Obsidian hydration dating: accuracy and resolution limitations imposed by intrinsic water variability

Obsidian hydration dating typically yields a range of ages for a single chronometric measurement, even after controlling for source chemistry and effective hydration temperature. Previously published data suggest that this range is due to hydration rate variations caused by variability in the concentration of intrinsic water, and specifically hydroxyl ions, in the obsidian. Such variability exists within any given obsidian source, and even within any particular specimen. This paper analyzes the effect on age estimates of intrinsic water variability and concludes that if a controlled sample of obsidian yields a range of ages, there is no way to tell whether the range is due to long site use or to variations in hydroxyl concentration. At present there is no robust and cost-effective protocol for measuring hydroxyl concentration. Suggested guidelines for obsidian hydration dating are developed using a case study. These findings do not invalidate obsidian hydration as a chronometric technique, but they do suggest limits to the temporal resolution achievable.     

Die Petrografie himyarischer Keramik vom Jabal al ‘Awd,Jemen

Early Himyarite ceramics (first century BC–third century AD) from the Jabal al ‘Awd in Yemen are classified by visual criteria into a number of ware groups. Following classification the ceramics were investigated with petrologic methods (porosity and density). Mineralogical and physical properties were determined from thin sections according to cathodo‐luminescence spectra. The ceramics are divided into six ware groups, each of which has distinctive material properties and mineralogy.     

A New Type of Composite Anchor Dated to the Fatimid-Crusader Period from the Dead Sea, Israel

Two composite anchors of a kind not hitherto identified, each composed of a re-used ashlar block, a wooden shank, two arms and a rope, were discovered recently on the Dead Sea shoreline. Two additional anchor weights of identical type were found in the same region. The two well-preserved anchors were dated to the Fatimid-Crusader period. The shank and the arms were made from local tree species: Christ thorn and tamarisk, and both ropes of date-palm.
© 2008 The Authors     

关于《倦勤斋陈设档》的几点认识

本文分析了故宫博物院所藏《倦勤斋陈设档》的状况,并据《陈设档》所载内容.结合历史事件及历史文献的记载,参阅《中国古籍善本总目》等著录情况.对陈494《陈设档》的立档年限进行了考证。     

Lake Nuga Nuga: a Levee‐dammed Lake in Central Queensland,Australia

Lake Nuga Nuga is a levee‐dammed lake in the dry sub‐humid tropics of the Fitzroy Basin in Central Queensland, Australia, that has expanded significantly since it was first mapped in 1866. ²¹⁰Pb dating of a sediment core from the lake indicates that the rate of sedimentation has been constant for the past 67 years at 3 mm yr^?1 despite widespread clearing and land use intensification in the catchment during that time. Pollen analysis confirms this and shows that there was little change in vegetation during the early settlement period (1863–1962), but the intensification of land use that started in the early 1960s brought about a dramatic change in the vegetation communities. This study demonstrates that while sediment production may be significantly impacted by land‐use activities, sediment delivery is primarily controlled by topography.     

Uranium-series dating rock art in East Timor

At many sites throughout the world rock art paintings have been covered by naturally deposited calcite laminations, which we demonstrate can be individually dated by recently improved uranium-series methods. Here we report the application of multi-collector inductively coupled plasma mass spectrometry to measure the ages for carbonate coatings that bracket red pigment at Lene Hara cave, East Timor, which could be evidence of human painting. These analyses establish the feasibility of dating milligram samples of finely layered calcite deposits associated with archaeological evidence of human occupation. In addition to confirming an age of less then 6300 years for the visible red paintings on the carbonate surface we also report a substantially older age of 24,000 to 29,300 years for a similar, older red pigment lamination providing possible evidence for an earlier painting episode.     

Neolithic occupation and mid-Holocene soil formation at Encosta de Sant'Ana (Lisbon,Portugal): a geoarchaeological approach

Excavations at the archaeological site of Encosta de Sant'Ana (Lisbon, Portugal) uncovered a mid-Holocene buried alluvial soil associated with early Neolithic occupation layers. Routine laboratory analyses and micromorphological observations were undertaken on the soil material. Humic acids from its Ab horizon, as well as Neolithic ecofacts, were radiocarbon dated. The dates obtained indicate that soil was formed between c. 8.0 and 6.0 cal ka BP and that the pedological evidence fits the record of the North Atlantic Holocene IRD events (“Bond events”) and the so-called “Holocene climate optimum”. The geoarchaeological record reveals that Neolithic inhabitants settled upon a stable surface, still affected by soil formation that was suddenly interrupted by slope wasting, probably in correspondence to Bond event 4, at c. 6.0 cal ka BP.     

A simple Bayesian approach to tree‐ring dating

Tree‐ring dating involves matching sequences of ring widths from undated timbers to dated sequences known as ‘master’ chronologies. Conventionally, the undated timbers (from a building or woodland) are sequentially matched against one another, using t‐tests to identify the relative offsets with the ‘best’ match, thus producing a ’site’ chronology. A date estimate is obtained when this is matched to a local master chronology of known calendar age. Many tree‐ring sequences in the UK produce rather low t‐values and are thus declared not to have a ‘best’ match to a master chronology. Motivated by this and the routine use of Bayesian statistical methods to provide a probabilistic approach to radiocarbon dating, this paper investigates the practicality of Bayesian dendrochronology. We explore a previously published model for the relationship between ring widths and the underlying climatic signal, implementing it within the Bayesian framework via a simulation‐based approach. Probabilities for a match at each offset are produced, removing the need to identify a single ‘best’ match. The Bayesian model proves successful at matching in both simulated and real examples.     

Rodent-based age appraisal of the Lower Siwalik Subgroup of Kalaunta,Ramnagar, Jammu,India

Parmar, V., Magotra, R., Norboo, R. & Prasad, G.V.R., July 2016. Rodent-based age appraisal of the Lower Siwalik Subgroup of Kalaunta, Ramnagar, Jammu, India. Alcheringa 41, xx-xx. ISSN 0311-5518.

Rocks of the Lower Siwalik Subgroup exposed around Ramnagar town in Jammu, India, have been known for more than 90 years to yield Chinji-equivalent (14.2–11.2 Ma) hominoid fossils. In 1997, the fossil ape Sivapithecus reported near Kalaunta village in the vicinity of Ramnagar was argued to be about 18 Ma old by its discoverers. This had implications for hominoid evolutionary studies, as molecular clock calibrations are commonly based on Sivapithecus first appearance datum (FAD). In a paper published in 2010, the identification of this hominoid tooth was questioned and reassigned to a suid. Recently, based upon the discovery of an indeterminate fossil bovid from the supposedly hominoid-yielding site near Kalaunta, an age estimate between ca 13.9 and 10.8 Ma was provided. As rodent biochronology has proven to be useful in age assignment of upper Cenozoic terrestrial sequences, the age of the fossil-bearing Lower Siwalik Subgroup of Kalaunta is re-assessed based upon newly recovered cricetid taxa. The cricetid rodents from this site comprise Punjabemys downsi and P. mikros. These two species are known to exist in the well-dated Potwar Siwalik Group succession between 14.3 and 12.6 Ma and between 16.3 and 13.0 Ma, respectively. Based on the overlapping temporal ranges of the cricetid taxa and an indeterminate Bovidae (ca 13.9–10.8 Ma) reported previously from this area, an age of 13.9–13.0 Ma is inferred for rocks occurring in the vicinity of Kalaunta. The new finds refute earlier claims of rocks in the area extending back to ca 18 Ma or as young as 10.8 Ma.

Varun Parmar [varunparmarvp@gmail.com], Rahul Magotra [rahulmagotra01@gmail.com] and Rigzin Norboo [norboo04@gmail.com], Post Graduate Department of Geology, University of Jammu, Jammu, 180 006, India; Guntupalli Veera Raghavendra Prasad [guntupalli.vrprasad@gmail.com], Department of Geology, Centre for Advanced Studies, University of Delhi, Delhi, 110 007, India.