Deposition from mining, lumbering, and other such activities may occur in extra-frontier outposts prior to or without settlement of a region, so LS may apply to anthropogenic deposits in addition to PSA. Given the difficulties of (1) determining GW786034 cost the source of sedimentary materials, (2) the polygenetic histories of many deposits, and (3) complexities of isolating effects of climate change, thorough and precise identification of how sediment was produced should not be a sticking point as long as it is clear that the deposit is associated with processes substantially accelerated by human activities. The term has a logical potential to

describe broad classes of anthropogenic sediment in a variety of environments and it is increasingly being used that way in the literature. With regard to geomorphic forms and position on the landscape, LS deposits may progress through facies

changes from rills and gullies, to cobble- and gravel-bed streams in steep valleys, to floodplains and channel fill along large rivers, to fine-grained deposits in slack-water environments. Definitions that attempt to separate one part of a facies can falter if changes are time transgressive Selleck AT13387 or if channel morphogenesis has occurred. Different fluvial environments may dominate a site at different times during a depositional episode resulting in strata that represent multiple environments. For example, a meandering channel floodplain may be converted to a braided channel and revert back to a meandering channel all within a single period of settlement. A debris flow from a side valley may deposit coarse colluvium on top of laminated overbank silts leaving cobbles Sirolimus overlying fine-grained material in an historical section. Defining LS on the basis

of a particular phase or environment of deposition can be problematic. Some definitions of LS have emphasized the impacts on modern fluvial systems (Pennsylvania, 2006 and Niemitz et al., 2013). Although LS is often highly disruptive to environmental systems (Wohl and Rathburn, 2013) and this is very important in environmental management, substantial alterations to hydrologic, biologic, aquatic, riparian, and chemical functions should not be a defining condition for sediment to be classified as LS. These factors, together with common usage of the term, provide the basis for a definition of LS as sedimentary deposits generated episodically by human activities: “Legacy sediment: Earth materials—primarily alluvium [or colluvium]—deposited following human disturbances such as deforestation, agricultural land use, or mining. The phrase is often used to describe post-European floodplain sediment, also known as post settlement alluvium.