James B. Innes

Fire and flood management of coastal swamp enabled first rice paddy cultivation in east China

The adoption of cereal cultivation was one of the most important cultural processes in history, marking the transition from hunting and gathering by Mesolithic foragers to the food-producing economy of Neolithic farmers. In the Lower Yangtze region of China, a centre of rice domestication, the timing and system of initial rice cultivation remain unclear. Here we report detailed evidence from Kuahuqiao that reveals the precise cultural and environmental context of rice cultivation at this earliest known Neolithic site in eastern China, 7,700 calibrated years before present (cal. yr bp). Pollen, algal, fungal spore and micro-charcoal data from sediments demonstrate that these Neolithic communities selected lowland swamps for their rice cultivation and settlement, using fire to clear alder-dominated wetland scrub and prepare the site for occupation, then to maintain wet grassland vegetation of paddy type. Regular flooding by slightly brackish water was probably controlled by ‘bunding’ to maintain crop yields. The site’s exploitation ceased when it was overwhelmed by marine inundation 7,550 cal. yr bp. Our results establish that rice cultivation began in coastal wetlands of eastern China, an ecosystem vulnerable to coastal change but of high fertility and productivity, attractions maximized for about two centuries by sustained high levels of cultural management of the environment.

Tidal marsh stratigraphy, sea-level change and large earthquakes, i: a 5000 year record in washington, U.S.A.☆

Abstract Many of the estuaries of the Pacific Northwest of the U.S.A. and Canada contain stratigraphic sequences typified by alternating peat-mud couplets. Recent studies in this region interpret such couplets as the product of repeated large (magnitude S or 9) earthquakes on the Cascadia subduction zone. The resultant pattern of land-level movements is described by a model, the ‘earthquake deformation cycle’, of coseismic land subsidence followed by land uplift during interseismic strain accumulation. However, peat-mud couplets similar to those recorded in the Pacific Northwest are found on other less tectonically active temperate-latitude coasts, such as northwest Europe and the Atlantic coast of the U.S.A., where they have been interpreted as the product of non-seismic coastal processes. In this paper we apply the methods and scientific framework common to sea-level investigations in northwest Europe to a sequence of peat-mud couplets recorded in the lower Johns River, an estuary in southern Washington, to provide a test of the ‘earthquake deformation cycle’. Stratigraphic investigations of the intertidal sediments along the lower Johns River, using lithological, pollen, diatom and foraminiferal data, show evidence for eight coastal submergence events during the last 5000 years. To evaluate the ‘earthquake deformation cycle’ we assess the lateral extent of peat-mud couplets, the synchroneity of submergence, the presence of tsunami deposits accompanying submergence, and the suddenness and amount of submergence. Each submergence is shown to be accompanied by changes in coastal sedimentation broadly commensurate with those predicted by the ‘earthquake deformation cycle’, demonstrating the continued intermittent seismic activity of the Cascadia subduction zone throughout the mid and late-Holocene. Quantitative analyses of contemporary and fossil biostratigraphic data, using TWINSPAN and Detrended Correspondence Analysis, enable us to estimate the magnitude of submergence accompanying each peat-mud couplet. One event was accompanied by submergence of about 1.5 m or more, four events by intermediate submergence of about 1±0.5 m, and a further three events by submergence of

Modelling western North Sea palaeogeographies and tidal changes during the Holocene

Abstract Analysis of cores collected from Late Devensian (Weichselian) and Holocene sediments on the floor of the North Sea provides evidence of the transgression of freshwater environments during relative sea-level rise. Although many cores show truncated sequences, examples from the Dogger Bank, Well Bank and 5 km offshore of north Norfolk reveal transitional sequences and reliable indicators of past shoreline positions. Together with radiocarbon-dated sea-level index points collected from the Holocene sediments of the estuaries and coastal lowlands of eastern England these data enable the development and testing of models of the palaeogeographies of coastlines in the western North Sea and models of tidal range changes through the Holocene epoch. Geophysical models that incorporate ice-sheet reconstructions, earth rheology, eustasy, and glacio- and hydroisostasy provide predictions of sea-level relative to the present for the last 10 ka at 1-ka intervals. These predictions, added to a model of present-day bathymetry, produce palaeogeographic reconstructions for each time period. The palaeogeographic maps reveal the transgression of the North Sea continental shelf. Key stages include a western embayment off northeast England as early as 10 ka bp; the evolution of a large tidal embayment between eastern England and the Dogger Bank before 9 ka bp with connection to the English Channel prior to 8 ka bp; and Dogger Bank as an island at high tide by 7.5 ka bp and totally submerged by 6 ka bp. Analysis of core data shows that coastal and saltmarsh environments could adapt to rapid rates of sea-level rise and coastline retreat. After 6 ka bp the major changes in palaeogeography occurred inland of the present coast of eastern England. The palaeogeographic models provide the coastline positions and bathymetries for modelling tidal ranges at each 1-ka interval. A nested hierarchy of models, from the scale of the northeast Atlantic to the east coast of England, uses 26 tidal harmonics to reconstruct tidal regimes. Predictions consistently show tidal ranges smaller than present in the early Holocene, with only minor changes since 6 ka bp. Recalibration of previously available sea-level index points using the model results rather than present tidal-range parameters increases the difference between observations and predictions of relative sea-levels from the glacio-hydro-isostatic models and reinforces the need to search for better ice-sheet reconstructions.

Late Devensian and Holocene relative sea-level changes in northwestern Scotland: New data to test existing models

Abstract Pollen, diatom, lithostratigraphic and radiocarbon data from five sites in northwestern Scotland provide new data from an area previously devoid of reliable and precise information on Late Devensian and Holocene sea-level changes. The sites cover a range of palaeoenvironments, indicative of diversity in coastal evolution since deglaciation. For each site and palaeoenvironment the reference water (tide) level, indicative range, age and tendency of sea-level movement of all sea-level index points are quantified to enable correlation of the diverse coastal environments. The data record patterns of relative sea-level change and tendencies of sea-level movement from 12 ka BP to 1 ka BP. This is the longest and most comprehensive published record of relative sea-level change from the area. The information is used to test the accuracy of existing models of relative sea-level change. The results are only broadly consistent with a quantitative rebound model, and there is significant disagreement with empirical models during the Late Devensian and the early Holocene.

Mid-Holocene adaptations and later Mesolithic forest disturbance in Northern England

The Holocene period saw the gradual replacement of tundra vegetation by, first, pine—hazel woodland and then by thermophilous deciduous forest. Within these environments the Mesolithic cultures of the British Isles developed their foraging economy. In the Later Mesolithic (c 8500-5300 bp) we find that palaeoecological investigations provide evidence of disturbance of the forest vegetation, usually associated with the presence of fire. Although there is no direct evidence of human involvement in the cycle of disturbance and regeneration, it seems more probable to invoke the activity of human subsistence-related activities than natural autogenic processes. We suggest that in both uplands and lowlands, population pressure in the Later Mesolithic forced the adoption of more intensive use of game and vegetable resources, particularly deer and hazel nuts. Eventually, the adoption of cultivated cereals and probably of domestic animals can be seen as a shift in economy well within the scale of previous changes in subsistence strategy; there was no need for a change in social—ecological structures. Thus, the historic British tradition of reform rather than revolution seems to have had quite an early start.

Holocene isostasy and relative sea-level changes on the east coast of England

Abstract Analysis of sea-level data from the east coast of England identifies local-scale and regional scale factors to explain spatial and temporal variations in the altitude of Holocene sea-level index points. The isostatic effect of the glacial rebound process, including both the ice (glacio-isostatic) and water (hydro-isostatic) load contributions, explains regionalscale differences between eight areas: c. 20 m range at 8 cal. ka bp and by 4 cal. ka bp relative sea-level in Northumberland was above present, whereas in areas to the south relative sea level has been below present throughout the Holocene. Estimates for pre-industrial relative sea-level change range from 1.04 ± 0.12 mm a−1 in the Fenland to −1.30 ± 0.68 mm a−1 (i.e. sea-level fall) in north Northumberland, although this may overestimate the current rate of sea-level fall. Isostatic effects will produce similar relative differences in rates of sea-level change through the twenty-first century. The data agree closely with the patterns predicted by glacio- and hydro-isostatic models, but small systematic differences along the east coast await testing against new ice models. Local scale processes identified include differential isostatic effects within the Humber Estuary and the Fenland, tide range changes during the Holocene, and the effects of sediment consolidation. These processes help explain the variation in altitude between sea-level reconstructions derived from index points taken from basal peats and those from peats intercalated within thick sequences of Holocene sediments.

Mid-Holocene charcoal stratigraphy, fire history and palaeoecology at North Gill, North York Moors, UK

Abstract Small peat mires are a favourable medium for the preservation of charcoal records that can be correlated more precisely with past fire history as part of multi-proxy palaeoecological studies. The North York Moors upland has many suitable peat deposits with a well-researched palaeoenvironmental history that offer the potential for high-precision palaeofire studies. We have examined the charcoal and pollen stratigraphy at the North Gill site at a range of spatial and temporal resolutions for the mid Holocene period between about 7k and 4.5k radiocarbon years ago. In an individual core, three size-class charcoal records, large, small and microscopic, reflect the scale and location of local fire events, although the micro-charcoal curve contains a background regional signal of about 10% of the charcoal/pollen ratio. Most micro-charcoal is generated locally and deposited close to its source. At the site scale, spatial comparison of four cores shows a variable relationship between tree pollen and micro-charcoal concentrations, which is an index of the size and intensity of local fire phases. Individual fires cannot be distinguished. Fine-resolution sampling at the millimetre scale resolves major burning phases into discrete sub-phases that may reflect the effects of individual fires at this fine temporal scale. This multi-scale research indicates that detailed charcoal stratigraphies at varying resolutions are capable of interpretation in terms of local, regional and intermediate fire history.

Holocene relative sea-level changes and coastal vegetation history at Kentra Moss, Argyll, northwest Scotland

Abstract A late-Holocene fall in relative sea level in northwest Scotland, from ca. 1.3mm yr−1 to ca. 1.0 mm yr−1, is interpreted from lithostratigraphic, biostratigraphic, chronostratigraphic and numerical analyses of fossil tidal marsh and acidic peat bog communities elevated by isostatic uplift. Pollen, diatom and stratigraphic data from contemporary depositional environments are used to define the indicative range (±0.2 m) and reference water level (mean high water of spring tides or highest astronomical tide) of thirteen dated sea-level index points. No Holocene intertidal sediments are recorded above + 7.7 m OD and all sea-level index points are younger than ca. 4 kyr B.P. In parts of Kentra Moss, beyond the limit of Holocene intertidal clastic sedimentation, raised bog communities were established by at least 8.3 kyr B.P. These age and altitude parameters differ from those interpolated for the “Main Postglacial Shoreline”, but support a regional model in which isostatic uplift continues at present in the Kentra Moss area.

Holocene sea-level change and coastal evolution in the Humber estuary, eastern England: an assessment of rapid coastal change

New stratigraphic data collected from six sites in the Humber estuary establish a record of Holocene relative sea-level (RSL) change, and enable testing of four possible causes of rapid coastal change: sea-level rise, changes in sedimentation, storm-surge history, and human impact. Mean high water of spring tides (MHWST) in the Humber rose from c. 9 m OD at 7500 cal. yrs BP to 0 m OD by 4000 cal. yrs BP, at an average long-term rate of c. 3.9 mm yr-1. After this, the rate of rise gradually decreased to c. 1 mm yr’. Discrete episodes of rapid RSL rise are not identified although their absence may reflect limited data availability. However, we do observe two episodes of rapid coastal change in the Humber estuary. The first occurs between c. 3200 and 1900 cal. yrs BP, as marine conditions expand to their Holocene maximum and then contract. This pattern of coastal development differs from that in the East Anglian Fenlands, suggesting local processes control sedimentation at one or both of these sites. The second period of rapid change relates to a well-documented episode of increased storm surge activity in the Humber estuary and elsewhere in the UK and the North Sea region between c. 700 and 500 cal. yrs BP. Coastal development during this period varies considerably with erosion, accretion and flooding in different parts of the estuary system. Finally, we examine evidence for accelerated sediment delivery to the Humber estuary due to woodland clearance and prehistoric agriculture from 5700 cal. yrs BP onwards. Maximum sediment input is likely at c. 3200 to 1900 cal. yrs BP; a period which tentatively correlates with an episode of estuary infilling and shoreline advance.

Holocene coastal sedimentation in the Eastern English Channel: New data from the Romney Marsh region, United Kingdom

Abstract Multiproxy analysis (grain size, mineral magnetics, pollen, diatoms and radiocarbon dates) of deep (20 m+) cores collected from the Rye area of the Romney Marsh region are used to reconstruct coastal evolution between ca. 7000 and 2000 yr “conventional radiocarbon” B.P. A rapid phase of sea-level rise and tidal flat sedimentation occurred between ca. 7000 and 6000 “conventional radiocarbon” yr B.P., after which peat accumulation took place as a coastal barrier of sand and gravel extended eastward across Rye Bay and the rate of sea-level rise fell. Marine conditions returned to these areas at ca. 3000-2000 yr B.P. Erosion and landward migration of the barrier accompanied this return, heralding a change in the stability of the barrier and its ability to afford protection to back-barrier areas of the Romney Marsh region. Comparison with other sites in the central and eastern English Channel and the Thames estuary suggests that the prolonged removal of marine conditions from the study site accompanying barrier establishment reflects an ample sediment supply and the large volume of material within the barrier, which would have provided considerable scope for internal re-organisation when faced with changing coastal processes.