dating the quaternary progress in luminescence dating of sediments abstract luminescence dating comprises a collection of numerical age techniques that are among the most significant chronological tools currently used in quaternary research this paper briefly reviews the key historical developments in luminescence dating from its roots in thermoluminescence dating of heated minerals to the development of optical dating methods for sunlight exposed sediments we describe the principles and practicalities of the various techniques commonly used in luminescence dating including multiple aliquot single aliquot and single grain procedures and we discuss some of the latest approaches to recognising and minimising potential errors in age estimation e g by means of component analysis and dose distribution methods in optical dating the overview also introduces the other papers in this special issue of quaternary science reviews which address a selection of important issues in basic research technique development and application of luminescence dating to critical questions in the geological and archaeological sciences illustrated with examples from around the world and the last million years of earth history

sediment transport by dry ravel 1 dry ravel is a general term that describes the rolling bouncing and sliding of individual particles down a slope and is a dominant hillslope sediment transport process in steep arid and semiarid landscapes during fires particles can be mobilized by the collapse of sediment wedges that have accumulated behind vegetation on a daily basis particles may be mobilized by bioturbation and by small landslides experiments on a dry ravel flume indicate that a basic expression of the momentum equation predicts the distance traveled by particles propelled down a rough surface this equation is further elaborated to produce a nonlinear slope dependent transport equation for dry ravel that represents the rate at which sediment crosses a contour width of slope sediment traps installed on two hillslope transects near santa barbara california measured the flux from dry ravel initiated by bioturbation and the data support the form of the equation additionally a physical model based on the infinite slope stability analysis is proposed for the initiation of dry ravel by landsliding the analytical result from this model is supported by experiments and field data reported by others

a 43 000 year vegetation and fire history from lake baraba new south wales australia abstract palaeoenvironmental sequences that describe the vegetation of the last glacial maximum lgm and of the subsequent climatic amelioration are relatively rare in the australian southeast asian and pacific region seapac region here we present the results of a palynological investigation from lake baraba located in eastern australia which extends beyond 43 ka bands of oxidised sediment prior to the lgm suggest lake level fluctuations however lacustrine clays continued to be deposited throughout the lgm and into the early holocene when the deposition of peat was initiated the vegetation a casuarina woodland shrubland with a mixed understorey remained relatively stable from 43 kyr to the early holocene suggesting that this sclerophyllous vegetation was resilient to changes in climate the vegetation of the lgm at lake baraba does not conform to previous descriptions of a treeless south eastern australia and it is possible that it was a refugium for woodland myrtaceae expanded at the expense of casuarinaceae from the early holocene with charcoal analyses suggesting that fire was an unlikely explanation there was no apparent relationship between aboriginal site usage and fire activity and hence how aboriginal people used fire at lake baraba remains speculative

the character and age structure of valley fills in upper wolumla creek catchment south coast new south wales australia extensive valley fills at the base of the escarpment in upper wolumla creek on the south coast of new south wales australia have formed from a combination of cut and fill processes the valley fills comprise series of alternating horizontally bedded sand and mud units reflecting reworking of detritus from deeply weathered granites of the bega batholith sand units are deposited as sand sheets or splays on floodplain surfaces or in floodouts that form atop intact valley fill surfaces downstream of discontinuous gullies alternatively sands are deposited from bedload and form bars or part of the valley floor within channel fills organic rich mud units are deposited from suspension in swamps or in seepage zones at the distal margin of floodouts within 5 km of the escarpment valley deposits grade downstream from sand sheet and splay deposition in floodouts to mud deposition in swamp and seepage zones radiocarbon dates indicate that virtually the entire valley fill of upper wolumla creek was excavated prior to 6000 years bp remnant terraces are evident at valley margins the valley subsequently filled between 6000 years bp and 1000 years bp producing valley fills around 12 m deep but no greater than 300 m wide reincision into the valley fill on a scale smaller than the present incision phase is indicated at around 1000 years bp following which the channel refilled portion plans dated from 1865 refer to the study area as wolumla big flat and show large areas of swampy terrain suggesting that the valley fill had re established by this time within a few decades of european settlement the valley fill incised once more upper wolumla creek now has a channel over 10 m deep and 100 m wide in places draining a catchment area of less than 20 km2 1998 john wiley sons ltd

shear wave splitting and anisotropy in the charlevoix seismic zone quebec during the month of august 1984 an experiment was undertaken in the charlevoix seismic zone to test the hypothesis that shear wave splitting could be observed in a seismically active region seismograms recorded by digital 3 component seismographs located very close to the epicentres of three earthquakes showed shear wave splitting the amount of splitting was estimated to be 1 6 to 2 of the shear wave velocity from particle motion diagrams the average azimuth of the direction of polarization was 30 these observations can be explained by the presence of vertical cracks striking 30 east of north with a minimum crack density of e 0 03

evolution of overland flow after a severe forest fire point reyes california abstract forest fires on granitic soils often increase overland flow and erosion runoff generation was monitored on a small hillslope plot on mt vision near point reyes peninsula california after it had been burned by a wildfire on october 3 1995 after the fire the ground surface was covered with up to 2 cm of ash which overlaid a 5 20 cm thick hydrophobic water repellent soil layer we used nine recording tensiometers to monitor soil water potentials during infiltration and runoff surface runoff rates were determined by diverting the flow into a collection tank the subsurface flow through the upper 6 cm of soil was collected and measured in a second tank the surface runoff was diverted to a tank in order to record its rate the initial intense rainfall infiltrated into the base of the ash bed here the hydrophobicity limited deeper penetration and led to both subsurface and shallow saturation overland flow the preferential flow paths through the ash layer contributed to deeper water penetration as the ash was eroded and consolidated with successive rainstorms the preferential flow paths clogged the infiltration capacity reduced thus preventing the storage of shallow permeable soil therefore the runoff generation changed to hortonian overland flow correspondingly the runoff ratio increased from approximately 0 2 during the early storms to 0 8 during intense rain bursts these results suggest that runoff mechanisms evolve simultaneously with the eroding soil surface

microseismicity in the mid st lawrence valley charlevoix zone quebec abstract previous seismicity studies of the charlevoix zone of the mid st lawrence valley have defined the extent of the active zone continued monitoring of this zone has yielded more hypocenters that together with the previous data give a more detailed picture of the hypocentral distribution of the microactivity a more definite correlation can now be made with the known structure in this region and the faults of the st lawrence valley in general the cumulative data permit a definition of lateral boundaries of the seismic activity range of focal depths and anomalous nonseismic zones it is also possible to make a correlation with the normal faults that were probably associated with the paleorifting of the st lawrence valley but are now under compression in this seismically active region part of these preexisting partially sealed faults were most likely weakened again at the time of formation of the charlevoix impact structure

seismicity and faulting in the charlevoix zone of the st lawrence valley abstract continuous monitoring of the seismically active charlevoix zone since late 1977 has delineated the boundaries of the earthquake zone under the north shore and has enabled an association to be made with surface mapped faults that strike along the st lawrence valley and dip to the southeast within the active zone aseismic volumes are found under parts of the st lawrence river and another elongated zone of activity is found to the southeast on unmapped faults dipping under the river the previous suggestions that the activity is related to old rift faults which have been later weakened by a meteor impact would seem to be upheld

a three dimensional p wave velocity model for the charlevoix seismic zone quebec canada 1 a three dimensional p wave velocity model has been developed for the charlevoix seismic zone csz the csz is located along the st lawrence river 100 km northeast of quebec city canada and is one of the most active seismic zones in eastern north america five earthquakes with magnitudes equal to or exceeding 6 0 have occurred in the csz in historic time and around 200 earthquakes occur annually hypocenters are located in precambrian basement rocks basement rocks have been affected by numerous tectonic events including grenvillian collision iapetan rifting and meteor impact we performed a sequential tomographic inversion for p wave velocity structure based upon 3093 p wave arrivals from 489 earthquakes recorded by 12 stations high velocity is associated with the center of the impact crater the region of high velocity is surrounded by low velocities interpreted to be highly disrupted rocks an elongated high velocity region is present at midcrustal depths that trends parallel to the st lawrence river earthquakes avoid the high velocity body and separate into two bands one on either side of the feature larger earthquakes magnitude 4 have occurred along the northern edges of the high velocity region

progress towards single grain optical dating of fossil mud wasp nests and associated rock art in northern australia here we report on investigations into optical dating of fossil mud wasp nests as a means of constraining the ages of overlying and underlying rock paintings in northern australia we describe the application of a dual signal regenerative dose approach using the easy to bleach fast and hard to bleach slow components of optically stimulated luminescence osl emitted by individual sand sized grains of quartz extracted from two nests a modern nest 2 yr old and a nest dated by 14c to about 30 000 calendar years 30 ka for the modern nest most of the palaeodoses obtained from both the fast and slow components are consistent with a zero age while the 14c dated nest yielded an age of 27 1 1 5 ka from those grains that yielded concordant palaeodoses from the fast and slow components as measured by linearly modulated osl our findings indicate that a dual signal approach permits grains that were fully bleached by sunlight at the time of nest construction and that have since remained concealed in the light safe core of a nest to be distinguished from a grains that were incompletely bleached before nest construction and b grains embedded in the continuously light exposed exterior portion of a nest we conclude that reliable optical ages for small mud wasp nests associated with ancient rock art may be obtained using the dual signal approach and the light safe grains

upper crustal stresses and vertical stress migration in eastern canada diversified phenomena are contributing to our knowledge of various aspects of the stress field and the origin of the crustal stresses in eastern canada both in situ stress measurements to 2100 m and earthquake fault plane solutions in the upper crust 5 20 km indicate that the maximum horizontal stress is greater than the vertical absence of earthquakes in the lower crust 20 km implies a comparatively lower deviatoric horizontal stress in this layer stress directions as determined from both in situ measurements and earthquake fault plane solutions indicate an overprint confined to the ene octant which correlates with the direction predicted by modeling of plate tectonic stresses thus spreading mid atlantic ridge stress is considered to be one of the important contributors to the stress field in eastern canada viscoelastic relaxation of this stress is considered to enhance the deviatoric stress level in the upper crust while simultaneously reducing that in the lower crust the crust acts as a stress guide within which stresses in the upper crust that are lost through brittle failure i e earthquake stress drop can be replenished from the lower crust moreover the directionality predicted by modeling of spreading mid atlantic ridge stress is maintained incomplete postglacial rebound also contributes to deviatoric compression other possible contributors to the upper crustal stress field are basal drag and membrane stress but the relative contributions from these sources are not properly understood

p wave deflection or off azimuth arrivals in the charlevoix seismic zone abstract during the months of august 1984 and october 1985 experiments were undertaken in the charlevoix seismic zone to record high frequency body waves from earthquakes the seismograms were recorded by digital three component seismographs the experiments were conducted on the north shore of the st lawrence river only and covered nine sites all but the two most northeasterly recording sites exhibited p wave arrivals that arrived from azimuths that differed from the theoretical azimuth based on the computed hypocenter station relationship these differences amounted to several tens of degrees neither the errors in hypocenter location nor in the orientation of the horizontal seismometers are believed to be the cause of this difference theoretical computations based on a two dimensional model with strong lateral velocity gradients or a discontinuity in velocity produce deviations of the direction of arrival of the p wave in a horizontal plane normal to the anomaly that can amount to several tens of degrees both the lateral gradient and discontinuity models satisfy the observed deviation of azimuth versus azimuth deflection however only the discontinuity satisfies the deflection versus hypocentral distance distribution at least for distances to 20 km comparing the observed data with the theoretical values suggests that the anomaly in velocity occurs in a near vertical plane striking parallel to the st lawrence river this is also the direction of ancient extension faults in the region other structures were introduced 350 m y ago when the charlevoix impact structure was formed a number of anorthosite bodies with very high seismic velocities also outcrop in the region because of the high frequencies involved the scale of the anomaly may well be only a few hundred meters and the anomaly may most likely be located very close to even directly beneath the station

nontidal tilt and water table variations in a seismically active region in quebec canada abstract an array of three borehole tiltmeters was installed in 1981 in the charlevoix region of quebec canada an area of high intraplate seismic activity a magnitude 7 0 earthquake struck the area in 1925 and the last major event was a magnitude 5 0 event which occurred in 1979 the nontidal tilt from two 47 m deep boreholes correlates strongly with transient and seasonal water table fluctuations this suggests a dominant influence of pore pressure effects on that part of the tilt signal the episodic nature of such effects makes it difficult to separate them from potential earthquake precursors during the build up of tectonic stress we present both an empirical and a deterministic approach to tackle this problem the former consists of removing pore pressure effects from the tilt signal by using simple empirical relations the latter is an attempt to model the physical process through finite element calculations based on biot s consolidation theory for elastic porous media although in our case some boundary conditions are poorly known it is believed that biot s theory is adequate to describe the observed phenomena

holocene palaeofire records in a high level proximal valley fill wilson bog mount lofty ranges south australia an elevated valley fill peat bog wilson bog near mount lofty south australia failed in november 2005 following a flooding event and exposed representative sections of the sediment infill two

vegetation change following mid holocene marine transgression of the torres strait shelf a record from the island of mua northern australia the pollen and sedimentary record from a coastal backdune swamp on the island of mua torres strait australia is presented a 4 55 m core collected from the swamp centre provides a record of vegetation and landscape change spanning the postglacial marine transgression to present prior to 6000 radiocarbon years before present yr bp results show mangrove vegetation encroaching on the core site periodically displacing non mangrove taxa until the establishment of an extensive mangrove forest between 6000 yr bp and 3000 yr bp within the mangrove community a transition from lower tidal rhizophora forest to an upper intertidal ceriops community is evident this is followed by the development of the current herbaceous freshwater swamp in the late holocene the dryland vegetation record is dominated by sclerophyll and rainforest elements with strongest forest representation occurring around the mid holocene before a decline in tree density and the establishment of open woodlands in the late holocene the data suggest vegetation change accompanied marine transgression and a humid mid holocene climate before stabilization of sea levels and the initiation of dominant on shore catchment processes signalling drier climatic conditions and possible human activity

mind the gap an absence of valley fill deposits identifying the holocene hypsithermal period of enhanced flow regime in southeastern australia the holocene sedimentary record in southeastern australia is present in a range of landscape settings such as upland swamps dells internally drained lake basins alluvial fans and mid catchmen

a re examination of the 1925 charlevoix quebec earthquake the 1 march 1925 charlevoix earthquake is one of the largest earthquakes known to have occurred in southeastern canada because it occurred in one of the most active seismic zones of southeastern canada and near now heavily populated regions understanding this earthquake may have implications for seismic hazard assessments of the region previous attempts have been made to study this earthquake using modern waveform analysis techniques but the source parameters could be only partially constrained due to a lack of good data recently a number of seismograms that had not been previously studied were rediscovered warranting a second look at the earthquake the best overall solution is strike 42 7 dip 53 7 rake 105 10 depth 10 km seismic moment 3 1 2 5 1025 dyne cm mw 6 2 ms 6 2 0 3 mb 6 5 0 4 source duration 5 sec and stress drop 35 bars the focal mechanism is consistent with many recent earthquakes in the charlevoix seismic zone but inconsistent with the regional stress field

interpreting charcoal in new zealand s palaeoenvironment what do those charcoal fragments really tell us the role of charcoal as a palaeoenvironmental indicator has never been fully or adequately explained charcoal fragments are often interpreted as evidence for natural fires caused by lightning strike during drought or dry climatic conditions generally no evidence is presented to show this to be the case the frequency of lightning strike in new zealand is not high and the extent to which it is a causal factor in generating forest fire is questioned the assumption is often made that charcoal fragments found in sedimentary deposits are local or at least reasonably local in origin this assumption is being challenged fine charcoal fragments appear to be transported regionally within new zealand it is highly likely that fine charcoal fragments are being transported from australia both by thermal convection during fires and during dust storm events to be deposited into new zealand sediments the consequences of this in interpreting new zealand s palaeo history requires researchers to at the very least provide charcoal counts within size parameters this is particularly so for archaeologists who would definitely need to show the presence of large charcoal fragments before interpreting the possibility of people in the landscape

a test of the longevity of impact induced faults as preferred sites for later tectonic activity the hypothesis that impact induced faults have been preferred sites for later deformation in response to lithospheric stresses has been suggested for several planets and satellites this hypothesis is investigated on earth by examining whether terrestrial impact structures show higher rates of nearby earthquake activity than do surrounding intraplate regions for 28 of 30 probable impact structures having an original crater 20 km or more in diameter the rates of nearby seismicity have been no higher than the regional background rates for two large probable impact structures vredefort and charlevoix with higher than normal rates of nearby seismicity factors other than slip on impact induced faults appear to control the occurrence of earthquakes it is concluded that impact induced faults at least on earth do not persist as lithospheric weak zones for periods in excess of several million years after the impact event

biomass burning in indonesia and papua new guinea natural and human induced fire events in the fossil record abstract microscopic charcoal preserved in sediments from ten wetlands in the indonesian and papua new guinea region provide a proxy record of regional fire events during the last 20 000 years two periods of high regional charcoal frequency are encountered during the last glacial transition 17 000 9000 years b p and the middle to late holocene 5000 years b p to the present despite the presence of humans in the region throughout the last 20 000 years there is no suggestion that on a regional spatial scale fire frequencies were solely related to changing subsistence patterns of the human population pollen data from these same sites suggest that during times of high charcoal the rate at which vegetation changes represented by the fossil pollen spectra also increases high climate variability may promote a greater community turnover rate and in turn a more fire susceptible forest community rapid climate change and high variability during the last glacial transition and intensification of el nino related climate variability during the middle to late holocene may have been important mechanisms for promoting fire in rainforest environments and maintaining diversity of tropical rain forests