Fossil Canis from the tar pits of La Brea,Peru

New fossil material has been obtained from La Brea, Peru. Included in this material are remains of a large wolflike canid which could not be referred to any living or fossil South American canine genus. Comparison with fossil canids from Rancho La Brea, Calif., shows that it closely resembles Canis (Aenocyon) dirus Leidy.     

Radiocarbon dating of coastal peat, barrow, alaska

A buried, frozen section of peat from sea level yielded radiocarbon dates between 700 and 2600 B.C.; it suggests burial by a transgressing sea.     

Radiocarbon dating with electrostatic accelerators: dating of milligram samples

The recently developed direct counting technique for radiocarbon atoms has been used to measure the relative numbers of such atoms in various geological samples which had earlier been dated by the beta-ray counting method. Sample weights ranged from 3.5 to 15 milligrams. The dates determined by the two methods are consistent with each other. Further experience with the new method is also reported.     

Radiocarbon: analysis of inorganic carbon of fossil bone and enamel

Carbon dioxide from calcium carbonate in fossil bone can be selectively separated from carbon dioxide in bone apatite by hydrolyzing the sample first in acetic acid and then in hydrochloric acid. Radiocarbon analyses of the inorganic carbon dioxide in three samples of known age clearly show calcium carbonate in fossil bone to be secondary and the carbonate of bone apatite to be indigenous and suitable for dating in some cases. Agreement between dates on collagen-bone apatite pairs increases the level of confidence.     

A Climatic Record from Searles Lake,California

Data concerning past climatic conditions in arid California have been presented. Palynological and geological evidence points to the existence of past cooler moister climates and to climatic fluctuations. These have been tentatively correlated with late Pleistocene events in glaciated North America. The existence of a rather extensive woodland community at times of more favorable moisture conditions seems to be indicated.     

Precambrian Mollusc-like Fossils from Inyo County, California

Probable molluscan fossils have been discovered in the Reed Dolomite, White-Inyo Mountain area, Inyo County, California. They consist of small orthoconic shells with relatively large bilaterally symmetrical protoconch-like initial termini. Some individuals have a 'U-shaped" (in transverse section) internal structure. The fossils occur at least 900 meters below the strata containing the earliest known olenellid trilobites and are therefore considered Precambrian.     

Clay Mineral Composition of Borate Deposits and Associated Strata at Boron,California

X-ray analyses of samples from lacustrine deposits in the Kramer borate district of California show that montmorillonite is the dominant clay mineral, and that illite is abundant in red siltstones, common in green and gray borate-barren claystones, and sparse in borate-bearing rocks. Kaolinite is present only in red siltstones. The distribution of clay minerals is related to the geologic history of borate deposition.     

Chlorine-36 dating of saline sediments: preliminary results from searles lake, california

Measurements have been made of the ratios of chlorine-36 to chlorine in five halite samples from Searles Lake sediments, previously dated by carbon-14, thorium-230, and magnetostratigraphic techniques. The ages calculated from the chlorine ratios are generally concordant with those from the other methods, implying the constancy of the chlorine input ratio over the last million years.     

Uranium series dating of human skeletal remains from the del mar and sunnyvale sites, california

Uranium series analyses of human bone samples from the Del Mar and Sunnyvale sites indicate ages of 11,000 and 8,300 years, respectively. The dates are supported by internal concordancy between thorium-230 and protactinium-231 decay systems. These ages are significantly younger than the estimates of 48,000 and 70,000 years based on amino acid racemization, and indicate that the individuals could derive from the population waves that came across the Bering Strait during the last sea-level low.     

Olmec civilization, veracruz, Mexico: dating of the san lorenzo phase

Archeological excavations at San Lorenzo Tenochtitlan, Veracruz, show that the Olmec sculptures of this zone are associated with the San Lorenzo phase, which can be placed in the Early Formative period (1500-800 B.C.) on the basis of ceramic comparisons. Five of six radiocarbon dates for the San Lorenzo phase fall within the 1200-900 B.C. span. The San Lorenzo phase therefore marks the beginning of Olmec civilization, and the sites forming the San Lorenzo Tenochtitlan group represent the oldest civilized communities known in Mexico or Central America.     

Arsenic(III) fuels anoxygenic photosynthesis in hot spring biofilms from Mono Lake, California

Phylogenetic analysis indicates that microbial arsenic metabolism is ancient and probably extends back to the primordial Earth. In microbial biofilms growing on the rock surfaces of anoxic brine pools fed by hot springs containing arsenite and sulfide at high concentrations, we discovered light-dependent oxidation of arsenite [As(III)] to arsenate [As(V)] occurring under anoxic conditions. The communities were composed primarily of Ectothiorhodospira-like purple bacteria or Oscillatoria-like cyanobacteria. A pure culture of a photosynthetic bacterium grew as a photoautotroph when As(III) was used as the sole photosynthetic electron donor. The strain contained genes encoding a putative As(V) reductase but no detectable homologs of the As(III) oxidase genes of aerobic chemolithotrophs, suggesting a reverse functionality for the reductase. Production of As(V) by anoxygenic photosynthesis probably opened niches for primordial Earth's first As(V)-respiring prokaryotes.