chronology of late wisconsinan glaciation in middle north america abstract we propose a chronology of late wisconsinan glacial fluctuations in middle north america from alberta to wisconsin based on radiocarbon dates derived solely from wood previous chronologies of the southwestern margin of the north american continental ice sheet have depended to a considerable degree on radiocarbon dates from fine grained organic sediment this material is commonly contaminated with older carbon resulting in chronologic confusion by using only dates from wood much of the confusion disappears however because of the scarcity of wood dates only four of the sixteen identified fluctuations are accurately dated an advance into iowa about 14 000 to 13 500 bp an advance into south dakota and iowa about 12 300 bp an advance into the lake michigan basin about 11 700 bp and an advance into the lake superior basin about 9900 bp in addition the beginning of late wisconsinan glaciation before 20 000 bp is fairly well documented none of the fluctuations in the western part of the region are accurately dated

radiocarbon dating of marine shell samples the marine radiocarbon reservoir effect of coastal waters off atlantic iberia during late neolithic and chalcolithic periods abstract radiocarbon dates on marine shells have not been used as extensively as charcoal or bone dates for the setting up of absolute chronologies because interpreting these dates is complicated by the marine radiocarbon reservoir effect nevertheless marine shellfish were used widely at least during the holocene and their shells are abundant and usually well preserved in archaeological deposits located near shorelines consequently prior research concerning the oceanographic conditions and the marine radiocarbon reservoir effect of a particular coastal area is needed in order to set up reliable chronologies for that region values of regional marine radiocarbon reservoir effect r of coastal waters off atlantic iberia some of its variability along the holocene and its correlation with the upwelling phenomenon were determined during previous research more data related to the r values for western portuguese coastal waters during the late neolithic and the chalcolithic a time interval badly sampled in previous research were recently obtained these values can be compared with r values already determined for the gulf of cadiz besides the importance of these values for a better knowledge of the palaeoceanography and palaeoclimatology of atlantic iberia from now on archaeologists can set up reliable chronologies for late neolithic and chalcolithic contexts using marine shell samples of that origin for radiocarbon dating

late quaternary events in the lethbridge area alberta new observations in the lethbridge area permit a more complete reconstruction of the landscape history in late wisconsinan and holocene time the plain of glacial lake macleod the lethbridge moraine and the plain of glacial lake lethbridge became exposed in that order and in quick succession almost immediately thereafter a discontinuous mantle of loess began to accumulate on those surfaces the presence of glacier peak layer g or manyberries tephra near the base of the loess indicates these events occurred just before 11 200 bp the similarity of this chronology to that established for the older green lake end moraine in the cypress hills region and the fact that the younger buffalo lake moraine was formed before 11 000 bp indicate that deglaciation of southern alberta proceeded very rapidly the oldest buried paleosol observed near lethbridge began to form shortly after 11 200 bp subsequently and throughout the holocene intervals of loess deposition alternated with soil forming intervals at least

geo archaeological evidence for a holocene extreme flooding event within the arabian sea ras al hadd oman abstract the arabian sea is regarded as one of the least studied regions in terms of coastal hazards such as tropical cyclones and tsunamis parts of the coastline are developing rapidly especially in oman this calls for a proper understanding of the natural processes that act on and affect it this can be done by investigating the magnitude and impact of past events in particular on human settlements by doing this future risks may not only be scientifically predicted and evaluated but the damage caused by future events might even be mitigated evidence of past extreme wave events is preserved in the onshore stratigraphic record in addition to this the coastal zone of oman is rich in archaeological remains presented here are the results of comprehensive mapping and analysis of extreme wave deposits of an archaeological site near ras al hadd suggesting that the early bronze age site hd 6 was inundated at 4450 cal bp an event layer is identified between two settlement phases within the archaeological excavation a contemporaneous sand bed with a maximum thickness of 0 4 m was mapped in the vicinity of the settlement ground penetrating radar surveys allow measurement of the thickness as well as identification of the internal facies architecture of the deposit a high resolution digital elevation model reveals the coastal geomorphology it is concluded that the causative event must have been a tsunami that was most likely generated within the makran subduction zone this interpretation does however remain tentative at the moment archaeological evidence indicates that the site was immediately re occupied after the event which attests to a certain resiliences of the early bronze age coastal communities in the region

variability in the marine radiocarbon reservoir effect in muscat sultanate of oman during the 4th millennium bc reflection of taphonomy or environment abstract radiocarbon 14 c dating of archaeological coastal sites in arid areas is challenging because of the relative rarity of datable terrestrial artefacts marine artefacts provide an abundant source of carbon which is technically easy to date but radiocarbon dates need to be corrected for local variations from the global average marine 14 c reservoir age r in archaeological sites this is usually done by the comparison of the 14 c age measured between coeval pairs of terrestrial and marine samples that have no inbuilt age here we present the results of a study that aims to determine the local 14 c marine reservoir effect mre along the eastern coast of the arabic peninsula during the 4th millennium bc a period of important cultural demographic and social changes in this region previous estimates of the mre based on associated shells and charcoal vary by about 400 14 c yr and this is a serious limitation to the establishment of a precise chronology in the area based on marine material in order to maximize the chances to obtain contemporaneous terrestrial marine pairs for a new assessment of the mre in this region we dated charcoal shells fish and turtle bones as well as human bones found in three recently and carefully excavated graves from ra s al hamra rh5 a large variability was found between charcoals up to 240 14 c yr and marine specimens up to 785 14 c yr present in the same grave this variability was attributed to inbuilt ages diagenesis and possibly environmental factors although taphonomic processes cannot be excluded we discarded the oldest charcoals and used the 14 c ages obtained on human apatite as a cut off value to remove the marine outliers two out of the three graves provided terrestrial and marine assemblages which did not differ statistically and were used to calculate an average mre of 645 40 14 c yr r 255 55 14 c yr this value is consistent with previous estimates based on the 14 c dating of marine sediments off pakistan and suggests stability of the mre in the arabian sea since the 4 th millennium bc

characteristics of sediment profiles in reservoirs abstract published data for sediment profiles in the harry strunk guernsey elephant butte and lake mead reservoirs u s a are analyzed it is shown that the profiles can be described by the equation y axb where x and y are horizontal and vertical distances respectively from the pivot point this equation can be used to determine the slope of the profile at any specified point and to determine the location of the transition point between the foreset and bottomset beds correlations are given which permit an estimate of the longitudinal and vertical extent and the shape of the topset foreset and bottomset components of the sediments this information can be used to predict the complete sediment profile in a reservoir provided that the horizontal distance of the pivot point from the dam is known or estimated

south asian monsoon climate change and radiocarbon in the arabian sea during early and middle holocene the 1 4 c ages of planktonic foraminifers globigerinoides sacculifer bracketing the younger dryas in a 1 8 o record of globigerinoides ruber from a laminated sediment core on the pakistani continental margin suggest thatsurface reservoir ages in the arabian sea were in excess of 1000 years during the deglaciation a least squares error fit of a detailed 1 4 c chronology to the atmospheric tree ring record gave variable early holocene reservoir ages between 780 and 1120 years well above the prebomb value of 640 years mid holocene reservoir ages are less well constrained but were probably closer to the prebomb value the method used to fit individual core sections to the tree ring record was designed to require only a rough a priori estimate of the time spans which in the core presented here were taken from each section s range of 1 4 c ages a significant 220 year quasi oscillation was present in the 1 8 o record during the early holocene but not thereafter this frequency and amplitude pattern resembles an early holocene 207 to 227 year oscillation previously observed in the atmospheric 1 4 c record which is generally interpreted as reflecting solar irradiance variability an early holocene climate event at 8150 8400 calendar years b p observed elsewhere within the asian east african monsoon system was again found in our record suggesting a reduction in precipitation over nw india and pakistan

evidence for temporal fluctuations in marine radiocarbon reservoir ages in the santa barbara channel southern california abstract differences in the 14 c ages of closely associated marine shell and carbonized plant material from stratified archaeological deposits on san miguel island california suggest holocene 10 000 present fluctuations in marine 14 c reservoir ages these fluctuations coincide with 18 o and 13 c shifts measured in mytilus californianus shells from the same stratigraphic contexts and general atmospheric oceanic circulation models for the region based on these data we make three primary observations 1 significant changes appear to have occurred in the radiocarbon reservoir during the holocene 2 these fluctuations appear to correlate with regional oceanographic changes and 3 high resolution 14 c dating of marine shells may require different r values for different periods of time

pleistocene stratigraphy of the saskatoon area saskatchewan canada an update pleistocene deposits in the saskatoon area are divided into the sutherland and saskatoon groups the sutherland group is divided into the mennon dundurn and warman formations and the saskatoon group is divided into the floral and battleford formations the floral formation is subdivided into the lower till the riddell member and the upper till each formation is composed of a sequence of deposits including basal proglacial sediment till upper proglacial sediment and nonglacial sediment each formation is defined primarily on the basis of carbonate content and stratigraphic position of its till and commonly it is bounded by weathered zones and or nonglacial sediments the sutherland group is pre illinoian in age and the lower till of the floral formation is illinoian in age the riddell member between the lower and upper tills of the floral formation is late rancholabrean probably sangamon in age radiocarbon ages of sediments lying between the upper till of the floral formation early wis

profiles of modern prograding deltas surface profiles of a tailings delta and several modern prograding river deltas are described by the equation y axb where x and y are horizontal and vertical distances respectively from the edge of the delta lip this relationship is used to determine the slope of a profile at any specified point and to determine the location of the transition point between foreset and bottomset beds a dimensionless equation of the form y xb is used to compare the shapes of different deltas the exponent b has an average value of about 0 5 and 0 9 for lake and ocean deltas respectively the depth of the water in the receiving basin is a key factor that influences the shape of the foreset beds the shape of the profile for foreset beds of lake deltas can be closely predicted by y kx0 533 where k is a coefficient that correlates with the maximum depth of water ymax in the lake near the delta front for ocean deltas where ymax is undefined k must be correlated with some other reference parameter such as y1 w

a reconstruction of holocene geomorphology and climate western cypress hills alberta and saskatchewan received january 28 1990 revision accepted july 18 1990 the cypress hills of southwestern saskatchewan and southeastern alberta are a key area for quaternary research because the permanent lakes and coniferous forest are sources of proxy paleoenvironmental data generally not available on the surrounding northern great plains in this paper the holocene paleoclimate of the western cypress hills is reconstructed from the pollen and organic matter contents of a 9 6 m sediment core from harris lake saskatchewan this climatic history is considerably longer than others from the semiarid interior plains of canada chronological control consists of a basal conventional radiocarbon date of 9120

late wisconsinan and holocene history of southwestern saskatchewan the late wisconsinan laurentide ice sheet reached the limit of glaciation along the north facing slope of the unglaciated part of the cypress hills nunatak but elsewhere around the cypress hills and wood mountain uplands of southwestern saskatchewan it did not reach the limit of glaciation an interval of deglaciation was followed by a readvance of the ice sheet about 15 ka to a position near the late wisconsinan limit and was marked by strong flow of keewatin ice from the north and weaker flow of hudson ice from the northeast final deglaciation resulted in the formation of glacial lakes around the cypress hills nunatak a network of ice marginal and subglacial trenches presently occupied by the frenchman valley and its tributaries was formed when these lakes drained along over and under ice towards the western part of the wood mountain upland to the east the main trench joined an ancestral part of frenchman valley along the ice free southern slopes of wood mountain upland meltwater from the ic

stratigraphy of the north cliff section wellsch valley site saskatchewan eight separate till sheets are displayed at the north cliff which is part of the wellsch valley site in saskatchewan those tills are differentiated by using physical characteristics particle size clay and primary mineralogy and sediment chemistry grain size tends to fine downward in the section and a significant increase in the mean 4 centre of gravity indicates that some weathering occurred after deposition of the tills within the clay mineral suites smectite tends to dominate in all eight tills indicating that the paleoclimate was generally as dry as the present day climate only till number 4 counting from the bottom contains halloysite this halloysite may have been entrained from a preweathered surface by the glacier or it may have formed in situ following deposition among the primary minerals quartz dominates throughout the section whereas plagioclases are least abundant in tills 4 and 5 possibly as a result of postdepositional weathering element composition shows only minor changes for cu pb zn co and ni whereas mo increases upward in the section cr remains uniform in tills 1 2 3 7 and 8 but increases slightly in tills 4 6 and mn increases downward possibly as a response to fluctuating amounts of groundwater till 4 forms the best stratigraphic marker in the sequence because of its high mn content and the presence of halloysite but till 5 also contains distinctive features in its element composition the clay composition of the surface soil which has formed in the top till since the departure of the last glacier resembles that found in the underlying tills whereas quartz and plagioclase are present in lesser amounts these properties reflect both weathering in a semiarid climate and the presence of preweathered material from earlier paleosols

a holocene soil geomorphic record from the ham site near frontier southwestern saskatchewan the soil geomorphic evolution of a hillslope in hummocky moraine terrain in one of the most arid parts of the palliser triangle is reconstructed from ca 12 600 bp to the present a transect from a moraine plateau into an internally drained basin provided evidence for seven postglacial landscape cycles each cycle includes a phase of land surface instability marked by erosional and depositional imprints and a phase of stability marked by pedologic imprints five cycles of slope wash dominated erosion left behind four superposed downslope thickening and downslope fining sediment mantles and were followed by two eolian cycles each of which left behind a loess mantle that accumulated from a local loess dispersal system accumulation of long range calcareous dust coincided with each of these loess cycles the five complete buried soil catenas and the surficial catena have systematic textural differentiation reflecting the preceding geomorphic regimen and color differentiation reflecting the soil draina

conjunctive use of deterministic and stochastic models for predicting sediment storage in large reservoirs 1 a stochastic sediment storage model abstract the papers presented discuss the development of a model to predict the deposition of sediment in reservoirs as a function of time in years the papers consist of three parts which are published together the present paper part 1 deals with the development of a stochastic model for the total deposition of sediment in reservoirs this cumulative deposition of sediment in time is shown to be an additive process defined on a finite markov chain the model is analysed to obtain the mean and the range of the cumulative deposition as a function of discrete time in years part 2 discusses a deterministic model for the deposition process along the length of the reservoir the pattern of deposition is shown to be a function of the inflow and the concentration of sediment in the inflow as well as the initial level in the reservoir and the initial composition of sediment the inflow in the reservoir is treated as unsteady and non uniform as much of the physical characteristics of the reservoir as possible is included in the analysis part 3 discusses the application of the two models in conjunction to the john martin reservoir bent county colorado for which measurements are available though limited in extent the comparison between results obtained from the model and the actual measured data is found to be in good agreement with each other the symbols used and references are provided separately in the notation and references section of each part

abrupt changes in the asian southwest monsoon during the holocene and their links to the north atlantic ocean during the last ice age the indian ocean southwest monsoon exhibited abrupt changes that were closely correlated with millennial scale climate events in the north atlantic region1 2 3 suggesting a mechanistic link in the holocene epoch which had a more stable climate the amplitude of abrupt changes in north atlantic climate was much smaller and it has been unclear whether these changes are related to monsoon variability here we present a continuous record of centennial scale monsoon variability throughout the holocene from rapidly accumulating and minimally bioturbated sediments in the anoxic arabian sea our monsoon proxy record reveals several intervals of weak summer monsoon that coincide with cold periods documented in the north atlantic region4 including the most recent climate changes from the medieval warm period to the little ice age and then to the present we therefore suggest that the link between north atlantic climate and the asian monsoon is a persistent aspect of global climate

application of till pebble lithology to the differentiation of glacial lobes in southern alberta variations in the pebble composition of surface till in southern alberta indicate the presence of three contemporaneous lobes in the last continental glacier the ice lobe domains have similar pebble associations and differ only in the frequency of occurrence of rock constituents a large part of the percentage variability within each domain is caused by irregular entrainment of locally derived stones which dilutes pebble contents and results in a lithology substantially different from the provenance composition the study has shown that the regional trends are preserved and can be recognized in the locally modified lithologies but the latter have to be isolated and evaluated differently from the regular provenance lithologies the common diluting agent in the area is fluvial gravel that is widespread on erosional bedrock surfaces and in preglacial valleys because the gravel is generally coarse pebble fractions of larger size are more affected by local dilution than are successively finer fractions q

radiocarbon dating of biological apatites a review abstract since the early trials in the 50 s the reliability of 14c dates obtained from bioapatites has always been questioned however methodological attempts at dating biological apatites are rare the compilation of the radiocarbon dates published in radiocarbon over the period 1959 2009 shows that less than 6 of all the bone dates were performed on purified bioapatite crucial for the validation of the approach is the design of tests for the preservation of the geochemical signal in biological apatites that are relevant for 14c dating because carbonate in apatite can exchange isotopically with dissolved carbon present in the environmental fluids pretreatments are necessary but not sufficient and preservation criteria based on mineral integrity are of limited help in this case only an indirect approach based on the dating of different bone tooth fractions of the same individual and or associated material is able to distinguish between preserved and altered fossils in case of alteration it is unlikely that the rate of isotopic exchange recrystallization will be identical in skeletal tissues with different physico chemical properties and any intra individual difference measured in 14c age must result from differential diagenesis we applied this strategy to more than 100 holocene and late pleistocene localities worldwide this approach confirms that carbonate in calcined bone is very resistant to post burial isotopic exchange and is the most reliable source of inorganic carbon for 14c dating regardless of the environmental conditions large intra individual differences in 14c age are found in several european and american localities showing that both bone and enamel apatite can suffer from rejuvenation due to isotopic exchange during fossilization on the contrary the absence of significant intra individual differences in 14c age in most of the localities from arid environments africa arabic peninsula attests to the good preservation of bone apatite in these regions this contrasting situation confirms that bone diagenesis must be treated on a site by site basis and demonstrates that bioapatite is a reliable material to date skeletal remains in arid environments

stratigraphy and paleomagnetism of late pliocene and pleistocene sediments in the wellsch valley and swift current creek areas southwestern saskatchewan canada the late pliocene and pleistocene are represented in southern saskatchewan by sequences of preglacial glacial and nonglacial deposits these have been studied in surface exposures and bore cores and have been subdivided and correlated on the basis of their lithologies in this study new observations of magnetic polarity are presented they reveal a lower preglacial sequence empress group with reversed polarity and an upper normally magnetized sequence which contains glacial deposits of pre illinoian illinoian and wisconsinan age and which are correlative with the saskatoon and sutherland groups of central saskatchewan the reversed preglacial sequence is referred to the matuyama zone late pliocene to early pleistocene 2 58 0 78 ma and the normal glacial sequence to the brunhes zone middle to late pleistocene and holocene 0 78 ma to present in southern saskatchewan there is no evidence of glaciation during the late pliocene and early pleistocene matuyama chron which is in marked contrast w