Use of Fossil Bryozoans in Sourcing Lithic Artifacts

This study reviews the occurrence and potential of bryozoans within lithic artifacts and also sets out a methodology for their use in sourcing and discusses the advantages and disadvantages of this approach. We present case studies from our own research and from the literature on using bryozoans in sourcing archaeological lithic artifacts. Fossil bryozoans of different ages and clades can be effectively used to determine the material source of lithic artifacts from a variety of prehistoric ages. The case studies included in this report span the stratigraphic range of bryozoans from the Ordovician to the Neogene. The bryozoans came from four different orders: trepostome, fenestrate, cyclostome, and cheilostome. The use of these lithic artifacts ranged back to 25 ka. Although the majority of the fossil bryozoans were incidental in the artifacts, the bryozoans were still useful for determining their original source rock. The improved searchable online paleontologic databases allow for more efficient use of fossil bryozoans to constrain the stratigraphic and paleogeographic distribution of source outcrops. Although generally underutilized in sourcing prehistoric lithic artifacts, it is clear that by analyzing bryozoans, an increased understanding of the lithologic nature of these materials could be gained by the archaeological community.     

The Potassium‐Argon Laser Experiment (KArLE): In Situ Geochronology for Planetary Robotic Missions

Geochronology is a fundamental measurement for planetary samples, providing global and solar system context for the conditions prevailing on the planet at the time of major geological events. The potassium (K)‐Argon (Ar) laser experiment (KArLE) will make in situ noble gas geochronology measurements aboard planetary robotic missions such as rovers and landers. Laser‐induced breakdown spectroscopy (LIBS) is used to measure the K abundance in a sample and to release its noble gases; the evolved Ar is measured by mass spectrometry, and relative K content is related to absolute Ar abundance by sample mass, determined by optical measurement of the ablated volume. This approach allows K and Ar to be measured on identical volumes multiple times to create an isochron, which improves the age determination and reveals irregularities in the rock if they exist. The KArLE technique measures a whole‐rock K‐Ar age with 10% uncertainty or better for rocks 2 Ga or older, sufficient to resolve the absolute age of many planetary samples. The LIBS–mass spectrometry approach is attractive because the analytical components have been flight‐proven, do not require further technical development and provide essential measurements (complete elemental abundance, evolved volatile analysis, micro‐imaging) as well as in situ geochronology.     

Source, sea level and circulation effects on the sediment flux to the deep ocean over the past 15 ka off eastern New Zealand

The last post-glacial transgression and present highstand of sea level were accompanied by a reduction in the terrigenous flux to the deep ocean bordering the active convergent margin off the eastern North Island of New Zealand. Although in accord with long-established models of highstand shelf deposition, new data from giant piston core MD97 2121 (2314 m depth) reveal that the flux also varied with terrigenous supply and palaeocirculation. Between 15 and 9.5 ka, the flux reduced from 33 to 20 g/cm²/ka as supply declined with an expanding vegetation cover, and mud depocentres became established on the continental shelf. An increase from 20 to 27 g/cm²/ka during 9.5–3.5 ka coincided with a strengthened East Cape Current which probably introduced sediment from fluvial and shelf sources in the north. The flux profile shows no immediate response to the establishment of modern sea level 7 ka. However, accumulation decreased from 3.5 to 1 ka as more sediments were retained on the shelf, possibly under wind-strengthened, along-shelf currents. Over the last 1 ka, the flux decline halted under increased terrigenous supply during anthropogenic development of the land.Despite the proximity of the North Island's Central Volcanic Region, major eruptions caused only brief increases (centuries duration) in the terrigenous flux through direct deposition of airfall and possibly fluvial redistribution of onshore volcanic deposits. Frequent earthquakes also had little short-term effect on accumulation although such events, along with volcanism, probably contribute to the long-term high flux of the region.The other measured flux component, biogenic carbonate, reached maxima of 6 g/cm²/ka between 11 and 8.5 ka when nutrient-bearing waters of the East Cape Current dominated the palaeoceanography. After these peaks, carbonate accumulation declined gradually to modern levels of 3 g/cm²/ka.     

Summer larval fish assemblages in the Southern Tyrrhenian Sea (Western Mediterranean Sea)

The purpose of this paper was to study the community structure, in terms of species composition, abundance and spatial distribution, of fish larvae in a wide coastal area of Sicily facing the Southeastern Tyrrhenian Sea, extending for 2300 km² from Cape Cefalù to the west, to Cape Rasocolmo in the east. This study analyses how species are assembled in relation to an inshore–offshore gradient and also how environmental conditions, determined by surface circulation patterns occurring in the Central Mediterranean at the local scale, determine the distribution patterns. Samples from 39 stations were collected using a 60‐cm Bongo net during an ichthyoplanktonic survey carried out in June 2006. In all, 62 taxa, representing 32 families, were identified. Cyclothone braueri (59.6%), Engraulis encrasicolus (9.2%) Lampanyctus crocodilus (4.3%) and Lampanyctus pusillus (4.1%) were the most abundant species. The results showed that the highest abundance value (14830.6 fish larvae per 10 m² sea surface) was observed in the western part of the study area. MDS, SIMPER and CCA analyses revealed well defined groups of stations and assemblages of larvae in accordance with an inshore–offshore gradient. The results of this study could have implications for the management of marine resources because the investigated area has already been identified as a nursery area for many pelagic and coastal fishes and a natural habitat for many species of high commercial interest.     

Comment on: “New” lunar meteorites: Impact melt and regolith breccias and large‐scale heterogeneities of the upper lunar crust,by P. H. Warren,F. Ulff‐Møller,and G. W. Kallemeyn

Abstract We described lunar meteorite Dhofar 026 (Cohen et al. 2004) and interpreted this rock as a strongly shocked granulitic breccia (or fragmental breccia consisting almost entirely of granulitic‐breccia clasts) that was partially melted by post‐shock heating. Warren et al. (2005) objected to many aspects of our interpretation: they were uncertain whether or not the bulk rock had been shocked; they disputed our identification of the precursor as granulitic breccia; and they suggested that mafic, igneous‐textured globules within the breccia, which we proposed were melted by post‐shock heating, are clasts with relict textures. The major evidence for shock of the bulk rock is the fact that the plagioclase in the lithologic domains that make up 80–90% of the rock is devitrified maskelynite. The major evidence for a granulitic‐breccia precursor is the texture of the olivine‐plagioclase domain that constitutes 40—45% of the rock; Warren et al. apparently overlooked or ignored this lithology. Textures of the mafic, igneous‐textured globules, and especially of the vesicles they contain, demonstrate that these bodies were melted and crystallized in situ. Warren et al. suggested that the rock might have originally been a regolith breccia, but the textural homogeneity of the rock and the absence of solar wind—derived noble gases preclude a regolith‐breccia precursor. Warren et al. classified the rock as an impact‐melt breccia, but they did not identify any fraction that was impact melt.     

Methane Production and Isotopic Fingerprinting in Ethanol Fuel Contaminated Sites

Biodegradation of organic compounds in groundwater can be a significant source of methane in contaminated sites. Methane might accumulate in indoor spaces posing a hazard. The increasing use of ethanol as a gasoline additive is a concern with respect to methane production since it is easily biodegraded and has a high oxygen demand, favoring the development of anaerobic conditions. This study evaluated the use of stable carbon isotopes to distinguish the methane origin between gasoline and ethanol biodegradation, and assessed the occurrence of methane in ethanol fuel contaminated sites. Two microcosm tests were performed under anaerobic conditions: one test using ethanol and the other using toluene as the sole carbon source. The isotopic tool was then applied to seven field sites known to be impacted by ethanol fuels. In the microcosm tests, it was verified that methane from ethanol (δ¹³C = −11.1‰) is more enriched in ¹³C, with δ¹³C values ranging from −20‰ to −30‰, while the methane from toluene (δ¹³C = −28.5‰) had a carbon isotopic signature of −55‰. The field samples had δ¹³C values varying over a wide range (−10‰ to −80‰), and the δ¹³C values allowed the methane source to be clearly identified in five of the seven ethanol/gasoline sites. In the other two sites, methane appears to have been produced from both sources. Both gasoline and ethanol were sources of methane in potentially hazardous concentrations and methane could be produced from organic acids originating from ethanol along the groundwater flow system even after all the ethanol has been completed biodegraded.     

Multiplet-Multiplet Coupling Due to Lateral Heterogeneity: Asymptotic Effects On the Amplitude and Frequency of the Earth's Normal Modes

Summary. Starting with the first-order formulation of quasi-degenerate splitting theory for the normal modes of a laterally heterogeneous earth, we have obtained an asymptotic expression for the coupling terms corresponding to neighbouring multiplets along the same dispersion branch as the mode considered, valid to order 1/ℓ, where ℓ is the angular order of this mode (ℓ≥ 1).
We show that, to order zero, these coupling terms introduce a small shift in epicentral distance into the expression for the long period seismogram obtained by normal mode summation. This shift depends on the difference between the great circle and the minor arc averages of the local frequency. the coupling terms thus permit us to reconcile results obtained by normal-mode summation and by a propagating wave approach, as far as the dependence on structure of the phase of surface waves is concerned.
To order 1/ℓ, the coupling terms result in a perturbation in the amplitude of the mode considered, which depends on spatial derivatives of the local frequency and thus on the structure in the vicinity of the source station great circle path. We show that this term is equivalent to that which is found using ray perturbation methods for propagating surface waves. We compare and discuss the assumptions underlying both approaches and illustrate, by an example, the potential of the asymptotic normal-mode formulation for improved modelling of lateral heterogeneity in the earth.