Sclerochronological analysis of archaeological mollusc assemblages: methods,applications and future prospects

Accreting skeletal tissues found in bone, teeth, otoliths and molluscan shell act as sensitive recorders of local environmental and climatic conditions. Owing to their robust nature, ubiquity and abundance in the archaeological record as well as the potential for high-resolution data acquisition, the accreting skeletal tissues of archaeological molluscs are increasingly employed as palaeoenvironmental proxies. Researchers have chiefly utilised such proxies to extend instrumental records of environmental conditions through palaeoenvironmental reconstruction and explore the impact of environmental and climatic change on human populations. However, the use of environmental proxies from the archaeological record can be hampered by a number of methodological challenges including inadequate sampling strategies, appropriate calibration, the use of inappropriate proxies and the broad extrapolation of localised results. This paper reviews the use of molluscan shell from archaeological contexts as palaeoenvironmental proxies. We focus on the application of sclerochronology—a suite of high-resolution physical and geochemical data recovery methods widely used in conjunction with molluscan shell. This paper presents an overview of the potential of these techniques in approaching more nuanced understandings of human-environment interactions and how they can be more successfully incorporated into archaeological research.     

Overpressure in the Malay Basin and prediction methods

Predrill overpressure prediction is important for well planning and migration modeling for prospect evaluation. The Eaton (Journal of Petroleum Technology, 24 , 1972, 929) and Bowers (SPE Drilling & Completion, 10 , 1995, 89) methods are used worldwide for postdrill overpressure prediction using sonic log and predrill overpressure prediction using seismic interval velocity. In this research, these two methods were used for overpressure prediction using 3D anisotropic prestack depth‐migrated seismic interval velocity in a field of the Malay Basin. In the shallow overpressured zone, where the mechanism of overpressure is undercompaction, the onset of overpressure was predicted reasonably well using the Eaton and Bowers methods with their standard parameters (i.e., Eaton exponent 3 and Bowers loading curve) for seismic velocity. However, in the deep overpressured zone, where fluid expansion is the cause of overpressure generation, these methods underpredicted the high overpressure. In the deep overpressured zone, the overpressures were better predicted by applying a correction to the Eaton method. On the other hand, the Bowers unloading parameters for the fluid expansion mechanisms did not show any significant effect on overpressure prediction. Hence, in the study area, the Bowers method is not effective for 3D overpressure prediction using seismic velocity, whereas the Eaton method is more robust and can be used for 3D overpressure prediction from seismic velocity.     

Freezing and melting behaviors of H2O‐NaCl‐CaCl2 solutions in fused silica capillaries and glass‐sandwiched films: implications for fluid inclusion studies

Fluid inclusions of the H₂O‐NaCl‐CaCl₂ system are notorious for their metastable behavior during cooling and heating processes, which can render microthermometric measurement impossible or difficult and interpretation of the results ambiguous. This study addresses these problems through detailed microscopic examination of synthetic solutions during cooling and warming runs, development of methods to enhance nucleation of hydrates, and comparison of microthermometric results with different degrees of metastability with values predicted for stable conditions. Synthetic H₂O‐NaCl‐CaCl₂ solutions with different NaCl/(NaCl + CaCl₂) ratios were prepared and loaded in fused silica capillaries and glass‐sandwiched films for microthermometric studies; pure solutions were used with the capillaries to simulate fluid inclusions, whereas alumina powder was added in the solutions to facilitate ice and hydrate crystallization in the sandwiched samples. The phase changes observed and the microthermometric data obtained in this study have led to the following conclusions that have important implications for fluid inclusion studies: (i) most H₂O‐NaCl‐CaCl₂ inclusions that appear to be completely frozen in the first cooling run to ?185°C actually contain large amounts of residual solution, as also reported in some previous studies; (ii) inability of H₂O‐NaCl‐CaCl₂ inclusions to freeze completely may be related to their composition (low NaCl/(NaCl + CaCl₂) ratios) and lack of solid particles; (iii) crystallization of hydrates, which is important for cryogenic Raman spectroscopic studies of fluid inclusion composition, can be greatly enhanced by finding an optimum combination of cooling and warming rates and temperatures; and (iv) even if an inclusion is not completely frozen, the melting temperatures of hydrohalite and ice are still valid for estimating the fluid composition.     

Louis D. Brandeis: Advocate Before and On the Bench

On January 3, 1916, members of the Chicago Bar Association listened attentively as one of the country's best-known attorneys and reformers rose to speak to them. No one in the audience, not even their guest of honor, knew that within a few days the President of the United States would nominate him to become a member of the United States Supreme Court. In his speech that day, Louis Dembitz Brandeis spelled out his views on the problems confronting law in a rapidly changing society, and placed much of the blame for social unrest and popular disrespect for the law on judges who refused to recognize the economic and social developments taking place all around them:     

GEOARCHAEOLOGICAL EVIDENCE FROM DESERT LOESS IN THE NAZCA–PALPA REGION,SOUTHERN PERU: PALAEOENVIRONMENTAL CHANGES AND THEIR IMPACT ON PRE‐COLUMBIAN CULTURES*

The paper presents proxies from an interdisciplinary geoarchaeological working group. Sediment analyses and geomorphological studies, radiocarbon ages of snail shells and luminescence dating of loess allow a preliminary chronology of the environmental evolution of the eastern Atacama desert, Nazca–Palpa region (southern Peru). Until now, typical desert loess was unknown from the arid western flank of the Andes (southern Peru). The loess points to periods of more humid conditions with open grasslands at the eastern Atacama desert margin in the early and middle Holocene. In the footzone of the Andes, aridification set in before the Paracas Culture (c. 800–200 bc ) evolved, but the Cordillera Occidental remained semi‐arid. A second push of increasing aridity started at the latest in the Middle Nazca Period (after ad 250). During this time, the Nazca settlement centres moved upstream through the river oasis, following the eastward‐shifting desert margin. It is possible that culminating aridity after ad 600 caused the collapse of the Nazca civilization. During the Late Intermediate Period (ad 1000–1400), more humid conditions favoured the massive reoccupation of the eastern Atacama up to a distance of about 40 km from the Pacific coast. Since the 14th and 15th centuries, the Palpa region has again been part of the hyper‐arid Atacama. The study shows that in the Nazca–Ica region, the deep cultural changes of Pre‐Columbian civilizations were not caused by catastrophic run‐off of El Niño events, but by a shifting eastern desert margin due to the changing monsoonal influence.