Cataclysmic Late pleistocene flooding from glacial Lake Missoula: A review

Late Wisconsin floods from glacial Lake Missoula occurred between approximately 16 and 12 ka BP. Many floods occurred; some were demonstrably cataclysmic. Early studies of Missoula flooding centered on the anomalous physiography of the Channeled Scabland, which J. Harlen Bretz hypothesized in 1923 to have developed during a debacle that he named ‘The Spokane Flood’. Among the ironies in the controversy over this hypothesis was a mistaken view of uniformitarianism held by Bretz's adversaries. After resolution of the scabland's origin by cataclysmic outburst flooding from glacial Lake Missoula, research since 1960 emphasized details of flood magnitudes, frequency, routing and number.Studies of flood hydraulics and other physical parameters need to utilize modern computerized procedures for flow modeling, lake-burst simulation, and sediment-transport analysis. Preliminary simulation models indicate the probability of multiple Late Wisconsin jökulhlaups from Lake Missoula, although these models predict a wide range of flood magnitudes.Major advances have been made in the study of low-energy, rhythmically bedded sediments that accumulated in flood slack-water areas. The ‘forty floods’ hypothesis postulates that each rhythmite represents the deposition in such slack-water areas of separate, distinct cataclysmic floods that can be traced from Lake Missoula to the vicinity of Portland, Oregon. However, the hypothesis has numerous unsubstantiated implications concerning flood magnitudes, sources, routing and sedimentation dynamics.There were multiple great Late Wisconsin floods in the Columbia River system of the northwestern United States. Studies of high-energy, high altitude flood deposits are necessary to evaluate the magnitudes of these floods. Improved geochronologic studies throughout the immense region impacted by the flooding will be required to properly evaluate flood frequency. The cataclysmic flood concept championed by J. Harlen Bretz continues to stimulate exciting and controversial research.     

LEGRI Science Operation Center. Architecture and Operations

The LEGRI Science Operation Center (SOC) is the single contact pointbetween the MINISAT-01 Centro de Operaciones Científicas (COC)located at Villafranca del Castillo (Madrid) and the LEGRI Consortium.Its architecture, operational procedures and associated software hasbeen developed at the Universities of Valencia and Birmingham on thescope to define a integrated Data Analysis System, able to perform thedaily follow-up of the instrument health, raw data files decompressionand archiving activities (on-line and historical). Pointing and telecommandfiles generation is also a SOC responsibility.The aim of this paper is to report the SOC activities during the two yearsof LEGRI operations. Conclusions about the SOC architecture and proceduresevolution on how to handle the operations for space-borne instrumentation,are also presented.Special attention has been paid to the operative evaluation of the pointingreconstruction solutions from the MINISAT-01 Attitude Control System bycomparing them with those obtained with the LEGRI Star Sensor. The analysisof one year of observations shows the good agreement between both sets ofdata. No systematic deviations have been found with an averaged standarddeviation of 1 degree in alpha and delta coordinates. For most of the timethe MINISAT pointing system is working slightly better than expected andwithin specifications.     

Origin of rapakivi granites by stochastic modeling: Vyborg and Salmi Massifs

Grain sequences of Precambrian rapakivi granites of the Vyborg and Salmi Massifs have been compared with the stochastic model for ideal granite. These sequences show that classical rapakivi granites correspond to metasomatically weakly altered granites with a simple loss of Markov transitions from quartz and plagioclase. Observed parameters of the model indirectly indicate rapakivi magma had small volatile content and large viscosity which is also characteristic of many other Precambrian granites.     

Astronomical units and constants in the general relativity framework

An attempt is made to analyze the existing system of astronomical constants within the general relativity theory (GRT) framework. The general conclusion is that, to avoid any confusion in the GRT compatible interpretation of units and constants, one should give precisely, with full post-Newtonian accuracy, the expressions of the metric forms describing the astronomical barycentric and geocentric reference systems used, for example, in IERS analysis of observations.Institute of Applied Astronomy, St. Petersburg, 197042, Russia     

A small geological data library

In a university department, small batches of geological data from different sources may be punched on cards for computer analysis. At the University of Reading efforts have been made to develop procedures for filing the cards for future reference. In a few topics, it has been possible to standardize methods of data recording. Otherwise, emphasis has been placed on documenting the data adequately. Without becoming involved in the complexities of computer storage, editing, and retrieval, a small data library has been developed in which data cards punched 5 yr ago can be found and understood today.     

Facies and allostratigraphy of high-latitude, glacially influenced marine strata of the Early Permian southern Sydney Basin, Australia

The Sydney Basin of New South Wales, Australia is a foreland basin containing a thick (up to 10 km) Permo-Triassic succession. The southern margin of the basin exposes strata deposited during Late Palaeozoic glaciation of south-eastern Gondwana. The Early Permian Wasp Head, Pebbley Beach, Snapper Point Formations and Wandrawandian Siltstone were deposited between 277 and 258 Ma on a polar, glacially influenced continental margin adjacent to ice sheets located over East Antarctica and eastern Australia. Sedimentary facies, together with related ichnofacies and fauna, can be grouped into six facies associations that record marine sub-environments ranging from high energy, storm-dominated inner shelf to turbidite-dominated upper slope settings. Cold marine conditions, with near-freezing bottom water temperatures, are recorded by glendonites. Ice-rafted debris, most likely deposited by icebergs, occurs in almost all facies associations. An allostratigraphic approach, emphasizing the recognition of bounding discontinuities (i.e. erosion surfaces and marine flooding surfaces), is used to subdivide the Early Permian stratigraphy into facies successions. Three types of succession can be identified and record changes in the relative influence of allocyclic controls such as basin tectonics, sediment supply and glacio-eustatic sea level variation. Together, sedimentological and allostratigraphic data allow reconstruction of the depositional history of the south-western margin of the Sydney Basin. Initial marine sedimentation, characterized by sediment gravity flows and storm-deposited sandstones of the lower Wasp Head Formation, occurred adjacent to a faulted basin margin. Overlying successions within the upper Wasp Head, Pebbley Beach and Snapper Point Formations, record aggradation in inner to outer shelf settings along a storm- and glacially influenced continental margin. Tectonic subsidence and basin flooding is recorded by deeper water turbidites of the Wandrawandian Siltstone.     

The greening of the McGill Paleoclimate Model. Part II: Simulation of Holocene millennial-scale natural climate changes

Various proxy data reveal that in many regions of the Northern Hemisphere (NH), the middle Holocene (6 kyr BP) was warmer than the early Holocene (8 kyr BP) as well as the later Holocene, up to the end of the pre-industrial period (1800 AD). This pattern of warming and then cooling in the NH represents the response of the climate system to changes in orbital forcing, vegetation cover and the Laurentide Ice Sheet (LIS) during the Holocene. In an attempt to better understand these changes in the climate system, the McGill Paleoclimate Model (MPM) has been coupled to the dynamic global vegetation model known as VECODE (see Part I of this two-part paper), and a number of sensitivity experiments have been performed with the green MPM. The model results illustrate the following: (1) the orbital forcing together with the vegetation—albedo feedback result in the gradual cooling of global SAT from about 6 kyr BP to the end of the pre-industrial period; (2) the disappearance of the LIS over the period 8–6 kyr BP, associated with vegetation—albedo feedback, allows the global SAT to increase and reach its maximum at around 6 kyr BP; (3) the northern limit of the boreal forest moves northward during the period 8–6.4 kyr BP due to the LIS retreat; (4) during the period 6.4–0 kyr BP, the northern limit of the boreal forest moves southward about 120 km in response to the decreasing summer insolation in the NH; and (5) the desertification of northern Africa during the period 8–2.6 kyr BP is mainly explained by the decreasing summer monsoon precipitation.     

Light propagation in a universe with spatial inhomogeneities

A light propagation in a universe which is homogeneous only in average systematically differs from a light propagation in a strictly homogeneous Universe. We demonstrate a link between this effect and the general theory of transport phenomenon in random media. The effective spatial curvature of a universe which is homogeneous only in average is introduced. This curvature is governing a light propagation in such universe. We show that the effective spatial curvature is lower than the average curvature. It implies that a universe with critical mean density looks like a space with negative curvature.