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Following the recent rejection of a formal Anthropocene series/epoch by the Subcommission on Quaternary Stratigraphy (SQS) of the International Commission on Stratigraphy (ICS), and its subsequent confirmation by the International Union of Geological Sciences (IUGS), the opportunity arises to reset the definition of the Anthropocene. The case for informally recognizing the Anthropocene to be a major planetary event of Earth system transformation offers a promising way forward, but this has been criticized by proponents of an Anthropocene series/epoch. In order to move on from the assumption that it must be a time interval, and to foster a more transdisciplinary and inclusive approach, the main points of the critique must be directly addressed. Plain Language Summary: The Anthropocene is best understood as an unfolding and intensifying event of human‐influenced Earth system change. Here we respond to criticisms of the case for the Anthropocene Event and explain why attention should be shifted away from the narrow question of date of start which has dominated debate up to now. The Anthropocene, we argue, is more than just a time interval. It is first and foremost a material happening or physical transformation which unfolds through time. Interdisciplinary research on the Anthropocene is more important than ever and must continue apace. Key Points: The Anthropocene is best studied as an ongoing event of human‐influenced planetary transformation rather than a time intervalThe Great Acceleration is an intensification of a larger unfolding Anthropocene Event that is spatially and temporally heterogeneousInterdisciplinary research on the Anthropocene is now more important than ever [ABSTRACT FROM AUTHOR]

Stream, floodplain, and wetland restorations enhance water quality and ecological function; however, soil health is prioritized infrequently in restoration planning and monitoring. Buried, historic, hydric soils—common across U.S. mid‐Atlantic valley bottoms beneath legacy sediments—are not included in most floodplain restoration designs, though they may retain favorable biogeochemical characteristics and host legacy microbial communities that could support ecosystem recovery if exhumed and preserved. To assess the efficacy of including historic hydric soils in floodplain restoration for nitrogen (N) removal, we characterized pre‐Euro‐American settlement wetland soils buried below legacy sediments and now exposed along incised streambanks across the mid‐Atlantic. We compared carbon (C) and N contents; C:N ratios; nitrate‐N and ammonium‐N concentrations; denitrification rates; functional genes for denitrification (nosZ) and nitrification (amoA for ammonia oxidizing archaea [AoA] + ammonia oxidizing bacteria [AoB]); and phospholipid fatty acid biomasses of historic wetland soils with contemporary wetland soils before and after an 1‐year incubation in a recently restored floodplain. Compared to modern wetland soils, historic hydric soils buried by legacy sediment are less nutrient‐rich, have fewer functional genes for and lower rates of denitrification, and possess significantly less microbial biomass. Following the 1‐year incubation, many of these concentrations, rates, and gene counts increased in historic soils, though not substantially. Ultimately, our results suggest that while inclusion of historic, hydric soils and their legacy microbiomes is valuable for N‐removal in floodplain restoration, the recovery of historic, hydric soils is predictably slow, and attainment of restoration goals, such as increased denitrification, may require multiple years. [ABSTRACT FROM AUTHOR]

The location of the San Andreas fault in the Shelter Cove area of northern California has been the subject of long-standing debate within the geological community. Although surface ruptures were reported near Shelter Cove in 1906, several subsequent workers questioned whether these ruptures represented true fault slip or shaking-related, gravity-driven deformation. This study, involving geologic and geomorphic mapping, historical research, and excavation across the 1906 rupture zone, concludes that the surface ruptures reported in 1906 were the result of strike-slip faulting, and that a significant Quaternary fault is located onshore near Shelter Cove. Geomorphic arguments suggest that the Holocene slip rate of this fault is greater than about 14 mm/yr, indicating that it plays an important role within the modern plate-boundary system. The onshore trace of the fault zone is well expressed as far north as Telegraph Hill; north of Telegraph Hill, its location is less well-constrained, but we propose that a splay of the fault may continue onshore northward for at least 9 km to the vicinity of Saddle Mountain.

Mass-balance interpretation of a soil chronosequence provides a means of quantifying elemental addition, removal, and transformation that occur in soils from a flight of marine terraces in northern California. Six soil profiles that range in age from several to 240,000 yr are developed in unconsolidated, sandy-marine, and eolian parent material deposited on bedrock marine platforms. Soil evolution is dominated by (1) open-system depletion of Si, Ca, Mg, K, and Na; (2) open-system enrichment of P in surface soil horizons; (3) relative immobility of Fe and Al; and (4) transformation of Fe, Si, and Al in the parent material to secondary clay minerals and sesquioxides. Net mass losses of bases and Si are generally uniform with depth and substantial - in some cases approaching 100%; however, the rate of loss of each element differs markedly, causing the ranking of each by relative abundance to shift with time. Loss of Si from the sand fraction by dissolution and particle-size diminution, from equivalent to 100% to less than 35% over 240 ky, mirrors a similar gain in the silt (from equivalent to 2% to 30%-50%) and clay (from equivalent to 0% to equivalent to 20%) size fractions. The Fe originally present in the sand fraction decreases from greater than 80% to less than 10%, whereas the amount of Fe present in the clay and crystalline oxyhydroxide fractions increases to 25% and 70%, respectively. Aluminum originally present in the sand fraction decreases from greater than 90% to less than 10% concurrently with an increase of Al in the organic sesquioxide and clay phases, to 10% and 50%, respectively, while only minor increases occur in the nonorganic sesquioxide phases.

The topographic evolution of orogens is fundamentally dictated by rates and patterns of bedrock-channel incision. Quantitative field assessments of process-based laws are needed to accurately describe landscape uplift and denudation in response to tectonics and climate. We evaluate and calibrate the shear stress (or similar unit streampower) bedrock-incision model by studying stream profiles in a tectonically active mountain range. Previous work on emergent marine terraces in the Mendocino triple junction region of northern California provides spatial and temporal control on rock-uplift rates. Digital elevation models and field data are used to quantify differences in landscape morphology associated with along-strike northwest to southeast changes in tectonic and climatic conditions. Analysis of longitudinal profiles supports the hypothesis that the study-area channels are in equilibrium with current uplift and climatic conditions, consistent with theoretical calculations of system response time based on the shear-stress model. Within uncertainty, the profile concavity ([Theta]) of the trunk streams is constant throughout the study area ([Theta] [approximately equals] 0.43), as predicted by the model. Channel steepness correlates with uplift rate. These data help constrain the two key unknown model parameters, the coefficient of erosion (K) and the exponent associated with channel gradient (n). This analysis shows that K cannot be treated as a constant throughout the study area, despite generally homogeneous substrate properties. For a reasonable range of slope-exponent values (n), best-fit values of K are positively correlated with uplift rate. This correlation has important implications for landscape-evolution models and likely reflects dynamic adjustment of K to tectonic changes, due to variations in orographic precipitation, and perhaps channel width, sediment load, and frequency of debris flows. The apparent variation in K makes a unique value of n impossible to constrain with present data. Keywords: channel geometry, digital elevation models, erosion rates, fluvial erosion, geomorphology, landscape evolution.

A response by Robert C. Walter and Dorothy J. Merritts to the letters to the editor about their article "Natural Streams and the Legacy of Water-Powered Mills" in the January 18, 2008 issue is presented.

Widespread deforestation, agriculture, and construction of milldams by European settlers greatly influenced valley-bottom stream morphology and riparian vegetation in the northeastern USA. The former broad, tussock-sedge wetlands with small, anastomosing channels were converted into today's incised, meandering streams with unstable banks that support mostly weedy, invasive vegetation. Vast accumulations of fine-grained "legacy" sediments that blanket the regional valley-bottom Piedmont landscape now are being reworked from stream banks, significantly impairing the ecological health of downstream water bodies, most notably the Chesapeake Bay. However, potential restoration is impaired by lack of direct knowledge of the pre-settlement riparian and upslope floral ecosystems. We studied the subfossil leaf flora of Denlingers Mill, an obsolete (breached) milldam site in southeastern Pennsylvania that exhibits a modern secondary forest growing atop thin soils, above bedrock outcrops immediately adjacent to a modified, incised stream channel. Presumably, an overhanging old-growth forest also existed on this substrate until the early 1700s and was responsible for depositing exceptionally preserved, minimally transported subfossil leaves into hydric soil strata, which immediately underlie post-European settlement legacy sediments. We interpret the eleven identified species of the subfossil assemblage to primarily represent a previously unknown, upland Red Oak-American Beech mixed hardwood forest. Some elements also appear to belong to a valley-margin Red Maple-Black Ash swamp forest, consistent with preliminary data from a nearby site. Thus, our results add significantly to a more complete understanding of the pre-European settlement landscape, especially of the hardwood tree flora. Compared with the modern forest, it is apparent that both lowland and upslope forests in the region have been modified significantly by historical activities. Our study underscores that generally overlooked subfossil leaves can provide important, local, temporally constrained paleoecological data, with much potential value in this case for stream and wetland restoration decisions in the mid-Atlantic region.