Vertical Stacking Statistics of Multi-facies Object-Based Models

Mathematical Geosciences - Equations describing facies proportions and amalgamation ratios are derived for randomly placed objects belonging to two or three foreground facies embedded in a...     

Spatiotemporal aspects of silica buffering in restored tidal marshes

Losses of pelagic diatom production resulting from silica limitation have not only been blamed for toxic algal blooms, but for the reduction in ability of coastal food webs to support higher trophic levels. Recent research has shown the importance of advective seepage water fluxes of dissolved silica (DSi) from freshwater marshes to pelagic waters during moments of riverine Si-limitation. In this study, we investigated the potential impact of recently installed new tidal areas along the Schelde estuary, located in former polder areas and characterized by so-called controlled reduced tidal regimes (CRT). Nine mass-balance studies were conducted in a newly constructed CRT in the freshwater Schelde estuary. During complete tidal cycles both DSi and amorphous silica (ASi) concentrations were monitored at the entrance culverts and in different habitats in the marsh. A swift DSi-delivery capacity was observed despite the shifted spatiotemporal frame of exchange processes compared to reference marshes. As silica-accumulating vegetation is not yet present, and difference with reference marshes’ deliveries is surprisingly small, we indicate diatomaceous debris and phytoliths to be the main silica source. Although further research is necessary on the driving forces of the different processes involved, restoration of former agricultural areas under CRT-regime provide the potential to buffer silica in the estuary.     

A giant three-stage submarine slide off Norway

One of the largest submarine slides known, The Storegga Slide, is located on the Norwegian continental margin. The slide is up to 450 m thick and has a total volume of about 5,600 km3. The headwall of the slide scar is 290 km long and the total run-out distance is about 800 km. The slide involved sediments of Quaternary to Early Tertiary age and occurred in three stages. Earthquakes combined with decomposition of gas hydrates are believed to be the main triggering agents for the slides. The first slide event is tentatively dated to be about 30,000 to 50,000 years B.P. and the two last major events are dated to be at 6,000 to 8,000 years B.P.     

Medieval Warming, Little Ice Age, and European impact on the environment during the last millennium in the lower Hudson Valley, New York, USA

Establishing natural climate variability becomes particularly important in large urban areas in anticipation of droughts. We present a well-dated bi-decadal record of vegetation, climate, land use, and fire frequency from a tidal marsh in the Hudson River Estuary. The classic Medieval Warm Period is evident through striking increases in charcoal and Pinus dominance from 800–1300 A.D., paralleling paleorecords southward along the Atlantic seaboard. Higher inputs of inorganic sediment during this interval suggest increased watershed erosion during drought conditions. The presence of the Little Ice Age ensues with increases in Picea and Tsuga, coupled with increasing organic percentages due to cooler, moister conditions. European impact is manifested by a decline in arboreal pollen due to land clearance, increased weedy plant cover (i.e., Ambrosia, Plantago, and Rumex), and an increase in inorganic particles to the watershed.     

Palaeolithic and Quaternary research in the Trent Valley (UK): contributions by early collectors

A brief history is presented here of the activities of the three most notable collectors of Lower and Middle Palaeolithic artefacts from Quaternary river terrace deposits in the Trent Valley, derived from archival material that has been largely ignored by previous research. Two, Mr. Fred W.G. Davey and Mr. George F. Turton, were local amateur collectors who did not publish the results of their work themselves and were reliant on collaboration with established archaeologists. The third, Mr. A. Leslie Armstrong, was an archaeologist best known for his work at Creswell Crags and Grimes Graves. Armstrong also made many Palaeolithic discoveries in the Trent Valley but published few details of his own material. Although such details of early Palaeolithic research in the Midlands and North of Britain are predominantly of historical interest only, they nonetheless provide a number of insights into the apparent lack of interest shown in areas north of the ‘Severn-Wash Line’ by collectors of Palaeolithic artefacts. Importantly, the dataset assembled by the Trent Valley Palaeolithic Project (TVPP) and summarized here is the only complete record of the known artefacts and archival material from the Trent, a proportion of which is now unavailable to the research community, having entered unknown private ownership since being studied. The second part of the paper relates this early research to current knowledge of the British Palaeolithic at its most northern fringes and to recent developments in reconstructing the Quaternary evolution of the River Trent.