RADIOCARBON DATING OF A PEAT DEPOSIT IN THE CUCAMONGA FAULT ZONE,CALIFORNIA*

A sequence of peat beds was deposited in a small sag pond along the Cucamonga fault zone during late Holocene. The stratigraphic section of this deposit is described; several beds have been radiocarbon dated. Comparison of radiometric and stratigraphic chronologies allows reconstruction of the geomorphic history of the sag pond, which extends back 3000 years, and establishes evidence that the fault has been active within the very recent geologic past.     

The Greenwell Springs LL4 Chondrite: A New Fall from Louisiana,USA

Abstract— A 664 gm stone fell into suburban Baton Rouge in November 1987. The stone has a nearly complete fusion crust and was undamaged upon impact. The ordinary chondrite contains equilibrated olivine, Fa₂₈, and largely equilibrated bronzite, Fs₂₃. Some bronzite is still compositionally zoned and polysynthetically twinned, thus requiring petrologic classification of the meteorite as a type 4. A major element analysis of the meteorite falls exclusively into the field for the LL compositional group.     

Calculation of the added mass of elliptical cylinders with vertical fins in shallow water

In order to carry out any studies of ship motions, concerning either seakeeping or manoeuvring, it is usually necessary to have knowledge of the added mass of the hull section shapes. In deep water, the added mass can be found using conformal mapping techniques combined with residue calculus, or by means of surface singularity distributions. In shallow water, the need to utilise an infinite number of mirror images, to represent the effects of the seabed and the free surface, precludes the use of the deep-water methods in this case. In previous papers, the author presented methods to evaluate the added mass of semi-circular and elliptical body sections. Now, using a similar Schwarz–Christoffel method, the added mass of elliptical body sections with vertical fins in shallow water is evaluated.     

Spatial Differences in Multi-Resolution Urban Automata Modeling

The last decade has seen a renaissance in spatial modeling. Increased computational power and the greater availability of spatial data have aided in the creation of new modeling techniques for studying and predicting the growth of cities and urban areas. Cellular automata is one modeling technique that has become widely used and cited in the literature; yet there are still some very basic questions that need to be answered with regards to the use of these models, specifically relating to the spatial resolution during calibration and how it can impact model forecasts. Using the SLEUTH urban growth model ( Clarke et al. 1997 ), urban growth for San Joaquin County (CA) is projected using three different spatial grains, based on four calibration routines, and the spatial differences between the model outputs are examined. Model outputs show that calibration at finer scaled data results in different parameter sets, and forecasting of urban growth in areas that was not captured through the use of more coarse data.     

Estimating secondary production and benthic consumption in monitoring studies: A case study of the impacts of dredged material disposal in Galveston Bay, Texas

We examined the effects of dredged material disposal on benthic macroinvertebrates in Galveston Bay, Texas, USA, while investigating the utility of estimating secondary production with estimation methods that have less rigorous data requirements than most classical techniques. Production estimates were compared to estimates of benthic consumption by blue crabs, shrimp, and epibenthic fish. There was no evidence that dredged material disposal had a detrimental impact on benthic production; however, production was low throughout the entire bay the year following dredged material disposal, which may have obscured an assessment of the impact of disposal. In fact, disposal sites yielded both the highest production estimates and species richness in both the upper and lower bay areas 2 yr after disposal. Of the five estimation methods used, two that incorporated environmental parameters (temperature and depth) yielded similar and moderate results, ranging from 1.1 g ash-free dry weight m² yr¹ to 26.9 g ash-free dry weight (AFDW) m^?2 yr^?1 over the 4 yr studied. Daily food ration estimates applied to fishery-independent trawl-survey data yielded overall benthic consumption estimates ranging from 1.1 g AFDW m^?2 to 1.7 g AFDW m^?2. A second method of estimating consumption, which used transfer efficiency estimates and annual fisheries statistics produced slightly lower benthic consumption estimates (0.72–1.13 g AFDW m^?2). The average consumption estimate exceeded benthic production in the upper bay in one of the 4 yr for which benthic production was estimated. In years with high benthic production, the estimated benthic food requirement of epibenthic predators was roughly 10–15% of benthic production. Variation in annual benthic production estimates was two to three times greater than the variation in consumption estimates.     

The Principal Point and CCD Cameras

The principal point has long been regarded as one of the fundamental parameters in camera calibration. In the age of film based aerial and large format terrestrial cameras, the principal point could be located by a variety of techniques with a certainty of ±10 mm (Carman and Brown, 1961) and this was considered sufficient. However, aerial cameras were precision, purpose built, expensive pieces of equipment where the assembly was painstaking and the location of the principal point measured to a known tolerance. In the digital era, photogrammetrists, and many others, are using cameras which have not been specifically designed or built for photogrammetry. For these cameras there is no requirement for the manufacturers to position the lens in a pre-defined location relative to the image sensing plane or for the lens manufacturer to align the lens elements precisely. In fact, deviations from the centre of the sensor can be a considerable percentage of the extent of the sensor (up to 10 per cent for some zoom lenses (Burner, 1995)). This paper discusses the development of methods of obtaining the location of the principal point, considers the relationship between the principal point and other parameters in the functional model, and shows how the location of this point can be estimated with and without recourse to autocollimation methods.     

A new potassium-iron-nickel sulphide from a nodule in kimberlite

A new K-rich sulphide phase is described from a clinopyroxene-ilmenite intergrowth from the Frank Smith kimberlite diatremes. The mineral occurs as ovoid blebs, which also contain pyrrhotite and pentlandite, in close spatial association with the ilmenite lamellae, and as individual grains in cracks in the clinopyroxene host. Chemical analyses from twelve grains show the following ranges of composition (wt.%): K, 8.12–13.01; Cu, 1.24–2.99; Fe, 38.47–41.76; Ni, 11.65–15.04; S, 32.09–34.34. Electron diffraction data indicate a primitive cubic unit cell,a = 10.29 ± 0.03Å, with no systematically absent reflections. Three models for the origin of this sulphide, liquid immiscibility, multiple exsolution, and metasomatism, are considered. The discovery of potassic sulphide in a kimberlite nodule has important implications, not only as a potential source of K in the upper mantle, but also for those models which propose removal of K and S from the lower mantle into the core.     

Excess 3He in deep water on the East Pacific Rise

Helium isotope measurements show that water on the crest and flanks of the East Pacific Rise has the highest enrichment in ³He so far observed in the oceans; the ³He/⁴He ratio anomaly relative to atmospheric helium is + 32% at the mid-depth maximum in the profiles. The corresponding ³He solubility anomaly relative to saturation with atmospheric helium is +50%. These data indicate that active sea-floor spreading sites on the crests of the mid-ocean rises are the sources of primordial helium injected into the ocean from the earth's interior. The ³He/⁴He ratio in this flux is approximately 1.6 × 10^?5, about 11 times the atmospheric ratio of 1.4 × 10^?6. The total flux of ³He into the atmosphere is 4.6 atoms cm^?2 earth-surface sec^?1, most of which (4.0 atoms cm^?2 sec^?1) is supplied by the oceanic flux. The corresponding atmospheric residence time for ³He is 10⁶ years, which, within the large uncertainties of supply and demand (thermal escape), is consistent with the requirement for a steady state.     

Stratigraphy,paleontology, and age of Lake Algonquin sediments in southwestern Ontario,Canada

Molluscs, ostracodes, diatoms, pollen, plant macrofossils, peat, and wood have been found in glacial Lake Algonquin sediments, and estuarine-alluvial sediments of the same age, in southern Ontario. Molluscs and ostracodes are particularly abundant and widespread. Pollen analysis of Lake Algonquin sediments, bogs on the Algonquin terrace, and upland bogs above the Algonquin terrace, indicate that Lake Algonquin was still in existence at the time of the spruce-pine pollen transition, previously dated at an average of 10,600 yr BP at a number of sites in Michigan, Ohio, and southern Ontario. Wood in estuarine-alluvial sediments graded to the Algonquin level is of similar radiocarbon age. Evidence from several sites in the eastern Great Lakes area suggests the presence of a preceding low-water stage (Kirkfield outlet stage); drowned and alluviated valleys and fining-upward sediment sequences have been identified in this study as further supporting evidence. Lake Algonquin drained from the southern sites by isostatic tilting and eventual opening of the “North Bay outlet” some time shortly after 10,400 yr BP.Our radiocarbon dates suggest the low-water stage has an age of about 11,000 yr BP, and that Lake Algonquin drained 10,000–15,000 y. a. Dates previously published for the Lake Michigan basin are generally too young in comparison with ours, and dates on the Champlain Sea are generally too old. More critical evaluation of all dating results is desirable.From fossil remains we suggest a rapidly expanding fauna in the waters of Lake Algonquin. The spruce pollen period was a time of rapid faunal and floral migration, when the ice front was retreating from Kirkfield to North Bay, Ontario. Diversity of some species and fossil numbers increased substantially at the transition from spruce to pine just before Lake Algonquin drained.