Concentrations of organic carbon, carbon isotopes (13C and 14C), atmospheric 10Be in soil, and in situ 10Be in bedrock and weathering rock were determined in a study of a profile of a grassland slope at the Heshan Hilly Land Interdisciplinary Experimental Station, Chinese Academy of Sciences, in Guangdong Province, China. A good linear relationship between depth and the 14C apparent age of the organic carbon demonstrates that the rock weathering process and the accumulation process of organic matter in the slope are relatively stable. Both 14C and 10Be results show that about 34% of soil in the grassland slope has been eroded during the past 3800 yr. The 10Be results for interstitial soil from weathered rocks show that the 90-cm-thick weathering rock layer above the bedrock has evolved over a period of 1.36 Myr. The concentrations of in situ 10Be in the weathered rock and bedrock are 10.7 X 10^4 atoms/g and 8.31 X 10^-4 atoms/g, respectively. The weathering rate of the bedrock, equivalent to the soil production rate, was estimated at 8.8 X 10^-4 cm/yr, and the exposure ages of the weathered rock and the bedrock were 72 kyr and 230 kyr, respectively.

Soil gas samples were obtained from the unsaturated zone at eight sites in the Great Plains. Three of these sites were sampled extensively for gas composition and carbon isotopes. Sampling equipment consisted of a nest of gas probes vertically spaced by roughly 3m at most sites, generally approaching the water table. Water wells, 10cm in diameter, were screened in the topmost layer groundwater. Inverted cattle tanks were used to collect CO2 samples from the soil surface. The major gas components were analyzed with emphasis on CO2, Delta--13C, and 14C measurements. The same components were studied in groundwater samples. Higher than atmospheric CO2 concentrations were found in all soil samples. Root respiration and oxidation of organic matter were sources for the additional CO2. When lignite was present in the unsaturated zone, gaseous oxygen reacted almost completely, and CO2 levels rose to 19%. Near the surface, annual cycles in total CO2, Delta--13C, and 14C were observed. 14C activities were close to present post-bomb levels at the surface and generally declined with depth. At some sites, oxidation of lignite caused decline of 14C levels to 1 or 2% of their surface value at 8m depth. Without lignite, the 14C activity remained above 50% at all depths. Concentrations of total carbon and its isotopes in ground water remained very stable throughout the study. This implies that geochemical processes in the aquifer vary on time scales longer than the seasonal effects observed in the near-surface unsaturated zone.

Research was initiated at the Texas Experimental Ranch in 1981 to quantify the effects of 2 stocking densities, equivalent to 14- and 42-paddock rotational grazing (RG) treatments, on aboveground biomass dynamics, aboveground net primary production (ANPP), and harvest efficiency of forage. Baseline data were collected in 1981 from 3 adjacent 30-ha paddocks in a 14-paddock, cell designed RG treatment. Near the beginning of the 1982 growing season the center paddock was subdivided into three, 10-ha paddocks to establish the RG-42 treatment. Stocking densities in the 14- and 42-paddock treatments were 4.2 and 12.5 AU/ha, respectively, from March 1982 to June 1984 and 3.0 and 9.1 AU/ha from June to November 1984. During 1981, estimated ANPP in the two RG-14 paddocks averaged 4,088 kg/ha as compared to 5,762 in the single RG-42 paddock. Following subdivision, ANPP in the RG-14 paddocks averaged 2,533 kg/ha as compared to 2,670 kg/ha in the RG-42 paddocks. Although ANPP varied significantly among the 4 years of the study it was not affected by density treatment. Likewise, harvest efficiency varied among years but was unaffected by density treatment. Average harvest efficiency over the 4 years was about 42%. Aboveground biomass dynamics were also generally unaffected by density treatments.

Pachacamac, covering an area of about 600 hectares (ha) near the Pacific shore, is one of the largest and most important archaeological sites in Peru. Most of the monumental adobe-made buildings of the later pre-Inca period (or Late Intermediate Period, about 10th-15th century AD) are so-called pyramids with ramps (the role of the ramps has been interpreted in different ways). Precise dating of the pyramids appears as a crucial step in defining the functions of Pachacamac in pre-Inca times. In this paper, we present the results obtained from 3 field campaigns at Pyramid III, one of the biggest buildings of the site. A total of 24 radiocarbon datasets from 4 different laboratories will help us to place the various steps of development of Pyramid III on a timescale, defined on the basis of the excavations. More absolute dates are available from another pyramid with ramps, which allow us to make comparisons and propose a new model of interpretation for the Pachacamac site during the Late Intermediate Period (LIP).

Sediment from Lake Boeckella, Antarctic Peninsula, is richer in Ca, Cd, Cu, P, Sr and Zn than that of six other lakes in the area. The elements originate from Adélie penguin (Pygoscelis adeliae) guano on the lake shores. Changing Cu and P concentrations in the lake sediment are used as a proxy for penguin influence on the lake sediment from ca. 5850 BP to Present. A 14C dating model suggests that the 14C correction factor in the lake sediments depends on the penguin proxy, the apparent age of the penguin guano and the amount of particulate carbon originating from the carbon-bearing shales in the watershed. Glacial meltwater and dissolved carbonates do not contain enough "old" carbon to contribute significantly to the correction factor. Ages corrected with the 14C dating model agree with the depth vs. age curve based on independently 14C-dated tephra horizons. The reservoir effect has been constant since at least 5800 BP, implying long-term stability of the currents and water masses in the area. The existing chronology for Lake Boeckella has been recalculated. The period of glacial advance, previously thought to have culminated at 5000 BP, is now thought to have culminated at 4700 BP; deglaciatlon of the area is thought to have occurred at 6300 BP instead of 8680 BP.

Basal 14C dates from a core of the mire at Puerto del Hambre (53 degrees 36'21"S, 70 degrees 55'53"W), located within the area of glaciation in Estrecho de Magallanes-Bahia Inutil, Chile, are no older than 14,455 +/115 yr BP. The 14C dates are on samples from which screening isolated autochthonous plant remains. Previous 14C dates of 15,800 +/200, 16,590 +/320, and 16,290 +/140 yr BP are from bulk samples collected from similar basal increments at the site during 3 separate, independent coring operations. The previous suite of 14C dates was suspected to be contaminated by older carbon in the light of chronological evidence, which indicates a 14C age of approximately 14,850 yr BP for glaciation elsewhere in southern Chile. Contamination by "infinitely old" carbon reworked from nearby Tertiary beds and redeposited at Puerto del Hambre is evidently the cause for the older 14C dates.