oversteepened distributary mouthbars the mouth bar systems eventually achieved stability and prograded across the infilled scars they were affected by periodic storm wave attack and sudden increa es of water depth the scar infill at that stage was subject to minor growth faulting possibly related to new seismic tremors

campanian miocene tectonostratigraphy depocenter evolution and basin development of colombia and western venezuela abstract the position of the central axis of deposition over colombian and venezuelan continental crust has varied markedly through time the axis migrated from west to east from late cretaceous to oligocene but at times secondary drainage divides were established by local uplift events in oligocene times with initial inversion of the eastern cordillera the central axis of deposition was divided into two main axes the proto magdalena and the proto orinoco systems the west to east migration of the central axis of deposition had a tectonic origin and it occurred in combination with tectonically driven changes in accommodation space depocenter evolution can be divided as follows 1 the axis of the campanian and early maastrichtian depocenter was located few km east of the present position of the central cordillera of colombia it migrated east with gradual uplift of the central cordillera 2 the central axis of late maastrichtian deposition is positioned approximately over the present day western foothills of the eastern cordillera possibly crosses the eastern cordillera over the santander massif and continues into the maracaibo lake in western venezuela accommodation space decreased from campanian to maastrichtian times in cretaceous tertiary boundary times parts of the eastern margin of the eastern cordillera were uplifted by an initial phase of inversion of deeply rooted jurassic and early cretaceous normal faults 3 in paleocene times the central axis of deposition was located along the spine of the eastern cordillera and extended into the maracaibo basin and accommodation space continued to decrease 4 in latest paleocene times the central axis of deposition shifted to eastern regions of the eastern cordillera and accommodation space decreased 5 the early eocene central axis of deposition was located along the present day eastern foothills of the eastern cordillera accommodation space continued to decrease and the regional middle eocene unconformity began to develop in middle eocene times a regional unconformity developed marking the climax of the pre andean orogeny deposition during these times was dominant in the maracaibo basin area where large amounts of sediment derived from vast exposed areas accumulated 6 the late eocene central axis of deposition was confined to the present position of the llanos foothills late eocene deposition reflects a regional increase in accommodation space in oligocene times the initial uplift of the eastern cordillera divided the main depocenter into two central axes accommodation space diminished in uplifted regions but continued to increase in the depocenters allowing sporadic marine ingressions into the present position of the llanos foothills as uplift of the eastern cordillera continued the eastern depocenter axis proto orinoco migrated east and the western depocenter axis proto magdalena migrated west this process continued through the rest of the cenozoic

measurement and prediction of sediment production from unpaved roads st john us virgin islands excess delivery of land based sediments is an important control on the overall condition of nearshore coral reef ecosystems unpaved roads have been identified as a dominant sediment source on st john in the us virgin islands an improved understanding of road sediment production rates is needed to guide future development and erosion control efforts the main objectives of this study were to 1 measure sediment production rates at the road segment scale 2 evaluate the importance of precipitation slope contributing area traffic and grading on road sediment production 3 develop an empirical road erosion predictive model and 4 compare our measured erosion rates to other published data sediment production from 21 road segments was monitored with sediment traps from july 1998 to november 2001 the selected road segments had varying slopes contributing areas and traffic loads precipitation was measured by four recording rain gauges sediment production was related to total precipitation and road segment slope after normalizing by precipitation and slope the mean sediment production rate for roads that had been graded within the last two years was 0 96 kg m 2 cm 1 m m 1 or approximately 11 kg m 2 a 1 for a typical road with a 10 per cent slope and an annual rainfall of 115 cm a 1 the mean erosion rate for ungraded roads was 42 per cent lower or 0 56 kg m 2 cm 1 m m 1 the normalized mean sediment production rate for road segments that had been abandoned for over fifteen years was only about 10 per cent of the mean value for ungraded roads sediment production was not related to traffic loads multiple regression analysis led to the development of an empirical model based on precipitation slope to the 1 5 power and a categorical grading variable the measured and predicted erosion rates indicate that roads are capable of increasing hillslope scale sediment production rates by up to four orders of magnitude relative to undisturbed conditions the values from st john are at the high end of reported road erosion rates a finding that is consistent with the high rainfall erosivities and steep slopes of many of the unpaved roads on st john other than paving the most practical methods to reduce current erosion rates are to minimize the frequency of grading and improve road drainage copyright 2005 john wiley sons ltd

structural and hydrogeologic evolution of the putumayo basin and adjacent fold thrust belt colombia this multidisciplinary study evaluates the structural and hydrogeologic evolution of cretaceous age reservoirs in the putumayo basin colombia we focused on the eastern cordillera fold thrust belt along the southern garzon massif many important hydrocarbon accumulations occurred regionally along the proximal foreland basin and frontal fold thrust belt defining the eastern margin of the northern andes to understand why recent putumayo basin and adjacent thrust belt exploration has resulted in a wide range of oil quality and limited economic discoveries we reconstructed the structural evolution timing of oil migration and timing of groundwater infiltration by 1 assessing regional trends in formation water oil and reservoir properties 2 quantifying the timing of hydrocarbon generation and migration relative to trap formation using a two dimensional 2 d and three dimensional seismic data to define and constrain a restorable balanced cross section from the upper magdalena valley to the putumayo foreland and b coupled one dimensional thermal basin modeling 3 evaluating the potential roles of mesozoic extensional faulting and paleogene shortening in the generation and preservation of structural traps and 4 assessing groundwater influx from the modern foothills into the reservoir using a 2 d numerical groundwater flow model we suggest that four way closure is limited in the study area where most foreland verging structures create three way fault closures that do not effectively trap light hydrocarbons in addition east dipping structures and a relatively large reservoir outcrop area provide water infiltration pathways groundwater modeling suggests reservoirs were water washed by 2 200 million pore volumes since andean uplift finally average reservoir temperatures are 80 c 176 f which further facilitated biodegradation

measurement and prediction of natural and anthropogenic sediment sources st john u s virgin islands abstract a quantitative understanding of both natural and anthropogenic sediment sources is needed to accurately assess and predict the potentially adverse effects of land development on aquatic ecosystems the main objective of this study was to quantify sediment production and delivery rates in a dry tropical environment on the island of st john in the eastern caribbean one to three years of measurements were used to determine values and empirical functions for estimating sediment production from streambanks treethrow undisturbed hillslopes zero order sub catchments unpaved road surfaces and road cutslopes sediment production also was measured from both undisturbed and roaded first order sub catchments among natural sources of sediment streambanks had the highest mean erosion rate at 100 mg ha 1 yr 1 the uprooting of trees along stream margins is estimated to generate approximately of 0 2 mg of sediment per kilometer of stream per year or about 0 1 mg ha 1 yr 1 for a stream corridor that consists of a 9 m wide channel and a 3 m wide buffer zone undisturbed 40 m 2 hillslope plots generated 0 01 to 0 27 mg ha 1 yr 1 mean sediment yields from undisturbed zero and first order catchments were only 0 01 and 0 08 mg ha 1 yr 1 respectively unpaved roads that were graded at least every other year had sediment production rates ranging from 57 mg ha 1 yr 1 for a road with a 2 slope to 580 mg ha 1 yr 1 for a road with a 21 slope sediment production rates from ungraded roads were about 40 lower than those from recently graded roads while production rates from steep abandoned roads were only 12 mg ha 1 yr 1 cutslope sediment production rates ranged from 20 to 170 mg ha 1 yr 1 but their contribution to sediment yields at the road segment scale was relatively small since unpaved roads increase hillslope scale sediment production rates by several orders of magnitude the first order catchments with unpaved roads had sediment yields that were at least five times higher than undisturbed catchments the relative importance of each sediment source varies from catchment to catchment as a result of the abundance and spatial distribution of landscape types the values and predictive functions developed in this study have been incorporated into a gis based model to predict catchment scale sediment yields application of this model to three basins in st john suggest that unpaved roads are currently the dominant sediment source and that they are responsible for increasing watershed scale sediment yields by 3 9 times relative to undisturbed conditions both the data from the present study and the gis model can help estimate sediment production and catchment scale sediment yields in similar environments

numerical models of translational landslide rupture surface growth we analyze the initiation and enlargement of the rupture surface of translational landslides as a fracture phenomenon using a two dimensional boundary element method both processes are governed largely by the stress field and the pre existing planes of weakness in a slope near the ground surface the most compressive stress becomes either parallel or perpendicular to the slope depending on the topography and regional stresses the shear stress available to drive slope parallel sliding in a uniform slope thus is small and therefore pre existing weaknesses are required in many cases for sliding stresses in a uniform slope favor the initiation of sliding near the slope base sliding can progress upslope from there in retrogressive fashion most slopes are not uniform and notches in a slope will concentrate stresses and generally promote sliding there as the region of sliding at depth enlarges the stress concentration near the edge of the area of slip will tend to rise stress concentrations can become sufficient to open fractures above and below a basal slide plane in keeping with observations if one tip of a slide plane intersects the ground surface then stresses near the other tip can increase markedly as can slip our analyses show that slope parallel sliding along a plane at depth will cause downslope extension in the upslope half of a slide mass and shortening in the downslope half consistent with observations displacement profiles that could be interpreted as rotational can result from sliding along such a plane however careful analysis of surface deformation can be used to understand sliding at depth

basin development and tectonic history of the llanos basin eastern cordillera and middle magdalena valley colombia the middle magdalena valley eastern cordillera and llanos basin constituted a major regional sedimentary basin from the triassic to the middle miocene basin development began during the triassic to the earliest cretaceous with a synrift megasequence related to the separation of north and south america in the proto caribbean the synrift megasequence began with deposition in a continental environment that became paralic and shallow marine in the early cretaceous basin development continued into the cretaceous in a back arc setting east of the andean subduction zone the back arc megasequence was dominated by shallow marine sedimentation and produced an excellent regional source rock during the turonian coniacian marine deposition was abruptly terminated during the ear y maastrichtian due to the final accretion of the western cordillera accretion of the western cordillera created the early pre andean foreland basin megasequence of late maastrichtian to early eocene age this depositional episode consists of coal rich alluvial plain coastal plain and estuarine deposits throughout the middle magdalena valley eastern cordillera and eastern llanos basin the megasequence was terminated by middle eocene deformation in the magdalena valley which ended sediment deposition throughout colombia loading effects of this deformation reestablished the basin in which the late pre andean foreland basin megasequence was deposited until the early miocene this megasequence also consists of alluvial plain coastal plain and estuarine deposits including the primary reservoir in the llanos foothills the upper eocene mirador fo mation the megasequence also includes a series of four major grossly coarsening upward cycles in the llanos basin these cycles correspond to changes in sea level sediment supply and foreland basin loading the mudstone in the lowermost of these cycles is the regional seal in the llanos basin and foothills the middle miocene onset of andean deformation in the eastern cordillera isolated the middle magdalena valley from the llanos basin the deformation was dominated by inversion of the basin controlling faults the resultant loading of the lithosphere created the accommodation space for the andean foreland basin megasequence a major transgression into the llanos basin coeval with this deformation caused deposition of marine mudstones in the lower part of the megasequence however the majority of the andean foreland basin megasequence consists of the guayabo formation a classic molasse sequence deposited in a high energy coarse grained bed load dominated fluvial system that was supplied by the developing mountains of the eastern cordillera

spatial and temporal analysis of a global landslide catalog abstract landslide inventories are critical to support investigations of where and when landslides have happened and may occur in the future however there is surprisingly little information on the historical occurrence of landslides at the global scale this paper presents a new publicly available global landslide catalog glc which is based on media reports online databases and other sources this database is currently available at http ojo streamer herokuapp com the 5741 points in the glc provide a foundation for evaluating spatial and temporal trends in landslide activity from 2007 to 2013 globally landslides were reported most frequently from july to september most events occurred in asia north america and southeast asia in contrast fewer than 5 of the fatalities were reported in north america suggesting a significant amount of under reporting in other regions as well as potential discrepancies between developing and developed regions reported landslide events were also compared to satellite based precipitation estimates from the tropical rainfall measuring mission trmm to evaluate the co occurrence of extreme precipitation and landslide activity of the 3550 points considered in a subset of the glc approximately 60 of the reported landslides have daily precipitation exceeding the 95th percentile of precipitation calculated over a 14 year trmm record for the same location this study also investigated how the recurrence interval of extreme precipitation corresponded to some of the most catastrophic landslide events in spite of several reporting and cataloging biases spatial and temporal analysis of the glc suggests that it is a valuable database for characterizing global patterns of landslide occurrence and evaluating relationships with extreme precipitation at regional and global scales

landslide susceptibility mapping along road corridors in the indian himalayas using bayesian logistic regression models landslide susceptibility mapping lsm along road corridors in the indian himalayas is an essential exercise that helps planners and decision makers in determining the severity of probable slope failure areas logistic regression is commonly applied for this purpose as it is a robust and straightforward technique that is relatively easy to handle ordinary logistic regression as a data driven technique however does not allow inclusion of prior information this study presents bayesian logistic regression blr for landslide susceptibility assessment along road corridors the methodology is tested in a landslide prone area in the bhagirathi river valley in the indian himalayas parameter estimates from blr are compared with those obtained from ordinary logistic regression by means of iterative markov chain monte carlo simulation blr provides a rich set of results on parameter estimation we assessed model performance by the receiver operator characteristics curve analysis and validated the model using 50 of the landslide cells kept apart for testing and validation the study concludes that blr performs better in posterior parameter estimation in general and the uncertainty estimation in particular

andean trending mobile belts in the brazilian shield much of the phanerozoic andean mountain chain is floored by precambrian basement1 3 in places as old as 2 000 myr4 5 but relations between these rocks and those of the brazilian shield have long been obscure mainly because of the intervening cenozoic sedimentary cover we describe here recent work over the bolivian sector of the brazilian shield fig 1 which shows a pattern of proterozoic mobile belts approximately parallel with the andean chain to the west when the trends of these bolivian belts are projected towards the andes under the cenozoic cover their ages broadly accord with those of the andean basement our interpretation is that the two domains are linked in the form of a chain of five andean trending mobile belts with a combined width of 1 000 km becoming progressively younger to the west with ages ranging from 1 300 myr to the present

types of submarine fan lobes models and implications different lobe models imply significantly different reservoir geometries thus one must apply the proper lobe model to ancient fan sequences braided suprafan lobes are characterized by stacked channel sand bodies with good lateral and vertical communication and they constitute excellent reservoir facies depositional lobes composed of sheet like sand bodies with good lateral and moderate vertical communication exhibit properties of good reservoir facies fanlobes which refer to meandering channels and associated levee facies of large mud rich submarine fans such as the mississippi fan are characterized by offset stacked sand bodies with poor lateral and vertical communication these lenticular sands have the potential to be moderately good reservoir facies ponded obes which represent mud rich slump facies of slope environments comprise poor reservoir facies because of low sand content and poor sand body connectivity furthermore the presence of contorted mud layers in ponded lobes is expected to hinder fluid flow external mounded reflections in seismic profiles often are interpreted as lobes however there are no definite seismic criteria to delineate mud rich lobes from sand rich lobes

sacha oil field of ecuadorian oriente the sacha oil field in the ecuadorian oriente was discovered in early 1969 production began in july 1972 and at the end of 1980 had exceeded 190 million bbl drilling through 1980 had resulted in 91 oil wells and 2 dry holes estimated original primary recoverable reserves surpass 632 million bbl the field is on a very low relief anticline about 17 5 mi 28 km long and averaging 4 mi 6 5 km wide vertical closure amounts to 200 ft 60 m and there are 41 000 acres 16 600 ha of areal closure on top of the principal reservoir the cretaceous sandstones at drilled depths between 9 300 and 10 100 ft 2 835 and 3 080 m provide excellent reservoirs the hollin formation the basal cretaceous sandstone is the principal reservoir having produced 80 of the oil through 1980 and containing about 68 of the original reserves

human impacts to mountain streams mountain streams are here defined as channel networks within mountainous regions of the world this definition encompasses tremendous diversity of physical and biological conditions as well as history of land use human effects on mountain streams may result from activities undertaken within the stream channel that directly alter channel geometry the dynamics of water and sediment movement contaminants in the stream or aquatic and riparian communities examples include channelization construction of grade control structures or check dams removal of beavers and placer mining human effects can also result from activities within the watershed that indirectly affect streams by altering the movement of water sediment and contaminants into the channel deforestation cropping grazing land drainage and urbanization are among the land uses that indirectly alter stream processes an overview of the relative intensity of human impacts to mountain streams is provided by a table summarizing human effects on each of the major mountainous regions with respect to five categories flow regulation biotic integrity water pollution channel alteration and land use this table indicates that very few mountains have streams not at least moderately affected by land use the least affected mountainous regions are those at very high or very low latitudes although our scientific ignorance of conditions in low latitude mountains in particular means that streams in these mountains might be more altered than is widely recognized four case studies from northern sweden arctic region colorado front range semiarid temperate region swiss alps humid temperate region and papua new guinea humid tropics are also used to explore in detail the history and effects on rivers of human activities in mountainous regions the overview and case studies indicate that mountain streams must be managed with particular attention to upstream downstream connections hillslope channel connections process domains physical and ecological roles of disturbance and stream resilience

upper wilcox rosita delta system of south texas growth faulted shelf edge deltas the rosita delta system a heretofore unrecognized major depositional system preserved in the deep upper wilcox of south texas was delineated by detailed correlation of approximately 500 well logs the rosita delta system comprises at least three delta complexes each of which can be traced up to tens of miles along strike and up to approximately 15 mi 24 km downdip basinward across the growth fault zone each delta complex thickens from about 600 ft 180 m to more than 3 000 ft 900 m the growth faults were activated by progradation of deltas over unstable prodelta slope muds at the contemporary shelf margin the three upper wilcox delta complexes studied in detail are from oldest to youngest the duval zapata and live oak deltas named for the counties in which they are centered each complex consists of several lobes some of which can be traced across the deep zones where the thickness increases by as much as tenfold owing to progradation over active growth faults characteristic coarsening upward progradational units are interpreted from electric log patterns to include prodelta shales delta front sandstones distributary channel and channel mouth bar sandstones and interdistributary shales and sandstones appreciable variability in sandstone distribution in the deltas may reflect changing importance of fluvial versus marine currents in distributing sediment along the delta front however all of the deltas prograded abruptly toward the shelf margin the gulfward extent of these delta complexes is unknown and it is concluded that appreciable quantities of sandstone remain to be explored in the deep subsurface of the trend

the application of gis based logistic regression for landslide susceptibility mapping in the kakuda yahiko mountains central japan as a first step forward in regional hazard management multivariate statistical analysis in the form of logistic regression was used to produce a landslide susceptibility map in the kakuda yahiko mountains of central japan there are different methods to prepare landslide susceptibility maps the use of logistic regression in this study stemmed not only from the fact that this approach relaxes the strict assumptions required by other multivariate statistical methods but also to demonstrate that it can be combined with bivariate statistical analyses bsa to simplify the interpretation of the model obtained at the end in susceptibility mapping the use of logistic regression is to find the best fitting function to describe the relationship between the presence or absence of landslides dependent variable and a set of independent parameters such as slope angle and lithology here an inventory map of 87 landslides was used to produce a dependent variable which takes a value of 0 for the absence and 1 for the presence of slope failures lithology bed rock slope relationship lineaments slope gradient aspect elevation and road network were taken as independent parameters the effect of each parameter on landslide occurrence was assessed from the corresponding coefficient that appears in the logistic regression function the interpretations of the coefficients showed that road network plays a major role in determining landslide occurrence and distribution among the geomorphological parameters aspect and slope gradient have a more significant contribution than elevation although field observations showed that the latter is a good estimator of the approximate location of slope cuts using a predicted map of probability the study area was classified into five categories of landslide susceptibility extremely low very low low medium and high the medium and high susceptibility zones make up 8 87 of the total study area and involve mid altitude slopes in the eastern part of kakuda mountain and the central and southern parts of yahiko mountain

comparison of satellite and air photo based landslide susceptibility maps landslide susceptibility maps can be prepared in a variety of ways many geoscientists favour the use of an overlay model approach in which several map layers are combined by some arithmetic rules to determine the potential for sliding in an area or region the resulting susceptibility maps although based on a subjective weighting of relevant factors can often be of high accuracy and utility in order to obtain the relevant input data for this type of analysis remotely sensed data are often used to date susceptibility mapping just as the mapping of historic and individual landslides has tended to require higher resolution imagery this has somewhat limited the application of landslide susceptibility mapping while high resolution air photo or satellite imagery is superior to lower resolution imagery for the purpose of mapping of historic and individual landslides such higher levels of resolution may not be required for the development of landslide susceptibility maps in order to determine if medium resolution satellite imagery such as spot or aster could provide the needed data for landslide susceptibility mapping a comparison was undertaken of landslide susceptibility model output resulting from the use of stereo napp aerial photography versus the use of data obtained from stereo spot imagery the test area selected for this study consisted of two watersheds pena canyon and big rock canyon situated west of santa monica california usa along the pacific coast highway both watersheds have a long and well documented history of landslide activity and sufficient geologic variability and complexity to provide a good test site the specific overlay model used in this evaluation required input data consistent with the needs of many other models of this type the model output derived from the two different data sources and presented here in the form of susceptibility maps were virtually identical statistical and difference analysis confirmed that both methods of obtaining input data provide similar results and successfully identified landslide prone areas these results suggest that satellite imagery in this instance spot images could potentially be used in lieu of conventional air photos to evaluate landslide susceptibility in many situations especially in the case of remote locations and or developing countries this capability should result in substantial savings in terms of time financial resources and overall viability

environmental correlations of landslide frequency along new highways in the himalaya preliminary results abstract variables which correlate with accelerated landslide activity are identifed in a study of two new hill roads at almora and nainital u p india cumulatively 32 of the roadcut is affected by rockfall and 27 by the slumping of rock and or regolith correlation and discriminant analyses suggest that rockfalling may be predictable from measures of the frequency of enlarged joints in the roadcut supported by members of an inter related complex of variables including slope angle roadcut height apparent dip rock strength and upslope vegetation cover direct measures of environmental instability such as the undermining of the roadbed by erosion were also shown to have value however the study found few useful environmental indicators of slumping a positive relation between slumping and tree cover upslope may reflect the fact that forest survives as a relict landuse in locations which are undeveloped because of their instability

cenozoic paleogeography of the andean foreland and retroarc hinterland of colombia new biostratigraphic zonations core descriptions sandstone petrography facies analysis and seismic information are compared with published detrital and bedrock geo and thermochronology to build a cenozoic paleogeographic reconstruction of the andean retroarc region of colombia encompassing the ancestral central cordillera middle magdalena valley eastern cordillera and llanos basin we identify uplifted sediment source areas provenance domains depositional environments and thickness changes to propose a refined paleogeographic evolution of eastern colombia we conclude that cenozoic evolution of the northernmost andes includes 1 a period of contractional deformation focused in the central cordillera and middle magdalena valley that may have started by the late cretaceous although thermochronological data points to maximum shortening and exhumation during the late paleocene 2 a period of slower deformation rates or even tectonic quiescence during the middle eocene and 3 a renewed phase of contractional deformation from the late eocene to the pleistocene holocene expressed in provenance bedrock thermochronology and increased subsidence rates in the llanos foreland the sedimentary response in the llanos foreland basin is controlled by source area proximity exhumation and shortening rates relationships between accommodation and sediment supply as well as potential paleoclimate forcing this new reconstruction changes the picture of cenozoic basin evolution offered by previous reconstructions providing an updated chronology of deformation which is tied to a more precise understanding of basin evolution

the geological history of northwestern south america from pangaea to the early collision of the caribbean large igneous province 290 75ma abstract northwestern south america preserves a record of the assembly of western pangaea its disassembly and initiation of the far western tethys wilson cycle subsequent pacific margin magmatism and ocean plateau continent interaction since the late cretaceous numerous models have been presented for various time slices although they are based on either spatially restricted datasets or dates that are inaccurate estimates of the time of crystallisation here we review a very large quantity of geochronological geochemical thermochronological sedimentological and palaeomagnetic data that collectively provide tight constraints for geological models these data have been collected over a trench pacific parallel distance of 1500 km colombia and ecuador and reveal important temporal trends in rifting and subduction the temporal framework for our model constraints are obtained from robust concordant zircon u pb ages of magmatic rocks during 290 75 ma the late cretaceous thermal history of the margin

geology of the campanian m1 sandstone oil reservoir of eastern ecuador a delta system sourced from the amazon craton abstract the campanian m1 sandstone member of the napo formation is one of the main reservoirs of the capiron tiputini oil play system of the eastern part of the oriente basin of ecuador this study presents a geological model for this reservoir at the apaika and nenke oil fields included within the block 31 and the eden yuturi oil field operated by petroamazonas ep the geological characterization of the m1 sandstone is based on an integrated study which includes core description electric log analyses and seismic data interpretation the sedimentological descriptions from available cored sections show that m1 sandstone records a variety of fluvial to shallow marine processes including mass flow and delta front turbidity currents not previously documented the stratal stacking pattern interpreted from electric logs indicates that the succession reflects deltaic progradation rather than the backstepping pattern typically displayed by the underlying albian to santonian sediments of the napo formation seismic rms amplitude defines clinoform geometries with sigmoidal sand body architecture prograding from east to west correlation with neighboring regions in colombia suggest that the m1 sandstone was probably part of a large river dominated delta system sourced from the east during major campanian progradation the location of the source area of sediment was determined using u pb detrital zircon dating provenance ages are uniform within the m1 sandstone cluster in a population that ranges from 1 4 to 1 6 billion years these ages indicate that sands were derived mostly from erosion of the lithotectonic rio negro jurena province located to the northeast of the studied area detrital ages from the overlying maastrichtian tena formation include ages between 80 and 200 ma pointing to an important change in the source areas located in the eastern cordillera of ecuador the change in sediment supply from east to west recorded in the tena formation coincide with the initial episodes of the andean orogeny and may be driven by the collision of fragments of the caribbean large igneous province clip against the continental margin of northwestern south america

landslide processes and landslide susceptibility analysis from an upland watershed a case study from st andrew jamaica west indies abstract rainfall induced landslides are common geomorphic events on the steeper slopes of upper st andrew and cause severe environmental engineering social and economic repercussions in the area a geotechnical study was initiated to identify a past present and potential landslide types and sites for landslides b to examine the nature of geological geomorphological and geotechnical conditions under which failures can take place and c the potential landslide hazard in the area 886 failures were mapped more than 80 of which were located in soils a total of 1 55 km2 9 80 of the total area had failed approximately 59 failures per km2 were mapped with the highest density within elastic sedimentary units and weathered granodiorite 789 failure were mapped on slopes between 20 45 with no failure on slope less than 10 481 failures were mapped along twelve major roadways 46 6 km of road with approximately 10 failures km of road analysis of eighteen geotechnical units within nine geological formations revealed that the highest susceptibility for failure was within old landslide deposits with granular nonplastic to low plasticity soils and on slopes between 20 and 30 the lowest susceptibility was found within white limestones and recent alluvium and terrace deposits granular nonplastic to low plasticity soils are generally more susceptible than fine soils especially on slopes between 30 and 45 while granular and expansive clay soils demonstrate similar susceptibilities but on slopes between 30 and 45 and 20 and 45 respectively clastic sedimentary rocks are more susceptible that igneous lithologies an increase in slope angle increases the susceptibility to failures but only on slopes up to 45 an increase in the degree of weathering of soils and bedrock and fracturing of bedrock as well as road construction increases the landslide susceptibility in the area

spatial variation of suspended sediment concentrations in a tropical andean river system the paute river southern ecuador ecosistemas montanosos tropicales son sensibles a los cambios ambientales provocados por los procesos naturales y antropogenicos la topografia escarpada suelos poco profundos y las practicas no sostenibles de uso del suelo tras la conversion de bosques a menudo conducen a mejora de la tasa de actividad geomorfologica incluyendo la erosion del suelo deslizamientos y actividad fluvial el rapido crecimiento demografico y el desarrollo socio economico se han acelerado los cambios ambientales en los ultimos decenios durante los ultimos 50 anos la erosion del agua en los campos agricolas causados por practicas agricolas inadecuadas se percibe como la principal fuente de sedimentos fluviales en las cuencas tropicales andinos sin embargo debido a datos esporadicos sobre la produccion de sedimentos transporte y export en cuencas tropicales andinos no esta claro en cuanto a si la actividad geomorfologica es controlada principalmente por factores naturales o antropogenicos un programa de investigacion se ha llevado a cabo en el 5176 kilometros 2 rio paute cuenca situada en el sur de ecuador para examinar la variabilidad en la carga de sedimentos en los rios un programa de monitoreo se creo en la parte central de la cuenca para extraer informacion sobre la variabilidad espacial en la carga de sedimentos del rio en relacion con las variables de influencia que describen el clima la litologia la topografia y el uso del suelo veintinueve tramos fluviales se muestrearon durante dos temporadas de lluvias sucesivas en cada visita se tomaron muestras de sedimentos en suspension y se midio la descarga del rio instantanea se recogieron datos geograficos relacionados con la topografia la morfologia del paisaje las precipitaciones la cobertura del suelo y la geologia las cuencas que fueron afectados por una intensa erosion deslizamiento de tierra en la zona aguas arriba tienen una concentracion de sedimentos en suspension ponderada significativamente mayor que las cuencas restantes existe cierta evidencia que sugiere que la aparicion de estas grandes deslizamientos de tierra poco frecuentes se relaciona principalmente con la pendiente topografica en lugar de a las practicas de uso del suelo actuales o actividades humanas

along strike variations in the thermal and tectonic response of the continental ecuadorian andes to the collision with heterogeneous oceanic crust oblique to strike geological segmentation in the andean chain has been previously recognised at various scales and is commonly attributed to changes in the convergence vectors of the oceanic and continental plates as well as the upperplate expressions of differing along strike subducted slab age strength and composition we present new white mica and biotite 40 ar 39 ar and zircon and apatite fission track data from several traverses across the cordillera real of ecuador in the northern andes that reveal distinct along strike differences in the timing of accelerated crustal cooling during the cenozoic the data record elevated cooling rates from temperatures of v380 c during v65 55 and v43 30 ma from all sampled regions of the cordillera real and at v15 ma and since v9 ma in the northern cordillera real each cooling period was probably driven by exhumation in response to the accretion and subduction of heterogeneous oceanic crust elevated cooling rates of up to v30 20 c myr were initiated during the palaeocene and eocene early oligocene along the entire contemporaneous margin of ecuador and were driven by the accretion of the oceanic pallatanga terrane and pin on macuchi block respectively onto northwestern south america both of these geological provinces originated at the southern parts of the leading and trailing boundaries of the caribbean plateau and accreted onto the margin during the approximately northeastward migration of the plateau into its current position within ecuador the development of higher topography and elevated cooling rates of up to 50 c myr at v15 ma and since v9 ma are restricted to the region north of 1 30ps and is situated above the postulated subducted flatslab section of the aseismic carnegie ridge plate convergence rate calculations suggest the carnegie ridge collided with the ecuador trench at v15 ma which caused the pre existing coastal provinces to displace to the northeast subsequently driving extension and marine ingressions in southern ecuador and compression and uplift in northern ecuador fl 2001 elsevier science b v all rights reserved

the early interaction between the caribbean plateau and the nw south american plate the determination of accurate and precise ages for the timing of collision between oceanic plateaus and continental crust requires an understanding of how the indenting and buttressing plates respond to the collision we present geochronological thermochronological geochemical and isotopic analyses of magmatic rocks from the ecuadorian andes which relate to the collision of the late cretaceous caribbean plateau and great arc sequence with nw south america the cessation of subduction magmatism during 65 64 ma beneath the eastern edge of caribbean plateau was synchronous with accelerated surface uplift and exhumation within the buttressing continental margin during 75 65 ma we interpret this as the collision of the leading edge of the caribbean plateau and arc sequence with the south american plate at 75 65 ma a u pb zircon shrimp age of 87 10 1 66 2 sigma ma yielded by an accreted fragment of the plateau precludes previous estimates of collision at 85 80 ma if the plateau erupted above the galapagos hotspot less

slump and debris flow dominated upper slope facies in the cretaceous of the norwegian and northern north seas 61 67 n implications for sand distribution a regional sedimentological study of cretaceous sequences in the mid norway region norwegian sea and in the agat region agat field area northern north sea reveals that these sequences were predominantly deposited in an upper continental slope environment by slumps and debris flows examination of nearly 500 m of core from 14 wells shows eight distinct lithofacies facies 1 contorted conglomerate and pebbly sandstone represents deposits of sandy slumps and debris flows possibly in a channel setting facies 2 contorted sandstone is the most widespread and is the product of sandy slumps and debris flows facies 3 contorted mudstone indicates deposition from muddy slumps and debris flows facies 4 rippled sandstone suggests bottom current reworking facies 5 gr ded sandstone represents turbidity current deposits and is very rare facies 6 laminated mudstone is a product of pelagic or hemipelagic deposition facies 7 cross bedded sandstone is indicative of tidal processes and facies 8 laminated sandstone represents delta front and shelf deposits these facies and their association suggest a shelf edge delta to upper slope environment of deposition existing core data document deltaic facies only in the mid norway region the proposed shelf edge delta and upper slope model has important implications for sand distribution 1 this model provides an alternative to the conventional submarine fan model previously applied to these sequences 2 although slump and debris flow emplaced sands are usually discontinuous and unpredictable highly amalgamated slump and debris flow sands may develop thick reservoirs 3 by using the eocene frigg formation as an analog it is predicted that externally mounded seismic facies in the study area may be composed of sandy slumps and debris flows

downstream fining selective transport and hillslope influence on channel bed sediment in mountain streams colorado front range usa abstract channel bed sediment is composed of a combination of upstream and local hillslope sources factors that influence downstream changes in size sorting and lithological characteristics of bed material are complex in order to better understand this complexity we measured grain sizes and channel geometry on five streams draining the colorado front range the studied streams flow from steeply incised canyons in the mountains onto the gently sloping colorado high plains downstream fining occurs at the scale of the entire study reach 30 km but not in each individual stream differences between streams are likely related to watershed size and discharge characteristics at smaller spatial scales within each stream the fining pattern is less clear and is disrupted by lateral inputs from locally steep hillslopes in the incised canyons of the front range however the exclusion of local hillslope influence by distinguishing among individual lithologies in the channel bed material that are not present in the local hillslopes shows that fining also occurs over these smaller spatial scales in the absence of steep hillslopes adjacent to the channels bed sediment becomes a better mix of lithologies from the whole watershed rather than dominated by local hillslope sediment influx we propose four dominant factors that control the channel bed characteristics in the study area inheritance hydrodynamics lithologically controlled sediment abrasion rates and differences in denudation rates throughout the watershed with associated differences in hillslope steepness combining these factors leads to a conceptual model that explains our observations and illustrates the complexity of the behaviour of bed material in steep mountainous regions and their bounding basins distinguishing among the different lithologies in the bed material was instrumental in decomposing and understanding the complex trends in this system

runoff and sediment yield from rural roads trails and settlements in the upper konto catchment east java indonesia abstract the potential importance of roads and settlements for the generation of storm runoff and sediment in tropical steeplands is increasingly recognised but rarely quantified this paper presents runoff and sediment yield data for a cobbled and an unpaved road section two large unbounded settlement plots and several trails draining residential areas or terraced fields in a volcanic upland catchment in east java in addition the sediment yield of major landslides associated with roads was quantified the unpaved road section exhibited an average runoff coefficient of about 65 and yielded about 7 kg m 2 yr 1 of sediment both the runoff coefficient and the sediment yield for the cobbled road section plus adjacent yards were lower 38 and 1 9 kg m 2 yr 1 sediment output from a 4160 m2 hillside plot including a network of trails draining terraced fields for which runoff and sediment outputs were shown to be negligible was similar to that for the cobbled road 2 3 kg m 2 yr 1 depending on rainfall however a much higher value was obtained when the overall soil loss from the plot was expressed per square metre of trail surface area ca 42 kg m 2 yr 1 whereas the associated trail runoff coefficient was about 70 the results obtained for several trails and large unbounded plots draining residential areas at two locations were less extreme runoff coefficients of 24 43 soil loss 1 3 3 5 kg m 2 yr 1 landsliding occurred mainly at the end of the rainy season march and was estimated to have contributed ca 2365 m3 of sediment to the main road network during the 1988 89 wet season vs ca 905 m3 in 1989 90 and only ca 150 m3 in 2000 01 it is concluded that despite their relatively small areal extent 5 in the study area rural roads trails and settlements are significant producers of runoff and sediment at the catchment scale and should be included in watershed management programmes designed to reduce catchment sediment yields and reservoir siltation

sediment transport in the surf zone a quasi 3 d numerical model in the preceding paper detailed long crested wave and quasi 3 d surf zone current calculations were presented as the initial steps to a more complete numerical model for coastal processes here these results are used to calculate detailed sediment transport rates in the surf zone and the resulting bathymetry evolution with time the pc based quasi 3 d numerical model results are calibrated with laboratory experiments performed on a simulated infinitely long natural beach tests were carried out using regular and irregular wave fields with different wave conditions and sand sizes