H.M. Rendell

Early Tool-Making in Asia : Two-Million-Year-Old-Artefacts in Pakistan

For the last half-century, the story of very early hominids, and their stone industries, has been almost exclusively ‘in Africa’. This first report of a very early industry takes the story ‘out of Africa’ and into the Indian sub-continent – that is, in a geographical direction towards the early industries of eastern Asia.

The impact of the farming practice of remodelling hillslope topography on badland morphology and soil erosion processes

Abstract Badland landforms, created in Plio–Pleistocene clay landscapes of the Basilicata region of southern Italy, form marginal features in a semi-arid landscape dominated by the widespread cultivation of subsidised cereals. These badland features are high relative relief forms exhibiting a high drainage density and steep slopes, with slope angles typically in excess of 35°. Economic incentives to increase agricultural productivity have resulted in the practice of remodelling these marginal areas using heavy earth-moving equipment. Remodelling the badland features creates longer slopes at lower angles, which can be cultivated using conventional farm machinery. These changes in hillslope morphology have altered the degree to which soil erosion processes operating in these areas are spatially coupled. In the badland areas, erosion and deposition are strongly localised with minimal sediment delivery to ephemeral or perennial channel systems. The economically-driven change in land use from visually striking badland areas to newly remodelled fields for agricultural use results in an increase in the coupling of drainage networks and a net increase in soil erosion.

Thermoluminescence spectra of igneous quartz and hydrothermal vein quartz

Variations in thermoluminescence spectra are reported for four types of geological quartz examined with a new spectrometer featuring dual imaging photon detectors that separately and simultaneously detect (1) uv-blue (200–450 nm) and (2) blue to near infrared (400–800 nm) emission. Samples show striking differences which appear to be characteristic of their geological origin. Volcanic quartz phenocrysts from acid volcanics show red thermoluminescence (TL) emission bands centered at 620–630 nm that are 100 times more intense than similar bands in other quartz, while a violet emission at 420–435 nm was observed exclusively in igneous quartz (volcanic and granitic). A broad emission band centered at 560–580 nm was observed only in quartz formed hydrothermally. Massive quartz from Li-rich pegmatite bodies shows narrow, intense 470 nm emission bands at 230° C apparently related to Al and to Ge defects detected with electron paramagnetic resonance (EPR), and emission bands at 330 and 280 nm, possibly related to recombination at oxygen vacancies. The common 380 nm emission band of quartz was observed in both volcanic and granitic quartz, but was not detected in either the pegmatitic or the hydrothermal vein quartz. Observed spectral variation is identified as a potential source of error in luminescence dating.

Crystal field effects on the thermoluminescence of manganese in carbonate lattices

Abstract Thermoluminescence emission spectra are reported for a wide range of carbonates. All the samples show Mn luminescence centres and the spectra variously include narrow and features, when the Mn is in low concentration, or broad emission bands at high concentrations. The form of the spectra change with temperature, and for some Mn concentrations, alter from broad to narrow band spectra with increasing temperature. In calcite there is concentration quenching of the luminescence when the Mn impurity levels exceed ∼ 1000 ppm which varies with glow peak temperature. The emission wavelengths of the Mn show monotonic dependencies, in both rhombohedral and orthorhombic lattices, as a function of the length of the metal to oxygen bonds in the various minerals, and the presence of Mn in alternative sites is revealed for dolomite. The detailed line spectra can be related to the Mn ion energy level diagram, as perturbed by the crystal field term, which for emission in rhombohedral calcite has a value of ∼ 1000 cm −1 , but for orthorhombic sites in aragonite is ∼ 1200 cm −1 .

Thermal treatments and emission spectra of TL from quartz

Abstract The intrinsic defect structure of quartz is sensitive to heat treatments, and this is reflected in changes in TL sensitivity and also the relative intensity of the component glow peaks. It is also known that even for the same crystal, there can be changes in the luminescence spectra. This paper reports on spectral changes induced in the TL of quartz as a result of a variety of thermal treatments. Emission spectra obtained from synthetic, hydrothermal and volcanic quartz samples were compared. Heat treatments to 1000°C enhanced the TL signals by factors of up to 1000 times. The rate of cooling changed the relative intensities of the component emission bands in all samples. In the volcanic quartz material, the ratio of red to blue emission is particularly sensitive to the cooling rate. The influence of the spectral features on conventional polychromatic TL data is discussed.

Quality assurance in luminescence dating

Recent advances in luminescence dating have led to increasing application of the technique to sediments from a wide range of depositional environments, many of which are characterised by rapid transport and deposition under turbid conditions. The complete zeroing of the luminescence signal, by exposure to light, is critical to obtaining an accurate age for deposition of the sediment, before any geomorphological or palaeoenvironmental reconstructions can be undertaken based on this chronology. Comparison of luminescence dates with independent age control is rare, due to a lack of suitable material in natural contexts and thus the accuracy of the luminescence dating technique has yet to be proven in many depositional environments. There is therefore a clear need for both quality assurance in luminescence dating and a method for assessing the accuracy of each date. This paper describes and demonstrates a quality assurance method that can be used as part of a routine dating programme and which can discriminate against samples which would give inaccurate dates.

Thermoluminescence dating of a 10 m loess profile in Pakistan

Abstract Thermoluminescence (TL) dates are reported for a 10 m section of loess in northern Pakistan. Age determinations were contrasted using the Additive Dose (N + beta − I 0 ) and signal regeneration methods. TL dates increase monotonically with depth down the profile with the (N + beta − I 0 ) approach up to a value of 135 ka for the deepest sample. Ages assessed by regeneration after optical bleaching tend towards a limiting age of 72 ka. The failure of the regenerative approach appears to result from a sensitivity change on bleaching which is proportional to the natural TL signal. This effect is modelled in terms of changes in TL efficiency.

Luminescence dating of sand ramps in the Eastern Mojave Desert

Abstract Until recently the timing of the movement of sand and accumulation of sand by aeolian processes in the Eastern Mojave Desert has remained the subject of speculation. The results of a luminescence dating program involving 78 samples of material from nine sand ramp complexes have enabled recognition of regional and local patterns of sand accumulation in the Eastern Mojave. The study area extends from Lake Manix, in the west, to the Colorado River, in the east. The periods of accumulation have been identified on the basis of quartz TL dating, and potassium feldspar TL and IRSL dating. At a regional scale, two major depositional phases can be identified: (1) Late Pleistocene: 20–30 ka, with sequences at Hanks Mountain, Balch, Dale Lake and the Big Marias; and (2) Late Pleistocene-Early Holocene: 15-7 ka with sequences at Cat Dune, Dale Lake, Iron Mountain, Big Marias (above palaeosol) and, at the western end of the study area, at Soldier Mountain (20-7 ka). Late Holocene sequences appear to be much more localized, and are confined to the West Cronese, Old Dad Mountain and Balch sand ramps. The earliest phases of sand accumulation on the ramps studied immediately predate the formation of pluvial Lake Mojave (ca. 24.5 ka). The later main phases of accumulation coincide with the existence of Lake Mojave and the end of accumulation on the majority of the sand ramps immediately post-dates the final end of Intermittent Lake Mojave III (9.7 ka). The continuity of sand supply to potential deflation areas is seen as a critical condition for accumulation of material on the sand ramps during the Late Quaternary in the Eastern Mojave.

Underwater bleaching of signals from sediment grains: new experimental data

Abstract The results of an underwater bleaching experiment are reported. The purpose of the experiment was to evaluate the degree to which thermoluminescence (TL) and optically stimulated luminescence (OSL) signals are reduced by a three hour exposure to light at different water depths. Samples of quartz and feldspar separates were annealed in the laboratory and then given fixed doses of laboratory beta radiation before exposure. The results indicate that a three hour light exposure is sufficient to zero the optical signals down to water depths of 10 m for feldspar infra-red stimulated luminescence and 12–14 m for quartz OSL. The TL results for the same quartz and feldspar samples exhibit some bleaching effects, with TL signals at 14 m water depth being reduced to 50–65% of the initial value. Scatter of the TL results limits their interpretation.

Late Pliocene Artefacts from Northern Pakistan

In an earlier article (Rendell and Dennell I985), we reported the I983 discovery of handaxes and other stone artefacts in firmly dated contexts between o.s and 0.7 million years old at two localities in northern Pakistan. We now report the discovery of what we regard as hominid-struck stone artefacts and/or debitage in a geological horizon at another locality in northern Pakistan that is, in our opinion, ca. 2 million years old. These artefacts were also discovered in I983, in the area near Riwat, south-east of Rawalpindi (fig. i), where members of the British Archaeological Mission to Pakistan had previously been mapping a complex series of Upper Pleistocene fluviatile and aeolian deposits spanning the last I50,000 years. The first to be found was embedded in a gritstone outcrop at the base of a deeply incised gully. Flow in the gully is ephemeral, and this outcrop now forms the head of a small waterfall after heavy rains. Erosion of this gritstone had exposed a quartzite cobble (fig. 2) from which some flakes had been detached. As the flaked surfaces were still partially embedded in the gritstone, the flaking of this piece could not have taken place after the erosion of the gritstone to its present form. The piece was therefore photographed and carefully chiselled out and was found to have been flaked in three planes, involving the removal of six and perhaps seven flakes (fig. 3). Downstream of this find, the same conglomerate horizon is exposed as a series of large tabular fragments (up to io m2) caused by undercutting and subsequent fracturing. Careful inspection of the surfaces of these blocks for other quartzite clasts