The search for fullerenes in rocks from the Ries impact crater

Abstract— Since their discovery, fullerenes have been reported from various geological environments. One group of these findings has been related to bolide impacts, e.g., the Sudbury crater and the K‐T and P‐T boundaries. Impact rocks of the Ries crater, Germany, including samples of suevites, metamorphosed crystalline clasts, and glass bombs, have been collected in the Otting, Altebürg, and Seelbronn quarries. No fullerenes in concentrations above 1 ppb have been found in analyzed samples. Laser desorption time‐of‐flight mass spectrometry (LD‐TOF‐MS) confirmed the absence of fullerenes in the analyzed samples. These results support the concept that the Ries impactor was a stony meteorite.     

Glacial lake levels and Eastern Great Lakes Palaeo‐Indians

This article investigates changing lake levels in the late Pleistocene eastern Great Lakes in order to gain insights into the Early Palaeo‐Indian occupations. Significant new information bearing on lake level history is provided, notably the first well‐documented deposits of a high water level above modern in the ca. 11,000–10,300 B.P. period in the southern Lake Huron basin. The lake level information, along with paleoenvironmental and site data, reinforces site age estimates to the 11th millennium B.P.; suggests significant numbers of sites have been inundated by rising water levels; provides specific information on the setting of archaeological sites such as placing the Parkhill site adjacent to a large lake estuary; indicates reasons for the attractiveness of shorelines to Palaeo‐Indians including persistence of more open areas conducive to higher game productivity; and points to ideal areas for future archaeological site survey, particularly in the Lake Erie drainage. © 2000 John Wiley & Sons, Inc.     

The Permian-Triassic boundary event: a geochemical study of three Chinese sections

Trace elements were determined in two well-documented Chinese Permian-Triassic (P/Tr) boundary sections (Meishan and Shangsi) and in a new section (Liangfenya). Iridium concentrations range from 3 to 87 pg/g, at or below levels in common sedimentary rocks. The results contrast with previous reports of high Ir concentration in the Meishan and Shangsi sections and offer no support to suggestions of a major meteoroid impact at the end of the Permian. A notable feature in each of these widely separated P/Tr sections (500–1500 km) is the existence of 2–5 light-colored clay layers at and near the boundary. These clay layers are strongly enriched in Cs, Zr, Hf, Ta, and Th and depleted in Cr, Co, and Ir, indicating that they are altered ash, apparently from the same massive silicic volcanic eruptions. We estimate the magnitude of these eruptions to be a few thousand km³ of magma, a volume comparable to the great Toba eruption.     

AMS radiocarbon dating of organic fractions from varved lake sediments: an empirical test of reliability

Replicate cores of annually laminated (varved) sediments have been used to test the accuracy and precision of chronologies of lake sediment accumulation over the last 1000 years, based on AMS 14C measurements. The internally consistent results show that in the case of the soft-water lake sediments studied (Kassjön, northern Sweden), all the organic fractions that include aquatic components give significantly older dates than expected. Only the single terrestrial macrofossil and the fine, unidentified residual particulate fraction provide dates close to the true age of the sediments. The results also show that age discrepancies for some fractions are not constant over time. The age discrepancies may arise from some carbon reservoir effect within the aquatic ecosystem, from resuspension and focusing of older marginal organic material into the deepest part of the lake or from some combination of these processes. More work is needed on the 14C age of organic fractions in varve-dated sediments from a range of lake types.     

Hatton Bank (northwest U.K.) continental margin structure

Summary. The continent-ocean transition near Hatton Bank was studied using a dense grid of single-ship and two-ship multichannel seismic (mcs) profiles. Extensive oceanward dipping reflectors in a sequence of igneous rocks are developed in the upper crust across the entire margin. At the landward (shallowest) end the dipping reflectors overlie continental crust, while at the seaward end they are formed above oceanic crust. Beneath the central and lower part of the margin is a mid-crustal layer approximately 5 km thick that could be either stretched and thinned continental crust or maybe newly formed igneous crust generated at the same time as the dipping reflector sequence. Beneath this mid-crustal layer and above a well defined seismic Moho which rises from 27 km (continental end) to 15 km (oceanic end) across the margin, the present lower crust comprises a 10–15 km thick lens of material with a seismic velocity of 7.3 to 7.4 km/s. We interpret the present lower crustal lens as underplated igneous rocks left after extraction of the extruded basaltic lavas, A considerable quantity of new material has been added to the crust under the rifted margin. The present Moho is a new boundary formed during creation of the margin and cannot, therefore, be used to determine the amount of thinning.     

A GCM study of future climate response to aerosol pollution reductions

We use the global atmospheric GCM aerosol model ECHAM5-HAM to asses possible impacts of future air pollution mitigation strategies on climate. Air quality control strategies focus on the reduction of aerosol emissions. Here we investigate the extreme case of a maximum feasible end-of-pipe abatement of aerosols in the near term future (2030) in combination with increasing greenhouse gas (GHG) concentrations. The temperature response of increasing GHG concentrations and reduced aerosol emissions leads to a global annual mean equilibrium temperature response of 2.18 K. When aerosols are maximally abated only in the Industry and Powerplant sector, while other sectors stay with currently enforced regulations, the temperature response is 1.89 K. A maximum feasible abatement applied in the Domestic and Transport sector, while other sectors remain with the current legislation, leads to a temperature response of 1.39 K. Increasing GHG concentrations alone lead to a temperature response of 1.20 K. We also simulate 2–5% increases in global mean precipitation among all scenarios considered, and the hydrological sensitivity is found to be significantly higher for aerosols than for GHGs. Our study, thus highlights the huge potential impact of future air pollution mitigation strategies on climate and supports the need for urgent GHG emission reductions. GHG and aerosol forcings are not independent as both affect and are influenced by changes in the hydrological cycle. However, within the given range of changes in aerosol emissions and GHG concentrations considered in this study, the climate response towards increasing GHG concentrations and decreasing aerosols emissions is additive.