Artifacts, dating

This EPMA line scan was analysed by wavelength dispersive spectroscopy, being part of a study by Horz and Kallfass of ornamental and ceremonial artifacts dated to approximately AD 50-300, recovered from the Royal Tombs of Sipan, Peru. 

The Ixtepeque obsidian source is located 85 km from the El Chayal source zone (ca. 300 km from Trinidad de Nosotros, as the crow flies). It is found at archaeological sites east and north of the source, along the coast of Belize, northeastern Pet6n, the Belize Valley, and northern Yucatan (7, 14). Obsidian artifacts dating to the Late Preclassic, Terminal Classic and Postclassic periods are predominately from this source and it was the main source during the Postclassic period (77, 75, 17). 

Below Unit B a silty sand layer (Unit C) was encountered in the cores taken between the mouth of the Great Wadi and the center of the Kom el Ahmr. Unit C contained a sequence of Old Kingdom to late Predynastic artifacts dating from about 2500 B.C. to 3200 B.C. Below Unit C, a very compact, well-sorted thick layer of Nile clay and sand was encountered (Unit N). No cores or trenches reached below this sedimentary deposit. Unit N contained occasional Predynastic ceramic and flint artifacts. Samples were collected from each 10-15-cm auger cut within each sedimentary unit in each core or trench. In addition, numerous samples of the Neonile deposits and other sediments from the nearby low desert and Great Wadi were taken for analysis. 

Incipient, Initial, Early, Middle, Late, and Final.) Two Early Jomon occupations are represented one between 4450 and 4000 b.c. and another between 3690 and 3190 b.c. The majority of features and artifacts date from these periods. The site was probably not continuously inhabited but was reoccupied at regular intervals. A limited Late Jomon component should date to around 1500-1000 b.c. 

Metallic tin is derived mainly from the mineral cassiterite (Sn02) and to a lesser extent from the sulfide ore stannite CuiS-FeS-SnSi, although it can be derived from rarer minerals such as malayaite, CaSnSiOs. Tin is one of the earliest metals known and has influenced our lifestyle through the ages. Tin alloy artifacts dating from about 5000 years ago have been unearthed at Ur, the site of ancient Babylonia. Today, we are exposed to tin on a daily basis through the use of tinplated food cans of alloys such as pewter, bronze, brass. 

Crystalline phosphate layers of natural origin are rare. Vivianite (Fe2 (P04)2-4H20) layers have been observed on steel artifacts dating from around the third century AD, and not withstanding speculation that the Romans had... 

Accurate, precise isotope ratio measurements are used in a variety of applications including dating of artifacts or rocks, studies on drug metabolism, and investigations of environmental issues. Special mass spectrometers are needed for such accuracy and precision. 

Rubidium-87 emits beta-particles and decomposes to strontium. The age of some rocks and minerals can be measured by the determination of the ratio of the mbidium isotope to the strontium isotope (see Radioisotopes). The technique has also been studied in dating human artifacts. Rubidium has also been used in photoelectric cells. Rubidium compounds act as catalysts in some organic reactions, although the use is mainly restricted to that of a cocatalyst. 

The constant half-life of a nuclide is used to determine the ages of archaeological artifacts. In isotopic dating, we measure the activity of the radioactive isotopes that they contain. Isotopes used for dating objects include uranium-238, potassium-40, and tritium. However, the most important example is radiocarbon dating, which uses the decay of carbon-14, for which the half-life is 5730 a. 

Exponential decay is quite regular starting with a given amount of a substance at t = 0, this amount will fall to V2 its original value after one half-life, to 1/4 after two half-lives, Vs after three half-lives, and so forth. This regularity has its usefulness, and the decay of has been widely employed to date archeological artifacts [3]. 

The Zag meteorite fell in the western Sahara of Morocco in August 1998. This meteorite was unusual in that it contained small crystals of halite (table salt), which experts believe formed by the evaporation of brine (salt water). It is one of the few indications that liquid water, which is essential for the development of life, may have existed in the early solar system. The halite crystals in the meteorite had a remarkably high abundance of 128Xe, a decay product of a short-lived iodine isotope that has long been absent from the solar system. Scientists believe that the iodine existed when the halite crystals formed. The xenon formed when this iodine decayed. For this reason, the Zag meteorite is believed to be one of the oldest artifacts in the solar system. In this lab, you will use potassium-argon radiochemical dating to estimate the age of the Zag meteorite and the solar system. 

Skinner, A. F. and M. N. Rudolph (1996), Dating flint artifacts with electron spin resonance, in Orna, M. V. (ed.), Archaeological Chemistry, Vol. 5, Organic, Inorganic and Biochemical Analysis, Advances in Chemistry Series, ACS, Washington, DC, pp. 37-46. 

Fig. 1. Co-addition of four UVES pipeline spectra of NGC 6397/TO201432 (observing dates 2000-06-18 and 22, two spectra per night). The resulting spectrum was arbitrarily normalized at 6410 and 6690 A. As blaze residuals are not properly accounted for in the pipeline order merging, the echelle order pattern is clearly visible in the merged spectrum. With an amplitude of 2 %, these instrumental artifacts do not allow to derive Baimer-profile temperatures to better than 200-300K.

One of the limitations of radiocarbon dating artifacts is due to the half-life of the carbon-14, 5730 years. In radiochemistry, a good rule of thumb is the following when an element decays for more than about 10 times its half-life, there is very little left to measure accurately. In the case of C-14, that time is 10 x 5730 yr or 57300 years. 

Figure 5. Schematic cross section of the cave of Lachaise-de-Vouthon, Charente, France, showing the relation between dated travertine layers and the artifact- and...

---