M. Bilz

Bio: M. Bilz is an academic researcher. The author has contributed to research in topics: Fossil wood & Solifluction. The author has an hindex of 1, co-authored 1 publications receiving 5 citations.

Erosion of the Geodetic Hills Fossil Forest, Axel Heiberg Island, Northwest Territories

Abstract: Studies on the erosion of the Geodetic Hills Fossil Forest on the east side of Axel Heiberg Island, Northwest Territories have indicated that erosion by wind averaged a depth of 1.3 cm for the period 1988 to 1992. The fossil wood and leaf litter tend to dry on exposure, resulting in shrinkage and fragmentation - sometimes in less than a year. Frost, especially at the boundaries of polygons, repeatedly compresses and disrupts the fossil-bearing strata. Erosion by water takes place as rills on the sides of hills. Solifluction displaces surface sediment on the sides of the hills in the range of 6 to 45 cm per year. In the last few years the physical disruption of stumps, tree trunks and forest mat has been caused mainly by people: by walking on the site, by excavating it, and by flying over and landing helicopters on it. Natural processes - including wind, freezing and thawing, rainfall, and wandering animals - also cause damage. In 1992, 62 stumps recorded in the 1988 survey (ca. 10% of the total) could not be relocated. There are problems in accounting for this discrepancy, because only a few stumps are known to have been removed by investigators for study, and it seems unlikely (although it is possible) that others may have been removed by unknown visitors. Some of the "missing" stumps may still be present, but disturbance in the surface sediment caused by scientific excavation or wind-driven accretion have made them untraceable. Vestigial stumps may simply have weathered away in the period between surveys, and finally some of the losses may be accounted for by errors in the initial surveying. Since preservation is important both for long-term scientific interpretation and for public access, the site should be better managed. The authors advocate that the site be managed by the Canadian Parks Service as an annex to Ellesmere Island National Park Reserve. Key words: fossil forest, Axel Heiberg Island, wood, leaf litter, erosion, preservation

The Arctic Forest of the Middle Eocene

Abstract: Lush forests, dominated by deciduous conifers, existed well north of the Arctic Circle during the middle Eocene (∼45 Ma). The Fossil Forest site, located on Axel Heiberg Island, Canada, has yielded a particularly rich assemblage of plant macro- and microfossils, as well as paleosols—all exquisitely preserved. Methods ranging from classical paleobotany, to stable-isotope geochemistry, have been applied to materials excavated from the Fossil Forest and have revealed layers of diverse conifer forests with a rich angiosperm understory that successfully endured three months of continuous light and three months of continuous darkness. Paleoenvironmental reconstructions suggest a warm, ice-free environment, with high growing-season-relative humidity, and high rates of soil methanogenesis. Methods to evaluate intraseasonal variability highlight the switchover from stored to actively fixed carbon during the short annual growing season.

The plant record of the dunarobba and pietrafitta sites in the plio-pleistocene palaeoenvironmental context of central italy

Abstract: Dunarobba and Pietrafitta are two outstanding fossil sites, which provide us with a glimpse on central Italian palaeoenvironments during two different time spans. The still poorly dated Dunarobba succession is framed, mainly on the basis of continental mollusc biochronology, within the Piacenzian-Gelasian interval, whereas the Pietrafitta one is reliably dated to the Calabrian thanks to vertebrate biochronology. Here we add several new palaeobotanical data for the two sites and we provide for the first time an overview of the stratigraphic, sedimentological, palaeontological and palaeoenvironmental results so-far obtained. We also review the palaeobotanical evidence concerning the neighbouring sites of Cava Toppetti I/II, Fosso Bianco, Torre Picchio and Villa San Faustino. On the basis of the available datasets we conclude that the Dunarobba Fossil Forest, with several large conifer trunks in upright position, was produced by an ancient swamp vegetation dominated by Glyptostrobus europaeus, and including few other woody (Alnus, Cephalanthus, Cornus) and herbaceous (Carex, Cladium, Schoenoplectus) plants. Rich water-transported fruit and seed assemblages and pollen data indicate that the well-drained palaeoenvironments around the Dunarobba palaeo-swamp were covered by a forest having a floristic affinity to the modern Mixed Mesophytic Forests of East Asia, as proved by the occurrence of Cryptomeria, Eurya, Sinomenium, etc. The disappearance of the Glyptostrobus swamp forest was due to the establishment of well-drained palaeoenvironmental conditions, testified by a

Geometric Evolution of Polygonal Terrain Networks in the Canadian High Arctic: Evidence of Increasing Regularity over Time

Abstract: Polygon networks are usually described qualitatively as becoming more regular through time, but such a concept has yet to be demonstrated numerically. The aim of this study is to address this question quantitatively in order to determine if polygonal terrain networks actually become more regular as they develop. Spatial point pattern analysis (SPPA), which can quantify overall network geometries based on the randomness or regularity exhibited by the spatial arrangement of polygon-bounding trough intersections, was used at three ice-wedge polygon sites in the Canadian High Arctic. SPPA was applied in two ways: (i) on the present-day networks observed in the field; and (ii) on historical arrangements derived by distinguishing primary from secondary troughs. In all cases, the polygonal networks had undergone a statistically significant regularisation over the course of their development. Although the method was applied only to terrestrial ice-wedge polygons, such an approach may also be useful for interpreting the evolution of Antarctic sublimation polygons and geometrically similar polygonal networks on Mars. Copyright © 2012 John Wiley & Sons, Ltd. and Her Majesty the Queen in Right of Canada.

New integrated data from clay lacustrine deposits of the Dunarobba Area (Umbria, Central Italy)

Abstract: This paper is aimed to illustrate and discuss new data from the clayey deposits collected in the Dunarobba area (Umbria, central Italy), and to better understand some features of the “Fosso Bianco” Unit lacustrine stage inside the South Tiberino Basin, during its latest (presumably Early Pleistocene) phases. Data come from a newly cultivated quarry area (Cava Nuova), only partly considered in previous works; the new section extends well inside the deep lake depositional stage of Fosso Bianco Unit, previously not directly described in outcrop in the Dunarobba area, but only reported from well logs. Selected samples from the Cava Nuova section were analyzed from sedimentological, geotechnical, chemical, mineralogical and biostratigraphical point of view. Sedimentological and geotechnical analyses, including density measurements, particle-size analysis, Atterberg limits and organic matter content, as well as XRF and XRPD analyses, resulted the most suitable techniques to identify the main features, at least for prevailing clayey deposits. Facies analysis and sedimentological data lead to recognize a clear depositional transition from relatively deep to shallow lacustrine deposits, which was only rarely documented formerly through a single section. On the other hand, both geotechnical and mineralogical data indicate a compositional homogeneity for clay sediments, which does not correspond with facies lateral and vertical variability nor with palaeoenvironmental complexity. Despite its preliminary nature, this integrated method looks very promising to characterize the paleodepositional context, and some hypotheses on sediment source were also evaluated. Integrated data from Cava Nuova section, as well as minor well-logs in the immediate surroundings, were discussed and compared with existing data outcoming from the whole Dunarobba area. On the heels of the recent literature, this paper is aimed to put a new light on the complexity of the Fosso Bianco paleoenvironment.

A Banded Vegetation Pattern in a High Arctic Community on Axel Heiberg Island, Nunavut, Canada

Abstract: On Axel Heiberg Island, Nunavut, Canada, a banded vegetation pattern occurred on a hillside where patterned ground and unidirectional abiotic fluxes, such as downslope water flow or wind, were not present. The parent material was the obvious source of the plant pattern, as the soils occurred on five distinct types of alluvial deposits. To examine the observed pattern, plants were inventoried and soils were sampled in July 1999. Twelve vascular species of plants, but no non-vascular species, were present at the site. Neither water, often thought to limit plant distribution in the High Arctic, nor any of the other measured soil variables, predicted plant abundance. The best predictor of plant abundance, based on regression tree analysis, was total soil nitrogen; however, higher plant density was associated with lower nitrogen. The five soil types differed in plant density and soil properties. Even though the sand soil always had soil nutrients equal to or lower than the blocky clay soil, the sand a...