dating methods and geomorphic evidence of palaeoenvironmental changes at the eastern margin of the south peruvian coastal desert 14 30 s before and during the little ice age abstract the atacama desert is known to be one of the driest places on earth however in the study area between ica and nasca south peru 75 76 w 14 15 s palaeoclimate proxies show several semi arid phases during the holocene a more humid period during the early holocene favoured an open grass land which allowed the accumulation of desert loess eitel b hecht s machtle b schukraft g kadereit a wagner g kromer b unkel i reindel m 2005 geoarchaeological evidence from desert loess in the nazca palpa region southern peru palaeoenvironmental changes and their impact on pre columbian cultures archaeometry 47 137 158 the paracas and nasca cultures existing in that region between the 9th century bc and 7th century ad had propitious conditions to evolve and to settle close to the rivers fed by the monsoonal precipitation in the cordillera occidental culminating aridity after 600 ad might have caused the collapse of the nasca civilization the onset of semi arid climate towards the end of the late intermediate period 14th century ad allowed a reoccupation of the area here we present 14c and osl data from sediments of river terraces a debris flow and loess snails scutalus sp indicating appreciable geomorphic activity between 1390 and 1714 cal ad this phase is isochronous to the little ice age period on the northern hemisphere and to an increase in the ice accumulation on the quelccaya glacier in the peruvian altiplano thompson l g mosley thompson e bolzan j f koci b r 1985 a 1500 year record of tropical precipitation in ice cores from the quelccaya ice cap peru science 229 971 973

optical dating using infrared diodes young samples abstract ages are reported for unburnt sediment samples from 9 archaeological sites in england spanning 1000 5000 years samples from two modern contexts have also been measured

discovery of middle jurassic trench deposits in the bangong nujiang suture zone implications for the timing of lhasa qiangtang initial collision abstract the mesozoic trench deposits in the bangong nujiang suture zone in central tibet can provide critical information for reconstructing the paleotectonic evolution of the bangong nujiang ocean and constraining the timing of the lhasa qiangtang initial collision in this paper the gamulong formation which is well exposed in the dong co area western bangong nujiang suture central tibet was studied the sedimentological analysis shows that the gamulong formation was deposited in a submarine fan environment the youngest detrital zircon age and fossils from limestone pebbles within the gamulong formation combine to determine a middle jurassic age the pebbles in the conglomerate are dominated by limestones and sandstones which is consistent with the sandstone petrology showing limestone and sandstone fragments as the main framework components detrital zircon u pb ages from the sandstones yield age populations of 164 178 ma 200 500 ma 700 1000 ma 1700 2100 ma and 2500 ma the corresponding zircon ehf t values are distributed between 23 5 and 11 1 these zircon features are similar to those from the qiangtang terrane accordingly the provenance results imply that the gamulong formation was recycled from the accretionary complex mugagangri group melange in the bangong nujiang suture zone and the forearc basin deposits lower middle jurassic sewa shaqiaomu jiebuqu formations in the southern qiangtang subterrane the gamulong formation is characterized by sedimentary recycling in the trench likely in response to a tectonic event possibly the continental collision together with the previous studies this work on the occurrence of the gamulong formation indicates that the lhasa qiangtang initial collision could have occurred in middle jurassic time 166 ma

late quaternary aeolian sedimentation in central and south eastern tibet abstract the geomorphology and the cover sediments in the central and south eastern part of the tibetan plateau provide information about climatic change luminescence dating of aeolian and colluvial silts on top of different moraine sequences provides the first indications for the timing of these sediments during the late quaternary and holocene although there is a widespread cover of aeolian mantles in tibet only a few papers have focussed on them up to now samples from silt layers on top of pleistocene moraines or solifluction debris from central and southern tibet at elevations above 4000 m asl provide early holocene ages in most sections the aeolian silt on top of the bomi moraine in southeastern tibet situated at an elevation of about 3000 m asl provides an age of 25 ka according to geomorphological investigations the bomi moraine dates from the last ice age which can be confirmed by the luminescence data moreover one sample from a silt layer in between gravel layers xainxa is also pleistocene in age according to its sedimentary and geomorphological situation in the tibetan plateau pleistocene loess mainly occurs below 4000 m asl the holocene material a more sandy silt lying above 4000 m asl however aeolian material capping the moraines provides only minimum ages for the terminal moraines the time interval between glacier retreat and the accumulation of aeolian sediments may be several thousand years the most important fact is the trapping of dust in general lakes and a denser vegetation cover are or were the main traps for the typical loess found in the mountain areas of the tibetan plateau

the morphology mineralogy and behavior of u fine grained gold from placer deposits of alberta sampling and implications for mineral exploration the morphology of a large number of gold grains from stream sediments of the north saskatchewan river and the athabasca river was studied together with the partitioning of the placer gold between various size fractions two major morphological varieties of gold were observed 1 flaky scaly gold with folded and hammered edges and with crystals or crystal faces still visible on the surface and 2 sandwiched droplike particles sometimes toroidal about 5 of both types of gold were found to be coated with new secondary gold the size of the majority of the gold grains studied varies between 0 500 and 0 010 mm the most frequent size range in the north saskatchewan river is 0 125 0 250 mm whereas in the athabasca river it is 0 063 0 125 mm an important fraction of the gold from both rivers is smaller than 0 063 mm the average corey shape factor csf of the gravity recovered gold increases as the particle size decreases whereas the gold grains lost to the tailings indicate very low average sha

infrared stimulated luminescence dating of holocene colluvial sediments using the 410 nm emission abstract infrared stimulated luminescence irsl ages are reported for loessic colluvial sediments from wiesenbach south germany the samples were collected by boring and the polymineral fine grain fraction t4 1 i m was used for irsl investigations irsl spectra were measured prior to dating they show two major emissions at approx 560 and 410 nm the advantages of the subtraction dating technique aitken and xie 1992 using the 410 run emission are demonstrated the ages obtained are used for the reconstruction of the landscape development at the studied site subsequent to an erosion phase the deposition of a colluvium started prior to the roman period and increased to a maximum accumulation rate during the middle ages

luminescence dating of poorly bleached sediments from scotland abstract two types of poorly bleached sediment are differentiated and the applicability of various luminescence dating methods is assessed the methods are applied to three fluvioglacial sediments from scotland it is shown that it is possible to detect sediments that contain a mixture of well bleached and unbleached grains using the single aliquot additive dose method or the analysis of the scatter in aultiple aliquot additive dose growth curve

timing of formation of forebergs in the northeastern gobi altai mongolia implications for estimating mountain uplift rates and earthquake recurrence intervals bedrock and quaternary alluvial fans in the forelands of the northern gobi altai have been faulted and warped by foreland propagating thrust faults to form elongate hills known as forebergs forebergs near bogd town north of arsta bogd and at ih hetsuu north of baga bogd were mapped and their formation constrained using luminescence dating of lacustrine and fanglomerates sediments to give localized uplift rates of c 0 05 m ka 1 and between c 1 6 and 4 1 m ka 1 respectively comparisons between vertical surface rupture during the 1957 gobi altai earthquake with the age and amount of uplift of lacustrine sediments provide a tentative estimate of between 1288 382 to 497 120 years for the average recurrence interval of great earthquakes in the baga bogd region these localized uplifts rates support the view that the gobi altai mountains probably took between 50 and 25 million years to form and were therefore coeval with the uplift of the himalayas and the tibetan plateau

thermoluminescence dating tests of pleistocene sediments from uplifted marine shorelines along the southwest coastline of the calabrian peninsula southern italy abstract this paper presents tl age estimates of pleistocene raised marine terraces from southern calabria southern italy it focuses on the dating of last interglacial shallow marine sand deposits including several tyrrhenian key reference deposits whose stratigraphic assignment is based on biostratigraphic evidence presence of a strombus bubonius fauna and geochronometric data amino acid data calibrated with u th dates on coral the tl age estimates are obtained on alkali feldspar coarse grains using their blue tl emission they are in good agreement with the ir osl age estimates obtained on the same feldspar samples our feldspar tl method is tested on two tyrrhenian key reference sites ravagnese and bovetto in the reggio di calabria area their measured tl age estimates 97 11 ka and 100 10 ka are lower than their estimated geological age i e oxygen isotope substage 5e the correction for long term fading suggested by mejdahl 1988 is tested on these two samples using a lifetime of 446 ka as estimated from both calabrian and miocene sand collected within the same area this correction would yield preliminary tl ages 116 13 ka and 116 12 ka that are in better agreement with the expected geological age the application of our tl method to paleoshorelines lying below the tyrrhenian reference shoreline of ravagnese bovetto yields stratigraphically consistent tl age estimates the tl method is also applied to two supposedly pre last interglacial paleoshorelines which are geomorphologically older than the tyrrhenian reference shorelines they remain however chronologically undifferentiated both by the tl and the amino acid methods finally the preliminary feldspar tl results obtained on the miocene and the calabrian sand deposits 1 ma suggest that our feldspar tl method is limited in the sw calabrian area to about 200 ka

anatomy and evolution of a lower cretaceous alluvial plain sedimentology and palaeosols in the upper blairmore group south western alberta canada the lower cretaceous albian upper blairmore group is part of a thick clastic wedge that formed adjacent to the rising cordillera in south western alberta regional transgressive intervals are superimposed on the overall regressive succession alluvial conglomerates sandstones and mudstones were deposited in east north eastward draining fluvial systems orientated transverse to the basin axis five facies associations have been identified igneous pebble conglomerate thick sandstone interbedded lenticular sandstone and mudstone thick mudstone with thin sandstone interlayers and fossiliferous sandstone and mudstone the facies associations are interpreted as gravelly fluvial channels sandy fluvial channels sand dominated floodplains mud dominated floodplains and marine shoreline deposits respectively five types of palaeosols are recognized in the upper blairmore group based on lithology the presence of pedogenic features clay coatings root traces ferruginous nodules slickensides carbonate nodules and degree of horizonization the regional distribution of the various types of palaeosols enables a refinement of the palaeoenvironmental reconstruction permitting an assessment of the controls on floodplain evolution in source proximal areas palaeosol development was inhibited by high rates of sedimentation in source distal locations poor drainage resulting from high watertables low topography and lower rates of sedimentation also inhibited palaeosol development the best developed palaeosols containing bt horizons occur in intermediate alluvial plain positions tectonic hinge zone where the floodplains were most stable due to a balance between sedimentation erosion and subsidence rates extrapolating from the upper blairmore group suggests that the tectonic hinge zone of continental foreland basins can be established by palaeosol analysis at the hinge zone soil development is controlled primarily by climate and tectonics and their effect on sediment supply whereas closer to the palaeoshoreline relative sea level fluctuations resulting in poor drainage may have a more significant influence

westerly derived early cretaceous gold paleoplacers in the western canada foreland basin southwestern alberta tectonic and economic implications albian aged early cretaceous igneous pebble to cobble conglomerates fill multiple northeast southwest oriented subparallel channels in the upper blairmore group upper beaver mines and mill creek formations of the rocky mountain foreland basin southwestern alberta and southeastern british columbia paleocurrent data show that the conglomerate was derived from the west clast petrography implies a provenance that includes granitoids mafic volcanics low grade metamorphic rocks and shallow level ca 7 km depth postmetamorphic quartz veins formed from meteoric fluids the conglomerate was probably derived from the southern omineca belt of british columbia prior to the rise of the rocky mountains the conglomerate contains detrital gold grains up to 150 m in diameter and chemical analyses indicate widespread anomalous gold concentrations up to 910 ppb au in conglomerate matrix gold content in these igneous clast conglomerates excedes that reported from the richest modern placers in alberta les

diagenetic alteration of a mesozoic fluvial gold placer deposit southern new zealand abstract gold paleoplacers become progressively more affected by diagenetic processes with age and burial mesozoic paleoplacer deposits in southern new zealand display intermediate stages of diagenetic transformation compared to little affected late cenozoic paleoplacers and strongly affected paleozoic and precambrian paleoplacers the mesozoic cretaceous diagenesis resulted in near pervasive alteration cementation and lithification of the paleoplacer lithic clasts and matrix have been extensively altered to illite ferrous iron bearing smectite vermiculite and kaolinite and the cement consists mainly of clays and calcite diagenetic pyrite marcasite vivianite and mn oxide also contributed to cementation alteration occurred under near surface

middle and late holocene dune reactivation in the nebraska sand hills usa a combination of optical dating of aeolian sand and radiocarbon dating of palaeosols and interdune sediments has allowed some refinements to the chronostratigraphy of the nebraska sand hills our results directly confirm previous inferences that multiple phases of aeolian deposition including megabarchan dune reactivation occurred within the sand hills during the middle and late holocene optical dates on stratified aeolian barchan dune sediments from two localities provide ages ranging from c 6 ka to 300 years ago weakly developed palaeosols intercalated within the dune sediments and other forms of post depositional modification indicate periods of relative stability and reduced dune mobilization optical dates on the upper 12 15 m of two dune exposures indicate repeated possibly regionally correlative reactivations which occurred between c 400 500 and 200 300 years ago comparison of late holocene aeolian activity with local and regional palaeoclimatic proxy records suggests that dune reacti

optical dating of young modern sediments using quartz results from a selection of depositional environments abstract equivalent dose ed evaluations for quartz grains extracted from a number of modern or young samples collected from a range of depositional environments are reported the signal used was optically stimulated luminescence osl with an argon ion laser tuned to 514 nm as a light source typical equivalent dose values were 0 05 0 3 gy for the given samples which is substantially less than equivalent doses expected for similar sediments by conventional thermoluminescence tl the non zero equivalent dose exhibited by the samples may be a product of relict osl from incompletely bleached traps sample pre treatment procedures or due to signal recuperation following bleaching during antiquity the potential significance of each are discussed a number of modifications to sample pre treatment and processing are also described

gold nugget growth during tectonically induced sedimentary recycling otago new zealand abstract an alluvial fan 5 km wide and 3 5 km long has been derived over the past 65 000 years from an actively rising schist mountain range dunstan range in central otago new zealand the fan can be locally subdivided into four distinctive consecutively formed gravel sequences the earliest of which has been deformed along the range margin these gravels are pre dated by miocene mature fluvial sediments manuherikia group which have been recycled into the alluvial fan gravels during uplift all these sedimentary sequences contain gold which has been mined sporadically manuherikia gold grains up to 13 wt ag are well rounded and typically 300 m across typical grain size of gold becomes progressively coarser with each gravel sequence in the alluvial fan and nuggets up to 2 cm occur in younger gravel sequences gold grain size increase is due to addition of authigenic gold on to pre existing grains authigenic gold occurs as a cement between earlier detrital grains 1 4 wt ag as amorphous coatings and protrusions 0 1 wt ag and as overgrowths of lattice intergrowths 0 1 wt ag gold nuggets formed in the gravels have overgrown detrital minerals and authigenic clay minerals chemical accretion of nuggets may be still continuing today in parts of the alluvial fan

transport and concentration of detrital gold in foreland basins abstract economic concentrations of detrital gold are rare in young foreland basins due to paucity of significant gold sources and a paucity of sediment recycling processes during filling of the foreland basin gold shed into the foreland basins is typically widely dispersed in an overwhelming volume of immature basin fill detritus of no economic significance in the actively forming canterbury basin of new zealand minor gold concentration occurs at the mountain front in the bed of the rakaia river and 60 km downstream on beaches and the crest of foredunes at the river mouth the cretaceous tertiary denver and western canada basins in north america also have minor gold concentrations at the mountain front and minor gold dispersal into the basin tectonic quiescence in the middle tertiary in the denver basin kept gold within 20 km of the mountain front where renewed uplift in late tertiary caused minor economic concentrations to form in modern streams gold has been transported ca 200 km across the western canada basin by progressive recycling of gravel during slow ca 10 to 50 m ma middle tertiary recent regional uplift and tilting but little concentration has occurred development of significant placers in a foreland basin the generally accepted setting for the witwatersrand au u palaeoplacers appears to require specific tectonic conditions during and or after basin evolution to drive the sedimentary recycling necessary for significant placer development such tectonic conditions have not occurred in an any of the three young foreland basins examined in this study

correlation of fluvial terraces within the hikurangi margin new zealand implications for climate and baselevel controls abstract a correlation of fluvial terraces is presented for eight non glacial catchments of the eastern north island new zealand within the actively uplifting hikurangi margin using a combination of loess and tephra coverbed stratigraphy and radiocarbon and osl dating of fluvial deposits and loess coverbeds we demonstrate correlation of four fill terraces t1 t4 the available age constraints suggest t1 15 30 ka t2 31 50 ka t3 50 70 ka and t4 115 ka but the association and temporal link with loess deposits suggest correlation with cold periods and thus the refinement of t2 late mis 3 31 40 ka t3 mis 4 55 70 ka t4 mi substage 5b 90 ka 5d 110 ka or mis 6 140 160 ka the ability to correlate terraces between catchments plus the lack of independent evidence for tectonic triggering events indicates terraces have probably formed in response to either climate terrestrial or baselevel sea level control climate control is indicated by the temporal link of post glacial incision with re establishment of forest cover and of lgm aggradation with limited grass and shrub cover and periglacial processes aggradation due to increased sediment supply under reduced vegetation is dramatically demonstrated by formation of the taupo pumice alluvium terrace in response to inundation by volcanic deposits unwelded ignimbrite following the 1 8 ka taupo eruption and the response to post settlement

environmental changes at the eastern namib desert margin before and after the last glacial maximum new evidence from fluvial deposits in the upper hoanib river catchment northwestern namibia in the upper hoanib river catchment area northwestern namibia fine grained silty deposits are widespread accumulated as river end deposits they form excellent geomorphological archives of a highly sensitive desert margin area different sedimentary complexes are separated sedimentologically and by luminescence dating the deposits give evidence of climate oscillations at the eastern margin of the namib desert during the past 50 000 years in northwestern namibia the dry conditions of the desert margin area with less than 200 300 mm mean annual precipitation prevailed at 60 40 ka and at 34 24 ka when sediment complex i accumulated during the last glacial maximum lgm fluvial activity and sedimentation were most likely interrupted due to arid conditions between 12 ka and the mid holocene higher rainfall and runoff led to the aggradation of sediment complex ii the climate was more humid than before the lgm but drier than at present after 3 ka runoff increased and the hoanib river re eroded the older deposits forming deep channels a prominent more sandy and gravely 4 m terrace in the upper and middle course of the hoanib river dates to the little ice age lia it is likely that this terrace is genetically linked with the amspoort silt formation in the lower hoanib valley d 2005 elsevier b v all rights reserved

river drainage reorientation during placer gold accumulation southern new zealand many alluvial placer deposits around the world occur in river systems that have been affected by tectonic events causing drainage reorientation and severance of links between placers and their sources this study documents tectonic rejuvenation of topography in the otago giant placer goldfield new zealand which has resulted in numerous river capture and drainage reorientation events these events have induced changes to gold transport directions and numerous stages of separation of detrital gold from primary sources goldfield wide reconstructions of drainage patterns through time are as yet only possible for miocene recent and numerous earlier drainage changes back to cretaceous primary orogenic mineralisation are probable variations in basement lithologies permit auriferous gravel provenance determinations facilitating paleodrainage pattern reconstruction and documentation of river capture events river capture events and timing of these events for gold bearing paleodrainages have also been documented using genetic divergences of populations of freshwater galaxiid fish that were isolated by drainage reorientation gold bearing quartz pebble conglomerates had a southeastward drainage in the miocene this was disrupted in the pliocene by mountain range uplift and gold placer recycling with deposition of lithic conglomerates containing only minor gold placers the most dramatic changes in gold transport directions occurred through the quaternary as antiformal ranges grew across the pre existing drainages miocene and pliocene placers were recycled with numerous local 1 10 km scale changes in river directions and numerous capture events large axial rivers were segmented into a more complex drainage pattern and on going river capture resulted in growth of the main clutha river catchment at the expense of neighbouring catchments the most productive placers developed in the clutha river in late quaternary when increased discharge from captured mountain catchments enhanced gold transport and concentration similar river drainage reorientation has occurred in other placer fields around the world but the lack of preserved evidence inhibits documentation of most such changes

age of pre late wisconsin glacial estuarine sedimentation bristol bay alaska pleistocene glacial estuarine sediment deposited in an intertidal environment of northeastern bristol bay southwestern alaska was dated using a variety of approaches including infrared stimulated and thermoluminescence irsl and tl techniques analysis of modern and14c dated holocene tide flat mud demonstrates that the bulk of sediment in this environment is reset by solar radiation thereby lending confidence to ages obtained from similar pleistocene deposits by luminescence techniques irsl seems to be especially well suited for dating with resolution on time scales of 10 000 yr the ages of tide flat mud of the nushagak formation derived from the ahklun mountains to the northwest of bristol bay and of halfmoon bay drift derived from the alaska peninsula to the southeast suggest contemporaneous glacial estuarine deposition related to independent glacial source areas about 75 000 80 000 yr ago this age is consistent with other geochronological data that indicate a pre late wisconsin and post substage 5e age including nonfinite14c ages a lack of interglacial indicators and old crow tephra 140 000 yr atop the drift normal paleomagnetic inclinations and amino acid isoleucine epimerization ratios aile ile aile ile ratios inportlandia arctica 0 052 0 003 from a marine lag horizon at south naknek beach which separates halfmoon bay drift above from older glacial estuarine drift below are only slightly higher than inmya truncata 0 041 0 007 from last interglacial pelukian deposits at nome as laboratory heating experiments show that the two genera epimerize at similar rates these data imply correlation of the marine lag at south naknek beach with pelukian deposits hence glaciers on the alaska peninsula experienced major pre late wisconsin advances both before and after the last interglaciation shells reworked into halfmoon bay drift yield aile ile ratios of 0 028 0 005 forportlandiaat second point and 0 027 0 001 forhiatella arcticaat etolin point together with assumptions about the postdepositional temperature history these ratios indicate that the shells are at least 55 000 yr and probably closer to 90 000 yr although the uncertainty in this age estimate is broad the amino acid and luminescence data converge on an age between about 75 000 and 90 000 yr late during oxygen isotope stage 5 for a major ice advance far beyond late wisconsin limits

characterising and dating weichselian organogenic sediments a case study from the lusatian ice marginal valley scheibe opencast mine eastern germany abstract dates determined with three absolute dating methods 14c luminescence and 230th u supported the findings of the paleobotanical investigations of the weichselian upper fluvial sequence of the scheibe opencast mine in the niederlausitz lower lusatia eastern germany they allowed to identify three units of organogenic sediments organogenic complexes oc developed as peaty and or humic silts samples from the uppermost oc i unit displayed 14c age ranges from 32 to 28 and 26 to 24 ka respectively for the latest phase an open landscape was identified although high arboreal values point to locally extended sparse forests the lithologically and paleobotanically heterogeneous oc ii unit 37 ka represents at least two periods during which organic matter accumulated in an open landscape the uppermost subunit represents an unforested interstadial of the middle pleniglacial the lowermost oc iii unit has an age of about 56 ka or higher according to the 230th u or tl dates respectively it represents a forested interstadial assigned to the early weichselian

coeval emplacement and orogen parallel transport of gold in oblique convergent orogens abstract varying amounts of gold mineralisation is occurring in all young and active collisional mountain belts concurrently these syn orogenic hydrothermal deposits are being eroded and transported to form placer deposits local extension occurs in convergent orogens especially oblique orogens and facilitates emplacement of syn orogenic gold bearing deposits with or without associated magmatism numerical modelling has shown that extension results from directional variations in movement rates along the rock transport trajectory during convergence and is most pronounced for highly oblique convergence with strong crustal rheology on going uplift during orogenesis exposes gold deposits to erosion transport and localised placer concentration drainage patterns in variably oblique convergent orogenic belts typically have an orogen parallel or sub parallel component the details of which varies with convergence obliquity and the vagaries of underlying geological controls this leads to lateral transport of eroded syn orogenic gold on a range of scales up to 100 km the presence of inherited crustal blocks with contrasting rheology in oblique orogenic collision zones can cause perturbations in drainage patterns but numerical modelling suggests that orogen parallel drainage is still a persistent and robust feature the presence of an inherited block of weak crust enhances the orogen parallel drainage by imposition of localised subsidence zones elongated along a plate boundary evolution and reorientation of orogen parallel drainage can sever links between gold placer deposits and their syn orogenic sources many of these modelled features of syn orogenic gold emplacement and varying amounts of orogen parallel detrital gold transport can be recognised in the miocene to recent new zealand oblique convergent orogen these processes contribute little gold to major placer goldfields which require more long term recycling and placer gold concentration most eroded syn orogenic gold becomes diluted by abundant lithic debris in rivers and sedimentary basins except where localised concentration occurs especially on beaches

the role of the shuswap metamorphic complex in cordilleran tectonism a review the shuswap metamorphic complex consists of three parts each with unique stratigraphy and orogenic evolution separated by major faults of diverse nature and having in common only a post late mesozoic tectonic history the first part the monashee complex is a possible extension of the precambrian shield that contains limited evidence of mesozoic orogenesis and that was rapidly uplifted during the cretaceous to paleogene the monashee decollement a warped mylonite zone interpreted as a regional thrust fault active through the middle jurassic separates this complex from the second part which contains rocks correlative with hadrynian to late paleozoic strata of the pericratonic prism the third part the okanagan complex straddling the 49th parallel from the okanagan valley to kootenay lake contains the probable exhumed roots of a mesozoic magmatic arc built upon possible north american continental and transitional crust and includes late paleozoic and early mesozoic suspect terranes the columbian or