Showing papers on "Driftwood published in 2002"

Island‐dominated landscapes of large floodplain rivers, a European perspective

Abstract: 1. The landscapes of large floodplain rivers are characterised by heterogeneous environments related to the interplay of flood flows, sediment transport and vegetation dynamics. 2. The large rivers of Europe, and probably most rivers throughout the forest biomes, were characterised by islands but over the period of major human interference, many have become dominated by incision and narrowing so that they are now characterised by single-thread and relatively simple channel forms. 3. Vegetation plays an active role in developing heterogeneous channel forms through (a) biotic processes such as seed dispersal, vegetative regeneration and succession and (b) abiotic effects such as increasing flow resistance inducing sedimentation, and decreasing bank erodibility. 4. In particular, accumulations of living driftwood (cf. dead driftwood accumulations and dispersed seedlings) accelerate sedimentation and island development. 5. River reaches with vegetated islands have a high habitat diversity. 6. The natural influences of flood disturbance, wood accumulation, vegetation growth, island development and tree die-off, cause island-dominated reaches to undergo cycles of island growth and decay that are related to cycles of aquatic habitat diversification and simplification.

Chronology of the last recession of the Greenland Ice Sheet

Abstract: A new deglaciation chronology for the ice-free parts of Greenland, the continental shelf and eastern Ellesmere Island (Canada) is proposed. The chronology is based on a new compilation of all published radiocarbon dates from Greenland, and includes crucial new material from southern, northeastern and northwestern Greenland. Although each date provides only a minimum age for the local deglaciation, some of the dates come from species that indicate ice-proximal glaciomarine conditions, and thus may be connected with the actual ice recession. In addition to shell dates, dates from marine algae, lake sediments, peat, terrestrial plants and driftwood also are included. Only offshore and in the far south have secure late-glacial sediments been found. Other previous reports of late-glacial sediments (older than 11.5 cal. kyr BP) from onshore parts of Greenland need to be confirmed. Most of the present ice-free parts of Greenland and Nares Strait between Greenland and Ellesmere Island were not deglaciated until the early Holocene. Copyright (C) 2002 John Wiley Sons, Ltd. (Less)

Enigmatic Late Cretaceous high palaeo-latitude lonestones in Chukotka, northeasternmost Asia

Abstract: Well-rounded cobbles were encountered within a low-energy restricted marine organic-rich deposit of latest Cretaceous age in Chukotka, NE Asia. The clasts are hydrodynamically incompatible with the inferred quiet depositional environment of the host sediment. Driftwood capable of tree-rafting, glacial striations, gastrolith clast clustering, and disrupting clast impact impressions typical of volcanic ejecta were absent, as were signs of traction currents. If indeed ice-rafting is responsible, this supports recent climate models and palaeobotanical data which favour seasonal marine ice cover of high northern latitudes over a wide span of boundary conditions.

Driftwood Use at Homol'ovi and Implications for Interpreting the Archæological Record

Abstract: Southwestern Archaeology is noted for its precise chronology based on tree-rings. Researchers often assume that archaeological building timbers arrived at their final destination solely through human transport; however, there is evidence that communities along rivers relied on driftwood for some of their wood needs. Wood use by inhabitants of several of the ancient Hopi villages of Homol'ovi, located along the Little Colorado River in northeastern Arizona, is examined using modern flood events as a model. The implications of driftwood for models of wood use in the archaeological record are explored in terms of chronology, species variability, and reconstructing flood events.