identification of inherited radiogenic pb in monazite and its implications for u pb systematics the simplest interpretation of uranium lead mineral ages in igneous rocks embodies the assumption that melting of pre existing rocks leads to homogenization of the lead isotopes thus resetting the radiometric clock zircons often violate this assumption by only partially dissolving and preserving a component of lead inherited from before the melting episode but until now such behaviour has not been observed in monazite here we report u pb data for zircons and monazites from a tertiary granite from the himalayas in which zircons and monazites contain inherited radio genic lead an analysis of a single entirely igneous zircon crystal plots on concordia at 19 5 0 4 myr eight monazite fractions lie on a line from an upper intercept of 471 10 myr to the youngest fraction which plots slightly above concordia at 21 myr the presence of excess 206pb in the youngest monazite fractions indi cates that the monazite data represent a mixing line between young magmatic monazite and an older inherited component rather than a resetting of 471 myr monazites at 20 myr these data suggest a closure temperature for pb in monazite significantly higher than previously published estimates

structure of the north indian continental margin in the ladakh zanskar himalayas implications for the timing of obduction of the spontang ophiolite india asia collision and deformation events in the himalaya the collision of india and asia can be defined as a process that started with the closing of the tethyan ocean that during mesozoic and early tertiary times separated the two continental plates following initial contact of indian and asian continental crust the indian plate continued its northward drift into asia a process which continues to this day in the ladakh zanskar himalaya the youngest marine sediments both in the indus suture zone and along the northern continental margin of india are lowermost eocene nummulitic limestones dated at similar 54 ma along the north indian shelf margin southwest facing folded palaeocene lower eocene shallow marine limestones unconformably overlie highly deformed mesozoic shelf carbonates and allochthonous upper cretaceous shales indicating an initial deformation event during the latest cretaceous early palaeocene corresponding with the timing of obduction of the spontang ophiolite onto the indian margin it is suggested here that all the ophiolites from oman along western pakistan bela muslim bagh zhob and waziristan to the spontang and amlang la ophiolites in the himalaya were obducted during the late cretaceous and earliest palaeocene prior to the closing of tethys

middle late miocene 10 ma formation of the main boundary thrust in the western himalaya three independent data sets from northwestern india and pakistan suggest initial displacement along 1000 km of the main boundary thrust prior to 10 ma at least 5 m y earlier than previously reported regionally extensive changes in the depositional characteristics and rates of the foreland basinfill between 11 and 9 5 ma are interpreted to reflect new hinterland loading due to the formation of the main boundary thrust sediment accumulation rates sandstone siltstone ratios and thickness and amalgamation of individual sandstone bodies all substantially increase after 11 ma in well dated stratigraphic sections from pakistan to nepal across the indo gangetic foreland basin in the himachal pradesh reentrant of northwestern india a newly discovered 8 7 ma conglomerate derived from the hanging wall of the main boundary thrust indicates that source area uplift and denudation must have occurred prior to 9 ma and probably prior to 10 ma assuming a gravelprogradationrateof3cm yr threeapatitefission trackages fromstructuresattheleadingedgeofthemainboundarythrustin the kohat region of northwest pakistan indicate that rapid cooling below 105 c1 2 m y earlier these data indicate that the main boundary thrust in the western himalaya formed synchronously along strike in the middle late miocene has a displacement rate of 10 mm yr and has a displacement history that is coeval with late displacement on the main central thrust

new insights into the origin of two contrasting himalayan granite belts the two parallel belts of miocene granite that extend along much of the himalaya differ in age petrogenesis and emplacement style we suggest that their origin is linked to shear heating on a continuously active decollement that cuts through previously metamorphosed indian supracrustal rocks that were transformed into basement during the initial stages of the indian asian collision numerical simulations assuming a shear stress of 30 mpa indicate that initiation of slip on the himalayan thrust at 24 ma could trigger discontinuous melting reactions leading to formation of the high himalayan granite chain from 24 to 20 ma and the north himalayan belt from 18 to 12 ma this model result agrees well with observation as do model predictions regarding emplacement style and location

badrinath gangotri plutons garhwal india petrological and geochemical evidence for fractionation processes in a high himalayan leucogranite the gangotri leucogranite is the western end of the badrinath granite one of the largest bodies of the high himalayan leucogranite belt hhl it is a typical fine grained tourmaline muscovite biotite leucogranite the petrography shows a lack of restitic phases the inferred crystallization sequence is characterized by the early appearance of plagioclase quartz and biotite and by the late crystallization of the k feldspar this suggests that in spite of being of near minimum melt composition the granite probably had long crystallization or melting interval in agreement with previous experimental studies tourmaline and muscovite have a mainly magmatic origin even though the major element composition is homogeneous there are several geochemical trends when cao decreases there is an increase in na2o rb sn u b f and a decrease in k2o fe2o3 tio2 sr ba zr ree th which are best explained by a fractionation process with early crystallizing phases experimental solubility models for zircon and monazite in felsic melt support a magmatic origin for these two accessory phases as well rb sr isotope data show this granite to have like other hhl heterogeneous isotopic values for sr initial 87sr 86sr ratios calculated at 20 ma range between 0 765 and 0 785 therefore no mixing i e no convection occurred between the different batches of magma in contrast 18o data show little variation 13 04 0 25 implying a source with homogeneous 18o values differences in timing between fluid infiltration and the onset of melting related to differences in temperature of the source could explain why source homogenization occurred for the gangotri and not for the manaslu granite the use of experimental results for solubility and the position of the accessory minerals during melting predict a low viscosity for the melt during its extraction this in turn explains the lack of restitic phases major and accessory in the granite as well as some field features lensoid shape pronounced magmatic layering based on the petrographic and isotopic studies it is suggested that the mechanism of ascent was not diapiric but rather that the melt ascended along several fractures and the level of emplacement was partialy controlled by the density contrast between the melt and host rocks

channel profiles around himalayan river anticlines constraints on their formation from digital elevation model analysis 1 we present a comparison between measured and numerically modeled channel profiles of rivers in two important drainage basins of central nepal the kali gandaki and the arun drainage basins modeled channel profiles are based on a simple stream power approach using best fit exponents defining the nonlinearities in the relative contributions of local channel gradient and water flux to erosion rate our analysis of the stream power in the whole river network confirms the work of other authors that a 50 to 80 km wide zone roughly corresponding to the high himalayan topography is subjected to rapid rock uplift we suggest a model where the uplift of this zone is driven by erosion and isostatic response so that centers of maximum uplift are located within the main channels of the north south draining rivers we also suggest that the rate of uplift slows down with increasing distance to the main channels such a spatial distribution of the uplift leads ultimately to the formation of river anticlines as observed along all major himalayan rivers we propose that the formation of river anticlines along south draining himalayan rivers was accelerated by a sudden increase of the drainage area and discharge when the rivers captured orogen parallel drainages on the north side of the range this may follow successive headward cutting into the tibetan plateau the model is confirmed by differences between main channels and east west running tributaries time dependent numerical models predict that capture events cause strongly elevated erosion rates in the main channel

records of the evolution of the himalayan orogen from in situ th pb ion microprobe dating of monazite eastern nepal and western garhwal abstract in situ th pb monazite ages from rocks collected along two transects the dudh kosi everest eastern nepal and the bhagirathi river garhwal himalaya india perpendicular to the main central thrust mct suggest a striking continuity of tectonic events across the himalaya the youngest age reported in this study 5 9 0 2 ma mswd 0 4 from matrix monazite grains collected beneath the mct in the garhwal region is consistent with several age data from rocks at similar structural levels in central nepal providing support for widespread late miocene mct activity the lateral parallelism of orogenic events is further manifested by the 20 7 0 1 ma age of a high himalayan leucogranite from an injection complex that outcrops along the dudh kosi everest transect resembling ages of these bodies reported elsewhere the youngest monazite grain analyzed along the dudh kosi everest transect is 10 3 0 8 ma the absence of 7 3 ma monazite ages in eastern nepal may reflect a different nappe structure which obscures the reactivated ramp equivalent exposed in the garhwal and central nepal garnets from the mct hanging wall greater himalayan crystallines and footwall lesser himalaya display different major element zoning and the patterns are useful for constraining the location of the thrust system that separates the two lithologies pressure temperature paths for two upper lesser himalayan garnets that contain monazite inclusions indicate the utility of an in situ methodology to constrain the metamorphic evolution of the shear zone along the dudh kosi everest transect upper lesser himalayan monazite grains from three rocks record a clear signal at 14 5 0 1 ma mswd 8 4 and the 23 ma age that characterizes the hanging wall is notably absent monazites collected within a large scale greater himalayan crystallines fold yield the 14 ma age consistent with the structure forming due to mct related compression paleo mesoproterozoic 1407 35 ma matrix monazite grains are found within an augen gneiss unit located beneath the mct whereas cambro ordovician 436 8 548 17 ma inclusions are preserved within garnets of the greater himalayan crystallines the presence of 45 2 2 1 ma grains from lower structural levels of the greater himalayan crystallines indicates the unit realized conditions conducive for monazite growth during the eocene

age of crustal melting emplacement and exhumation history of the shivling leucogranite garhwal himalaya we report a u pb monazite age of 23 0 0 2 ma for the shivling leucogranite a tourmaline muscovite biotite leucogranite at the top of the high himalayan slab in the garhwal himalaya north india the shivling bhagirathi leucogranite is a viscous near minimum melt emplaced as a foliation parallel laccolith via a dyke network not far from its source region prograde heating occurred soon after the india asia collision at c 50 ma up to melting at 23 ma and high temperatures 550 c were maintained for at least 15 ma after garnet growth the leucogranite was emplaced at mid crustal depths along the footwall of the jhala fault a large scale low angle normal fault part of the south tibetan detachment system above kyanite and sillimanite grade gneisses the geometry of the leucogranite laccolith shows biaxial extension and boudinage both perpendicular north northeast south southwest and parallel to the strike west northwest east southeast of the mountain range unroofing occurred by underthrusting beneath the high himalayan slab along the main central thrust zone progressively jacking up the leucogranites removal of material above by low angle normal faulting and erosion very rapid cooling at rates of 200 350 c ma between 23 21 ma immediately followed crystallization as tectonic unroofing and erosion removed 24 28 km of overburden during this time k ar muscovite ages are 22 1 0 ma and fission track ages of zircons from 5000 m on the north ridge of shivling are 14 2 2 1 and 8 8 1 2 ma and apatites are 3 5 0 79 and 2 61 0 23 ma slow steady state cooling at rates of 20 30 c ma from 20 1 ma shows that maximum erosion rates and unroofing of the leucogranite occurred during the early miocene this timing coincides with initiation of low angle north dipping normal faulting along the south tibetan detachment system

granitic magma transport by fracture propagation granitic magmas commonly ascend tens of kilometres from their source terranes to upper crustal emplacement levels or to the earth s surface apart from its obvious bearing on the interpretation of the geology and geochemistry of felsic igneous rocks the magma ascent mechanism critically affects any modelling of the metamorphic evolution of the upper lithosphere as well as its rheology we propose that in general granitic magmas ascend via propagating fractures as dykes in extremely short time periods long distance diapiric transport of granitoid magmas through crustal sections is not viable on thermal or mechanical grounds and there is an apparent total absence of field evidence for diapiric rise of such magmas even in supposed type localities neither the shapes nor internal or external characteristics of granitic plutons necessarily reveal anything about the transport of their precursor magmas these are purely arrival phenomena dictated by local structure kinematics and stress states based on existing numerical treatments of the problem we show that granitic magmas are apparently sufficiently inviscid to travel through fractures to high crustal levels without suffering thermal death by freezing for example a 2000 km3 granitic batholith can be inflated by a 1 km 3m 20 km deep dyke system in less than 900 years the model proposed has numerous far reaching petrological and rheological consequences some of which are outlined

direct measurements of wind stress over the surf zone field data of the wind stress over surf zone waves are presented from an open ocean beach on the east australian coast two ultrasonic anemometers were deployed at nominal heights of 5 and 10 m above the water surface in the intertidal and inner surf zones with concurrent measurements of water levels and offshore wave parameters following a rigorous quality control procedure the wind stress was determined by the eddy correlation technique a constant stress layer was observed between 5 and 10 m elevation considering near neutral conditions only the wind drag coefficients were found to systematically change with the wind angle of approach relative to the shoreline and are much smaller for longshore wind than during onshore wind the concept of an apparent wave steepness changing with wind direction is suggested to explain this behavior the drag coefficients over the surf zone during onshore wind and near neutral conditions were determined to be almost twice the values expected at the same wind speed and open ocean conditions the observed charnock coefficient was similarly an order of magnitude larger than open ocean values a wave celerity of the order of that expected in the inner surf zone is required to explain the observed large roughness and drag coefficients using existing wave age dependent parameterizations this suggests that the slower wave celerity in the surf zone is an important contributor to the increased wind stress in addition to the sawtooth wave shape key points a new field data set of the wind stress over surf zone waves is presented concept of an apparent wave steepness is proposed to explain drag observations surf zone drag coefficients were almost twice the values outside the surf

the detrital record of orogenesis a review of approaches and techniques used in the himalayan sedimentary basins the sediment archive of material eroded from an active tectonic region and stored in adjacent basins can provide a valuable record of hinterland tectonism especially when information in the source region itself is obscured by later metamorphism or removed by tectonism or erosion using the sediment record to document tectonism is a well established approach but more recently there has been a burgeoning of the number of isotopic techniques which can be applied to detrital material in particular single grain analyses thus the scope for application of detrital studies to a number of different tectonic problems has widened considerably in this review the example of sediments eroded from the himalayan orogen and preserved in the suture zone basin foreland basin remnant ocean basins and deep sea fans is used to illustrate the approach techniques as diverse as petrography heavy mineral xrf and sr nd studies single grain dating by ar ar u pb and fission track methodologies and single grain sm nd and pb isotopic analyses are described the paper documents how the sediment record can be used to determine the thermal and tectonic evolution of the orogen constrain mechanisms of continental deformation exhumation rates and palaeodrainage

age of metamorphism in the lesser himalaya and the main central thrust zone garhwal india results of illite crystallinity 40 ar 39 ar fusion and k ar studies

detrital zircon fission track ages from the lower cenozoic sediments nw himalayan foreland basin clues for exhumation and denudation of the himalaya during the india asia collision detrital zircon fission track ft ages from the lower cenozoic sub himalayan foreland basin reflect the progressive effects of crustal thickening and exhumation on the himalayan source rocks as a consequence of the india asia collision the oldest stratum the transgressive marine paleocene eocene subathu formation 57 41 5 ma contains ca 50 ma detrital zircon p1 peak which was derived from the indus tsangpo suture zone and the ladakh batholith of the asian plate a dominant 302 4 21 9 ma peak with a few 520 ma grains in this formation has been derived by erosion of the zircon partial annealing zone zpaz of 240 180 c as the first imprint of the collision this zone affected the himalayan proterozoic basement and its tethyan sedimentary cover since the detritus in the subathu has been derived both from the indian and asian plates the possible suturing of these plates took place during the subathu sedimentation a sudden change in the provenance is recorded in the detrital zircon ft cooling ages in the oligo miocene dagshai and kasauli formations which have dominant 30 and 25 ma p1 peaks respectively we interpret a distinct unconformity spanning 10 m y between the subathu and dagshai formations since ca 30 ma molassic sedimentation coincides with shifting of the source rocks to the himalayan metamorphic belt this belt has sequentially undergone three distinct cooling and exhumation pulses after the ultrahigh pressure high pressure uhp hp metamorphism 53 50 ma in the extreme north and two widespread m1 and m2 metamorphisms 40 30 and 25 15 ma in the middle parts these events appear to be largely responsible for the deposition of the ca 30 ma zircon himalayan peak and ca 25 and 15 ma young himalayan peaks respectively the latter appears within the lower siwalik subgroup 13 11 ma during the lower siwalik deposition pre himalayan peaks gradually decrease with the intensification of the himalayan events in source rocks in spite of uninterrupted fluvial sedimentation in the dagshai kasauli lower siwalik sequences since 30 ma breaks of 5 7 m y in the zircon ft ages reveal pulsative cooling and exhumation in the well identified source areas although cooling and exhumation of the himalayan source rocks remained almost uniform during the eocene source heterogeneity is reflected in fluvial sedimentation since 37 ma from pakistan to nepal in response to the india asia collision

simultaneous miocene extension and shortening in the himalayan orogen the south tibetan detachment system separates the high grade metamorphic core of the himalayan orogen from its weakly metamorphosed suprastructure it is thought to have developed in response to differences in gravitational potential energy produced by crustal thickening across the mountain front geochronologic data from the rongbuk valley north of qomolangma mount everest in southern tibet demonstrate that at least one segment of the detachment system was active between 19 and 22 million years ago an interval characterized by large scale crustal thickening at lower structural levels these data suggest that decoupling between an extending upper crust and a converging lower crust was an important aspect of himalayan tectonics in miocene time

when did the roof collapse late miocene north south extension in the high himalaya revealed by th pb monazite dating of the khula kangri granite th pb ion microprobe measurements made on 12 monazite grains from the khula kangri granite tibet bhutan frontier are interpreted to indicate that crystallization occurred at 12 5 0 4 ma the leucogranite is cut by the gonto la detachment part of the southern tibet detachment system that has allowed upper level north directed extension of the himalayan orogen significant orogen normal extension in southern tibet appears to have continued 8 10 m y later than previously recognized this is the first reported crystallization age for a leucogranite east of the yadong cross structure an apparent 70 km offset of the high himalaya and southern tibet detachment west of the yadong cross structure reliable ages for high himalaya events major main central thrust slip granite generation and emplacement attainment of critical topography and major detachment extension group between ca 24 and 19 ma we interpret the west to east change across the yadong cross structure to be due to either 1 an abrupt 10 m y younging of principal high himalayan events or 2 a deeper thus younger exposed part of the footwall of the southern tibet detachment near khula kangri the southern tibet detachment is cut by the highly oblique yadong gulu rift a manifestation of tibet plateau east west extension integrated estimates of magnitude and rate of detachment displacement suggest that the observed postcrystallization north directed extension lasted for 1 3 m y after which time the yadong gulu rift formed this interpretation is consistent with initiation of east west extension of tibet at ca 8 ma

dating protracted fault activities microstructures microchemistry and geochronology of the vaikrita thrust main central thrust zone garhwal himalaya nw india

thermal model for the zanskar himalaya abstract crustal thickening along the northern margin of the indian plate following the 50 ma collision along the indus suture zone in ladakh caused widespread high temperature medium pressure barrovian facies series metamorphism and anatexis in the zanskar himalaya metamorphic isograds are inverted and structurally telescoped along the main central thrust mct zone at the base of the high himalayan slab along the zanskar valley at the top of the slab isograds are the right way up and are also telescoped along northeast dipping normal faults of the zanskar shear zone zsz which are related to culmination collapse behind the miocene himalayan thrust front between the mct and the zsz a metamorphic anatectic core within sillimanite grade rocks contains abundant leucogranite granite crustal melts of probable himalayan age a thermal model based on a crustal scale cross section across the zanskar himalaya suggests that m1 isograds developed during early himalayan barrovian metamorphism were overprinted during high grade mct related anatexis and folded around a large scale recumbent fold developed in the hanging wall of the mct

kinematic model for the main central thrust in nepal comment and reply comment in the main central thrust zone of the central nepalese himalaya monazites decrease in age downsection between the main central thrust and main central thrust 1 mct 1 in fig 1 1 from ca 22 to 3 3 ma catlos et al 2001 2 this astonishingly systematic result kohn et al 2001 3 has

pressure temperature and time constraints on himalayan metamorphism from eastern kashmir and western zanskar himalayan metamorphism in the kashmir and zanskar sector of the high himalaya resulted from thrust and fold related crustal thickening within the indian plate following the collision of india and asia at c 50 ma interbanded metapelites marbles calcareous schists amphibolites and quartzites represent metamorphosed equivalents of the palaeozoic lower mesozoic continental margin rocks granitic rocks include pre collision k feldspar megacrystic and biotite granites and post collision two mica garnet tourmaline granites average pressure temperature conditions of equilibration using the self consistent thermodynamic data set of holland powell 1990 are presented across a 45 km traverse of the eastern kashmir western zanskar high himalaya kyanite is the stable aluminosilicate phase across 35 km outcrop width in the middle of the slab complex microstructures indicate that prograde metamorphism up to kyanite grade and fabric development in the upper structural nappes is early and unrelated to the main central thrust diachronous metamorphism propagated southwards with the overall structural evolution early isograds and thrust fold structures were carried passively in the hanging wall of the main central thrust peak metamorphism based on 40 ar 39 ar hornblende ages occurred pre 30 7 2 0 ma at the top of the slab and in the middle of the slab was pre 22 1 0 ma probably 25 28 ma the lower structural levels in zanskar record peak metamorphic conditions around 700 750 c and 8 kbar reflecting depths of burial of 28 30 km a new younger schistosity which is not present in the higher structural levels was developed under kyanite grade conditions the regional distribution of high temperatures recorded by thermo barometry does not support the concept of additional heat being supplied by frictional heating along the main central thrust or magmatic heat resulting from anatexis exhumation of the himalayan metamorphic rocks was achieved by three major processes erosion as a result of crustal thickening uplift of the rocks along the hangingwall of the main central thrust above a major frontal ramp in the kishtwar window area and extensional unroofing along the footwall of a large scale ne dipping normal fault at upper crustal levels probably synchronous with compression at depth

tectonic evolution of the central annapurna range nepalese himalayas the metamorphic core of the himalayan orogen or greater himalayan sequence is a northward tapering prism bound at the bottom by a n dipping family of thrust faults the main central thrust system and at the top by a n dipping family of normal faults the south tibetan detachment system research in the central annapurna range of nepal demonstrates a close temporal and spatial association between contractional and extensional deformation on these bounding fault systems and within the metamorphic core throughout much of the early miocene the main central thrust system is represented here by a 2 to 3 km thick zone of high strain that developed during two or more episodes of movement most of its displacement was concentrated along the chomrong thrust a sharp late metamorphic discontinuity that places middle amphibolite facies rocks of the greater himalayan sequence on top of lower amphibolite facies rocks of the lesser himalayan sequence the earliest demonstrable movement on this thrust system occurred 22 5 ma the most recent movement may be as young as pliocene the oldest element of the south tibetan detachment system in this area is the deorali detachment which appears to have been active at the same time as the earliest shortening structures of the main central thrust system fabrics related to the deorali detachment are disrupted by a previously unrecognized sw vergent thrust structure the modi khola shear zone the effect of this structure which is constrained to be between 22 5 and 18 5 ma was to shorten rock packages that had been extended previously during movement on the deorali detachment transition back to a local extensional regime after 18 5 ma was marked by development of the machhupuchhare detachment and related splays geologic evidence for rapid two way transitions between contraction and extension in the annapurna range indicates that extensional deformation in convergent settings does not only represent gravitational collapse at the end of an orogenic cycle it also appears to be an important factor in mountain range development

mid eocene high sr y granites in the northern himalayan gneiss domes melting thickened lower continental crust abstract within the himalayan collisional belt granotoids occur along two sub parallel belts the northern himalayan gneiss domes nhgd and the high himalayan crystalline series hhcs in the yardoi area of nhgd two mica granite a new type granite occurs in the core of the yardoi gneiss dome ygd dala and quedang from north to south and extends at least 50 km long these granites have similar mineral composition elemental and radiogenic isotope geochemistry and age of formation shrimp zircon u pb dating indicates that the yardoi and the quedang two mica granites formed at 42 6 1 1 ma and 42 8 0 6 ma respectively similar to the dala pluton these two mica granites have 1 high sio2 68 wt al2o3 15 wt and a cnk 1 0 2 relatively high sr and lree but low y 40 and up to 250 and la yb 30 4 very weak or no eu anomalies and 5 as compared with those in the himalayan leucogranites low initial sr 87sr 86sr i

defining local signature in terms of sr isotope composition using a tenth to twelfth century anglo saxon population living on a jurassic clay carbonate terrain rutland uk abstract the sr isotope ratios mad sr concentration in tooth enamel from a rural tenth twelfth century anglo saxon population living on a jurassic clay carbonate terrain in eastern england gives the following mean values 87sr 86sr 0 709820 0018 2o n 22 and sr concentrations 74 62 p p m 2o the isotope data are taken to be representative of anglo saxon biosphere values in the area of study the sr isotope composition of soil leachates plant material riverwaters and animal tooth enamel associated with the burial site were all analysed to see which gave the best approximation to these local anglo saxon values the aim being to define the best method of predict ing the local sr signature of areas for archaeological purposes the sr isotope composition of acetic acid soil leachates were dominated by the carbonate soil component and gave 0 7085 2 0 0020 water leachates gave 0 7090 0 0014 and plant material gave 0 7092 0 0018 all at 2o n 12 all of these materials were less radiogenic that those of the anglo saxon population riverwater gave the same result as the plants at 0 7092 2 0 00 2 2o n 3 the anglo saxon animal tooth enamel gave the best match with a value of 0 7099 0 0017 2o n 13 analysis of variance anova tests show that there is a high probability 70 probability 2sd that the animals and the humans sampled were from the same population with respect to sr isotope composition thus animal tooth enamel proved to be the best proxy in this study for the local human population many archaeological studies use skeletal sr isotope characteristics in an attempt to determine whether a group of people comprise a single population whether there is an exotic component in the group or whether or not the entire group come from outside the area in question price