W. Jack Rink

The tsunami of 13 December A.D. 115 and the destruction of Herod the Great's harbor at Caesarea Maritima, Israel

Underwater geoarchaeological excavations on the shallow shelf (∼10 m depth) at Caesarea, Israel, have documented a tsunami that struck and damaged the ancient harbor at Caesarea. Talmudic sources record a tsunami that struck on 13 December A.D. 115, impacting Caesarea and Yavne. The tsunami was probably triggered by an earthquake that destroyed Antioch, and was generated somewhere on the Cyprian Arc fault system. The tsunami deposit consisted of an ∼0.5-m-thick bed of reverse-graded shells, coarse sand, pebbles, and pottery deposited over a large area outside of the harbor. The lower portion of the deposit was composed of angular shell fragments, and the upper portion of whole convex-up Glycymeris spp. shells. The sequence records tsunami downcutting (∼1 m) into shelf sands, with the return flow sorting and depositing angular shell fragments followed by oriented whole shells. Radiocarbon dating of articulated Glycymeris shells, and optically stimulated luminescence (OSL) dates, constrain the age of the deposit to between the first century B.C. and the second century A.D., and point to the tsunami of A.D. 115 as the most likely candidate for the event, and the probable cause of the harbor destruction.

The 1992–1993 Excavations at the Die Kelders Middle and Later Stone Age Cave Site, South Africa

AbstractRenewed excavations at Die Kelders Cave 1, South Africa, have confirmed and augmented prior findings. The new excavations focused on the Middle Stone Age (MSA) deposits, but they added seeds, pips, and crayfish to the categories of Later Stone Age (LSA) food debris and artifacts recovered earlier. With respect to the MSA deposits, the principal new findings are: 1) previously unrecognized site formation processes ,including phosphatization by guano, microfaults, and slippage faces, and numerous minor interruptions in sand accumulation that correspond to Short occupation episodes; 2) ESR dates that place the top of the MSA sequence between 80,000 and 60,000 years b.p.; 3) fine-grained rock types, flake-blade sizes and other features that suggest the top of the sequence contains either the Howiesons Poort or a similar silcrete-rich variant of the MSA; 4) a pattern of artifact and bone abundance in newly recognized microstrati-graphic units that suggests that eagle owls (rather than people) accumula...

Monte Carlo determinations of the beta dose rate to tooth enamel

The results of Monte Carlo simulations of the beta dose rate to enamel are presented. The dose rates are the most comprehensive to date, incorporating the beta spectrum from 21 different radionuclides, all internal conversion and Auger electrons, the majority of the bremsstrahlung radiation, effects due to radon loss in the uranium series, and variations in the moisture content of the sediment. Applications to a new dating technique in archaeology using electron spin resonance and beta-gradient isochrons are discussed.

New Quartz Optical Stimulated Luminescence Ages for Beach Ridges on the St. Vincent Island Holocene Strandplain, Florida, United States

Abstract St. Vincent Island, located on the northwest Gulf of Mexico coast of Florida, U.S.A., preserves a well-developed beach ridge plain that is generally believed to have begun to form during the mid-Holocene period. This study evaluates the potential of optical stimulated luminescence (OSL) to appraise the proposed evolution and progradation of this strand-plain. Optical stimulated luminescence was used to obtain the ages of the quartz samples extracted from seven vibracores at two depth intervals. The single-aliquot regenerative-dose (SAR) OSL ages increase from the shores on the Gulf of Mexico to St. Vincent Sound. The younger ridge set yielded ages of 370 ± 49 to 1890 ± 292 years (AD 2004 datum) conferring an interridge accretion time range of 78 to 148 years assuming uniform sediment accumulation. The oldest ridge set yielded ages of 2733 ± 404 to 2859 ± 340 years, consistent with the estimated age based on archaeological materials of 3000–4000 years ago. For the southwestern beach ridge set, the ages provide insights on the aeolian accumulation and reworking processes effective throughout the ridges despite their vegetation cover. Our results highlight the potential of OSL as an application to use not only for dating but also for coastal dynamics assessments. The SAR–OSL ages presented herein provide new reliable absolute ages on the beach ridge sequence of St. Vincent Island and improve the age control on formation of barrier island sequences in the Florida panhandle region.

Dose response of ESR signals in tooth enamel

Radiation-induced growth in the g = 2.0018 signal in fossil tooth enamel can be used to determine the age of fossil teeth. Porat and Schwarcz (1994) [Integrative Paths to the Past: Paleoanthropological Advances in Honor of F.C. Howell (eds Corrucini R. and Ciochon R.), pp. 521–530. Prentice- Hall, Englewood Cliffs] suggested that the radiation sensitivity of all tooth enamel is quite similar, and have constructed a Universal Growth Curve (UGC) to estimate equivalent dose (DE). To further test this concept, we use a saturating exponential of the form I = Imax (1 - exp[- D/D0]) to fit normalized ESR intensity (I) data for teeth from various sites. We show that the ranges of fitting parameters Imax and D0 overlap for modern and fossil enamels. This suggests that no significant diagenetic changes in the enamel have occured to affect the ESR signal in most samples. Sensitivity, as measured by normalized intensity at D = 32 Gy, varies by 22% (n = 24); modern samples have the same mean sensitivity, but show less variation (8%). The normalized dose-response curve (natural intensity vs DE) is a good predictor of DE, although there are some outliers. Imax is strongly correlated with D0, suggesting a relationship between trap concentration and capture cross-section for migrating charges.

Comparison of ESR signal dose-responses in modern and fossil tooth enamels

Abstract The dose response of ESR signals in enamels extracted from young archaeological (modern) teeth aged less than 200 y were compared with fossil teeth ranging in age from about 50 to 110 ka. We aimed to test the accuracy of equivalent dose (ED) determinations on modern teeth with a known (near zero) ED because zeroing the signal in tooth enamel is not possible. The modern teeth showed departure from true single saturating exponential dose response, but generally gave very good agreement with the expected near zero ED (±5–10% in the worst cases). Linear fitting was better than SSE fitting within the lower dose ranges. However, the fossil teeth showed significant variability and departure from the well-behaved dosing characteristics of modern enamels. When the natural signal was excluded, ED s were found to be strongly dependent upon the choice of the first added dose in both cases studied using a modulation amplitude of 0.32 mT, and strongly dependent upon choice of modulation amplitude in another case. These latter observations, when considered in relation to modern enamel behaviour, raise questions about the possibility of diagenetic change in the fossil enamel.

Billion-year age dependence of luminescence in granitic quartz

Abstract Quartz grains from granites of known age ranging from 25 to 1040 million years old (Ma) that were previously studied using electron spin resonance (ESR), have been further studied using thermoluminescence (TL) and optically stimulated (green light) luminescence (OSL). Both inadvertently light-exposed quartz grians (Q1 samples) and the same quartz grains after further controlled light exposure (Q2 samples) plus gamma dose yielded signal characteristics strongly correlated with the crystallization age of the host granite. TL peak temperature in Q1 samples was positively correlated with age, whereas an anticorrelation with age was found for the OSL response after beta dose and standard preheating to Q1 samples. Regenerated TL sensitivity was found to decline in linear fashion with age ( R 2 =0.998) for Q2 samples. The various correlations with age appear better than those found previously in these samples using ESR signals. It is concluded that luminescence pathways are altered over geologic time in a similar way for all the granites, and these changes may be potentially useful as a long-ranging quartz geochronometer.

Natural Residual Thermoluminescence as a Method of Analysis of Sand Transport along the Coast of the St. Joseph Peninsula, Florida

Abstract St. Joseph Peninsula is located in Florida, along the northeast coast of the Gulf of Mexico. Natural residual thermoluminescence (NRTL) analysis of quartz grains extracted from sands at eight localities showed a gradual reduction in NRTL intensity from south to north, which is also the accepted direction of longshore transport. Differences in NRTL reduction were also noted between grain size fractions, indicating either differential response to light exposure during travel, or different amounts of exposure between grain sizes. Laboratory experiments using simulated sunlight exposure in air and seawater were combined with natural exposure experiments, wherein differences in residence time in the swash zone between grain size fractions were quantified. In this study, sediment residence times in the swash zone along the St. Joseph Peninsula were estimated to vary from ∼25 days to ∼9 days depending on grain size. A 67% variance in littoral zone residence between 90–150-µm and 150–212-µm grains is revealed. The results of this study indicate the significance of NRTL as a novel method of sand transport analysis.

Optically stimulated luminescence dosimetry with gypsum wallboard (drywall)

Gypsum wallboard (drywall) represents an attractive target for retrospective dosimetry by optically stimulated luminescence (OSL) in the event of a radiological accident or malicious use of nuclear material. In this study, wallboard is shown to display a radiation-induced luminescence signal (RIS) as well as a natural background signal (NS), which is comparable in intensity to the RIS. Excitation and emission spectra show that maximum luminescence intensity is obtained for stimulation with blue light-emitting diodes (470 nm) and for detection in the ultraviolet region (290-370 nm). It is necessary to decrease the optical stimulation power dramatically in order to adequately separate the RIS from the interfering background signal. The necessary protocols are developed for accurately measuring the absorbed dose as low as 500 mGy and demonstrate that the RIS decays logarithmically with storage time, with complete erasure expected within 1-4 d.

Beyond 14C Dating

In the 1980s and 1990s a range of new dating methodologies has emerged that are based on radiation exposure effects in host materials. These methodologies include electron spin resonance (ESR) and various forms of luminescence dating (OSL, IRSL, and TL). These techniques require careful sampling strategies that are best accomplished by archaeologists and geochronologists working together. This chapter aims to provide archaeologists and geochronologists with an introduction to the sampling approaches and range of problems that can be solved in archaeology, with an accompanying description of the physical basis of the methods. These radiation exposure techniques, along with fission-track methods, are compared with recently improved conventional radiogenic isotopic dating approaches such as mass spectrometric uranium series and 40Ar/39Ar dating. Emphasis is placed on considerations of how to identify datable materials and selection of the appropriate technique for dating in a site, with due consideration to various problems and advantages in the various approaches.