Microalgal Communities of the Sea Ice, Ice-Covered and Ice-Free Waters of Wood Bay (Ross Sea, Antarctica) During the Austral Summer 1993 – 94

Abstract. During the austral summer 1993 – 94, microalgal density and biomass were investigated in the sea ice, in the underlying water column, in the melt water and during the formation of the sea ice. Of the 96 taxa identified, 59 were diatoms and 32 were dinoflagellates. Among the remaining five species, Pseudopleurochloris antarctica  was very abundant both in the sea ice and in the ice-free waters. Cell densities and biomass of microalgae were higher in the bottom of the sea ice and during the formation of the ice than in the seawater, and diatoms were the dominant group at higher microalgal biomass. Among these, Entomoneis kufferathii , Chaetoceros dichaeta and Fragilariopsis species were the most common taxa.     

Channel and woody debris characteristics in adjacent burned and unburned watersheds a decade after wildfire, Park County, Wyoming

Large variability in responses of stream sediment and large woody debris (LWD) to severe fire has limited the accurate prediction of the magnitude and duration of fire effects on streams. Conditions in one Absaroka Range stream that was severely burned in 1988 were compared to those in an adjacent, undisturbed stream to improve understanding of fire effects on channel and LWD characteristics beyond the first few years. Ten reaches of each stream were sampled during summer 1999.Average bankfull channel width was greater in burned Jones Creek than in unburned Crow Creek. LWD frequency and overall frequency of LWD accumulations were greater in Crow Creek than Jones Creek. Debris-jam frequency was greater in Jones Creek after accounting for differences in the frequency of pieces with length greater than channel width. Larger piece size and better anchoring contributed to more frequent, small accumulations of LWD in Crow Creek. Differences between streams in LWD frequency are consistent with greater mobility of debris in burned Jones Creek. LWD-associated fine-sediment deposits were thicker but less frequent along Jones Creek than Crow Creek.     

John Wood 2: Planning and Paying for His Town Plans

Abstract

John Wood, the 19th-century urban cartographer, surveyed almost 150 towns spread widely across Great Britain. His detailed large-scale plans are an astounding achievement. In light of this, two questions are posed: did he have a strategy that guided the places which he surveyed; and how did he pay for his work, given that so few copies of his plans appear to have been produced for sale – or at least to have survived.     

U‐series dating of the Late Pleistocene mammalian fauna from Wood Quarry (Steetley), Nottinghamshire,UK

We present the U‐series dating of bones from Wood Quarry (‘Steetley Quarry Cave’) using the diffusion–adsorption model to account for uranium uptake. The results give a weighted mean date of 66.8 ± 3.0 kyr, placing this assemblage within or just before Marine Oxygen Isotope Stage 4. The fauna is thought to correlate with the Banwell Bone Cave mammal assemblage‐zone of the Early Devensian in Britain. Our results support the idea that this assemblage‐zone immediately precedes the assemblage represented nearby at Pin Hole in Creswell Crags which is contemporary with the Mid‐Devensian and correlates with MIS 3. Our dates, and dates for the Banwell Bone Cave mammal assemblage‐zone from Stump Cross Cavern and evidence from other sites may indicate a longevity for this fauna. Copyright © 2005 John Wiley & Sons, Ltd.     

Architecture of a distal pre-vegetation braidplain: Cambrian middle member of the Wood Canyon Formation,southern Marble Mountains,California, USA

Architectural element analysis and detailed mapping of a 300 m along-strike exposure of the middle member Wood Canyon Formation, southern Marble Mountains, California, USA, provides new evidence for extensive braided–fluvial channel-belt deposits with adjacent overbank environments. Three-dimensional models constructed using ‘Structure from Motion’ techniques, combined with field-based observations, allowed interpretation of outcrop-scale trends, barforms, channel fills and fine-scale features. The ca 80 m thick member is divisible into five distinct units, including units M1 to M3 that form the bulk of the stratigraphy. Units are defined by stacking patterns of three facies associations (Facies Association 1 to Facies Association 3), each representing the product of a subenvironment within the fluvial system. In Facies Association 1, stacked cosets, interpreted as low-relief fluvial bars and channel fills, preserve vertical-accretion and downstream-accretion elements under unimodal north-north-west palaeoflow, with minor lateral accretion near bar edges. Deposits of Facies Association 2 to Facies Association 3, linked to overbank environments, are found only in unit M2, in the middle 27 m of the middle member. Floodplains, represented by Facies Association 2, include crumbly red-orange intervals of fine to medium-grained sandstone and thinner sets of cross-bedding than Facies Association 1, interbedded with thicker cross-stratification indicative of overbank splay or overland flow aggradation from adjacent channel belts during flood stage. Possible aeolian beds of Facies Association 3 preserve broad festooned trough cross-strata that average 23 cm in thickness; their small size, medium-grained sandstone and iron oxide cement suggest a high water table. The diverse assemblage of interpreted subenvironments, paired with bedform and facies patterns, implies a perennial fluvial system that gradually built large sand bars as the channel belt migrated and avulsed across an unconfined braided–fluvial reach, leaving the overbank area on its flanks subject to weathering and aeolian transport. Despite the occurrence of strata deposited in low-energy and ponded settings, and a marine influence proposed for nearby sections of middle member, no ichnofossils were encountered.     

Flume experiments on wood entrainment in rivers

A flume experiment on entrainment of woody debris is carried out. Woody debris is modeled using smooth, cylindrical dowels, in touch with the flume bed. The water depth and velocity are evaluated that initiate the motion of the partially submerged dowels. On the basis of the experimental finding, a theoretical model of log entrainment is developed, providing in dimensionless form the equilibrium equation for incipient motion. The experiment shows that the equilibrium equation must keep into account the modification of the local water profile, affecting the force balance at incipient motion. This issue has been apparently neglected in the wood entrainment models so far developed. The entrainment model is less sensitive to the choice of the apparent drag coefficient. The capability of the model in predicting the critical log diameter for initiation of motion is discussed and compared with that from the recent entrainment model from Braudrick and Grant, 2000. The comparison shows interesting results and provide evidence of the needs for further studies on wood entrainment in rivers.     

Magnetic Anomalies on the Tree Trunks

Magnetic measurements of soil and tree bark adjacent to a busy highway revealed a significant variation in the concentration of magnetic particles with distance from the highway. Further more, forest-facing tree-bark contains significantly more magnetic particles than road-facing tree-bark. Magnetic particles were detected both on the bark of the maple trees and in the first centimeter of the soil cover (O/A horizon). Stability of saturation isothermal magnetization (SIRM) and hysteresis parameters of the soil indicates the presence of single domain (SD/PSD) magnetic carriers. Measurements of the tree bark hysteresis parameters and SIRM detect a significant lower coercivity component that we interpret to be an indication of more abundant pseudo-single domain (PSD) type magnetic grains. Magnetic measurements around the perimeters of eight tree trunks reveal magnetic carriers whose distribution is antipodal to the source direction (highway). We interpret our observation by adopting an air circulation model, where suspended PSD/SD particles are carried in the air stream. The air stream from the heavy traffic lowers the amount of moisture on the tree trunk surfaces facing the highway and thus reduces an adhesive potential on this side. Therefore, more particles can stay on the moist side of the trunk protected from the direct airflow.     

Depositional features and transportation mechanism of valley-filling Iwasegawa and Kaida debris avalanches, Japan

 The depositional features of two valley-filling debris avalanche deposits were studied to reveal their transportation and depositional mechanisms. The valley-filling Iwasegawa debris avalanche deposit (ca. 0.1 km³) is distributed along the valleys at the southeastern foot of Tashirodake Volcano, northern Honshu, Japan. Debris-avalanche blocks range in size from <35 m proximally to <10 m in the distal zone and consist dominantly of fragile materials. Debris-avalanche matrix percentages increase from 35–60% in the proximal zone to 95% in the distal zone. The debris-avalanche matrix is greater in volume (80–90%) at the bottom and margins of the deposit. Normal grading of large clasts and reverse grading of wood logs and branches occur within the debris-avalanche matrix. Preferred orientation of 311 wood logs and branches within the deposit coincide with the interpreted local flow direction. The basal part of the deposit is characterized by (1) erosional features and incorporated clasts of underlying material; (2) a higher proportion (30–50%) of incorporated clasts than the upper part; and (3) reverse grading of clasts. The valley-filling Kaida debris avalanche deposit (50 000 y B.P., >0.3 km³) is distributed along the valleys at the eastern-southeastern foot of Ontake Volcano, central Japan. Debris-avalanche blocks range in size from <25 m proximally to <7 m in the medial zone. Debris-avalanche matrix percentages increase from 50–70% in the proximal zone to 80% in the distal zone. The debris-avalanche matrix is more abundant (80–90%) at the bottom part of the deposit. Deformation structures observed in the debris-avalanche blocks include elongation, folding, conjugate reverse faults, and numerous minor faults in unconsolidated materials. Lithic components within the debris-avalanche matrix tend to have a higher percentage of plucked clasts from the adjacent underlying formations. A Bingham "plug flow" model is consistent with the transportation and depositional mechanisms of the valley-filling debris avalanches. In the plug of the debris avalanche, fragile blocks were transported without major rupturing due to relatively small shear stresses in regions of small strain rate. The debris-avalanche matrix was mainly produced by shearing at the bottom and margins of the avalanche. Valley-filling debris avalanches tend to have smaller debris-avalanche blocks and larger amounts of debris-avalanche matrix than do unconfined debris avalanches. These differences may be due to disaggregation of debris-avalanche blocks by shearing against valley walls and interaction between debris-avalanche blocks and valley walls. Oriented wood logs and branches, reverse grading of clasts at the base, and a higher proportion of incorporated clasts at the base are interpreted to result from shearing along the bottom and valley walls. Received: 25 March 1998 / Accepted: 10 October 1998     

Holocene environment and subsistence patterns near the Tree Shelter, Red Sea Mountains, Egypt

The Tree Shelter site dates to the Early to Mid-Holocene (8000 to 4900 ¹⁴C yr BP). Present conditions around the site are hyperarid, but charcoal remains indicate less severe aridity at the time of its occupation. The environment around the site then supported a rich wadi vegetation, which allowed hunting during the Epipaleolithic and herding during the Neolithic occupation. Although more favorable than today, the environmental conditions also displayed a desert character and seem to have limited the range of domestic herbivores introduced in the area.