Taphonomy and abundance of birds from the Lower Eocene Fur Formation of Denmark

The pattern, pace and extent of the evolutionary radiation of modern birds (Neornithes) by the end‐Cretaceous (65 Ma) has long been debated. Well‐dated, taphonomically understood and phylogenetically constrained fossil birds from both sides of the Cretaceous–Paleogene (K–Pg) boundary are required to quantify the shape of this radiation, but have largely been lacking. Here we report on a large collection of fossil birds from the Lower Eocene of Denmark (ca. 54 Ma) that includes three‐dimensionally preserved, articulated specimens from carbonate concretions as well as skeletal imprints and feathers. These birds are from a marine diatomite sequence (the Fur Formation), a low‐energy deep‐water preservational environment unique to the Cretaceous and Paleogene avian fossil record. We present taphonomic and palaeoecological information gleaned from these birds that in combination with phylogenetic data have implications for unravelling avian survivorship across the K–Pg boundary as well as for the pattern of the neornithine evolutionary radiation. Copyright © 2009 John Wiley & Sons, Ltd.     

An efficient discontinuous Galerkin method for advective transport in porous media

We consider a discontinuous Galerkin scheme for computing transport in heterogeneous media. An efficient solution of the resulting linear system of equations is possible by taking advantage of a priori knowledge of the direction of flow. By arranging the elements in a suitable sequence, one does not need to assemble the full system and may compute the solution in an element-by-element fashion. We demonstrate this procedure on boundary-value problems for tracer transport and time-of-flight.     

Fast computation of arrival times in heterogeneous media

We continue the work that was initiated in (K. H. Karlsen, K.-A. Lie, and N. H. Risebro. A fast marching method for reservoir simulation. Comp. Geo., 4(2) (2000)185–206) on a marching method for simulating two-phase incompressible immiscible flow of water and oil in a porous medium. We first present an alternative derivation of the marching method that reveals a strong connection to modern streamline methods. Then, through the study of three numerical test cases we present two deficiencies: (i) the original marching algorithm does not always compute the correct solution of the underlying difference equations, and (ii) the method gives largely inaccurate arrival times in the presence of large jumps within the upwind difference stencil. As a remedy of the first problem, we present a new advancing-front method, which is faster than the original marching method and guarantees a correct solution of the underlying discrete linear system. To cure the second problem, we present two adaptive strategies that avoid the use of finite-difference stencils containing large jumps in the arrival times. The original marching method was introduced as a fast tool for simulating two-phase flow scenarios in heterogeneous formations. The new advancing-front method has limited applicability in this respect, but may rather be used as a fast and relatively accurate method for computing arrival times and derived quantities in heterogeneous media.     

Early Palaeozoic tectonothermal events in basement complexes of the eastern Greywacke Zone (Eastern Alps): evidence from U–Pb zircon data

Field observations and U-Pb zircon data yield evidence that the Kaintaleck Complex represents a distinct crystalline basement unit of the eastern Greywacke Zone and contrasts partly with other pre-Alpine basement complexes of the Eastern Alps. The age data indicate possible Late Archean rock formation, several magmatic and metamorphic events in the Early Palaeozoic (ca. 520-490 and ca. 400-360 Ma), and low-grade metamorphic overprint in the Cretaceous. Zircons from a garnet gneiss layer in a plagioclase gneiss and amphibolite sequence yield an upper intercept age of ca. 2.55 Ga which is interpreted as a possible protolith age. The lower intercept age at 514 Ma represents either (1) a magmatic event or (2) a metamorphic overprint within amphibolite facies conditions. Magmatic zircons derived from granitic orthogneiss boulders of the Kalwang Conglomerate, which covers the crystalline basement, crystallised at ca. 500 Ma. The lower discordia intercepts of the orthogneiss boulders mark the Cretaceous low-grade metamorphic overprint. The lower intercept age of paragneiss zircons from another slice of the Kaintaleck Complex suggests a likely Devonian metamorphic event at ca. 390-400 Ma. The new data demonstrate that the Kaintaleck Complex experienced several stages of tectonothermal evolutions, which are in contrast to the evolution of the main mass of the Austroalpine basement. The data constrain linkages of this part of the Austroalpine basement to the Cordillere Ligérienne and Cadomian block within West-European Variscides.     

Wind-determined sediment distribution and Holocene sediment yield in a small,Danish, kettle lake

Sediment distribution was mapped by multiple corings in a small oligotrophic lake in northwestern Denmark. Sediment cores along a representative West-East transect were dated by ¹⁴C and correlated using pollen, mineral magnetics and general lithology. Estimates of whole-lake Holocene sediment accumulation were used to calculate sediment yield (terrestrial erosion). Results indicate that: 1) sediment yield was low 10000–5000 BP and increased strongly 5000–2500 BP and again 2500–1200 BP, 2) sediment focusing and waves and currents induced by strong winds were the major processes controlling sediment distribution throughout the Holocene; 3) the dominant wind direction of strong winds has been westerly throughout the Holocene; and 4) the lake was probably more productive in the last 5000 years than in the period from 10000 to 5000 BP.     

The sedimentary record of spheroidal carbonaceous fly-ash particles in shallow Danish lakes

Spheroidal carbonaceous particles (SCP) from combustion of oil and coal have been quantified in cores from top sediments of Danish shallow lakes. Chronologies were provided by ²¹⁰Pb-dating supplemented by measurements of other radionuclides (¹³⁷Cs, ¹³⁴Cs, ²⁴¹Am). All cores show indications of sediment mixing but most still retain a characteristic SCP record. Deposition rates of SCP were low until the 1920s, increased strongly after World War II, reached maximum levels around 1970 and decreased thereafter. These results were used to infer a new chronology for a sediment core from a shallow lake, from which a ²¹⁰Pb chronology had previously been published.SCP inventories are positively correlated with ²¹⁰Pb inventories and dry matter accumulated since 1900, suggesting that absolute SCP accumulation rates may be more influenced by sedimentary processes than by atmospheric fluxes. The concentrations of SCP in surface sediments of the six lakes do, however, correlate with regional SO₂ emissions.     

A Simple Method for Measuring the Vertically of Small-Diameter Driven Wells

The presence of stones, solid waste, and other obstructions can deflect small-diameter driven wells during installation, leading to deviations of the well from its intended position. This could lead to erroneous results, especially for measurements of ground water levels by water level meters. A simple method was developed to measure deviations from the intended positions of well screens and determine correction factors required for proper measurement of ground water levels in nonvertical wells. The method is based upon measurement of the hydrostatic pressure in the bottom of a water column, which is established in the well lube. The method was used to correct water level measurement in wells driven through a landfill site. Errors of up to 27 cm in water level were observed at the landfill site. The correction of the water level measurements had a significant effect on estimated local ground water flow directions.     

On the origin of saline fluids in the KTB (continental deep drilling project of Germany)

Highly saline fluids were encountered during the German Continental Deep Drilling Project (KTB) from depths ranging between 2 and 3 km to about 9 km. The most reliable data were obtained from samples extracted during a long-term pumping test in the 4000-m deep KTB pilot hole. Some 460 m³ CaNaCl brines with about 68 g l⁻¹ total dissolved solids (TDS) and some 270 m³ associated gases, mainly N₂ and CH₄ were pumped to the surface from the main fracture system situated near the bottom of the pilot hole. Geochemical and isotopic data support the hydraulic tests which suggest the presence of an open and large fluid reservoir at depth. The pumped fluids from this main fracture system were released from a deep reservoir situated at more than 5500 m depth which is hydraulically connected with the 9101 m deep KTB main hole, drilled some 250 m to the northeast of the pilot hole.While Ca and Sr contents of the extracted brines may be the result of water-rock interaction, Cl is most likely of external origin. The Cl is hypothesized to derive from geotectonic processes rather than to descending infiltration of paleo-seawater (evaporitic brines). The sampled fluids have probably migrated from a deeper reservoir to their present position since the Cretaceous-Tertiary period due to tectonic activity. However, several isotopic studies have identified an admixture of descending paleowaters down to more than 4000 m depth. The high ³⁶ClCl ratio of the fluids sampled during the long-term pumping test point to a host rock highly enriched in UTh, unlike the sampled KTB country rocks. The fluid reservoir is believed to be in contact with the Falkenberg granite massif situated about 2 km to the E of the KTB holes capable of supplying sufficient neutron flux for considerable subsurface production of 36C1. The NaCl(K, SO₄) precursor fluids of the CaNaCI brines were produced in the course of extensive tectonic processes since the Late Caledonian within the Bohemian Massif.     

Am improved source mechanism for the 1935 Timiskaming,Quebec earthquake from regional waveforms

The Timiskaming earthquake, which occurred near the Quebec-Ontario border at the northwest end of the Western Quebec seismic zone in 1935, is one of the five largest instrumentally recorded southeastern Canadian earthquakes. Previous studies of this earthquake concentrated on modeling teismograms recorded at regional distances, a better constrained focal mechanism is obtained. The waveforms indicate thrust faulting on a moderately dipping northwest striking plane at a depth of 10 km. TheM _w of 6.1 determined in this study is in good agreement with previous magnitude estimates (m _b 6.1,M _s 6.0, andm _bLg 6.2–6.3). The focal mechanism is similar to those of many recent small to moderate earthquakes in the region, and the inferred (from theP axis) acting stress of northeast compression is consistent with the overall eastern North American stress field. The Lake Timiskaming Rift Valley in which the earthquake occurred, comprises several northwest striking faults consistent with the strike of the 1935 event. Thus, the 1935 earthquake appears to be a result of faulting on the reactivated Timiskaming graben.