Time-Limit Assessment of some Holocene Transgressive and Regressive Periods in the Northern Netherlands

Die Arbeit diskutiert die Bedeutung von sechs Zeitgrenzen der gegenwärtigen Chronologie holozäner transgressiver und regressiver Perioden in den nördlichen Niederlanden. Der Schluß wird gezogen, daß (1) die Zeitgrenzen für die regressive Periode Holland III noch festgelegt werden muß; (2) die Zeitgrenze 3525 v. h. wohlbegründet ist, jedoch nicht den Beginn einer Subphase des Calais IVB, sondern den Beginn der transgressiven Periode des Dunkerque 0 markiert; (3) die Zeitgrenze 3325 v. h. ein Kunstprodukt ist; (4) die Zeitgrenze 3000 v. h. einem transgressivem Moorwachstum zuzuordnen ist, das in der ersten Hälfte des transgressiven Intervalls Dunkerque IA liegt und nicht am Beginn einer regressiven Phase, und daß (5) die Zeitgrenze 2650 v. h. wahrscheinlich eher den Beginn des transgressiven Intervalls Dunkerque IB markiert als das Ende der Periode Dunkerque IA.researc

Compaction and Other Sources of Error in Obtaining Sea-Level Data: Some Results and Consequences

Diese Arbeit beschreibt Beobachtungen und Ergebnisse zu Radiocarbon-Altersbestimmungen, die mit der Auswirkung verschiedener Fehlerquellen auf die Zeit/Tiefenposition von Datenpunkten zusammenhängen. Es wird (u. a.) gezeigt, daß die Vergleichbarkeit setzungsfreier Zeit/Tiefen-Datenpunkte von der Unterfläche von Torflagen, die das Einsetzen von Moorwachstum in verschiedenen Höhenlagen anzeigen, durch Setzung des beprobten Torfes, durch Wurzelkontamination und durch Kontamination mit älterem Material negativ beeinflußt werden kann.researc

Coupling instrumental and geological records of sea-level change : evidence from southern New England of an increase in the rate of sea-level rise in the late 19th century

Author Posting. © American Geophysical Union, 2004. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Geophysical Research Letters 31 (2004): L05203, doi:10.1029/2003GL018933.We construct a high-resolution relative sea-level record for the past 700 years by dating basal salt-marsh peat samples above a glacial erratic in an eastern Connecticut salt marsh, to test whether or not the apparent recent acceleration in the rate of sea-level rise (SLR) is coeval with climate warming. The data reveal an average SLR rate of 1.0 ± 0.2 mm/year from about 1300 to 1850 A.D. Coupling of the regional tide-gauge data (1856 to present) with this marsh-based record indicates that the nearly three-fold increase in the regional rate of SLR to modern levels likely occurred in the later half of the 19th century. Thus the timing of the observed SLR rate increase is coincident with the onset of climate warming, indicating a possible link between historic SLR increases and recent temperature increases.A Research Initiative Grant from the NOSAMS facility at WHOI funded the C-14 analysis. The Postdoctoral Scholar Program at WHOI (with funding provided by the U.S.G.S.), The John E. and Anne W. Sawyer Endowed Fund, and The J. Lamar Worzel Assistant Scientist Fund provided support to J. Donnelly

Saltmarsh archives of vegetation and land use change from Big River Marsh, SW Newfoundland, Canada

Pollen and plant macrofossils are often well-preserved in coastal sediments, providing a palaeoenvironmental record of sea-level and landscape change. In this study, we examine the pollen and plant macrofossil assemblages of a well-dated saltmarsh sediment core from southwest Newfoundland, Canada, to establish recent coastal vegetation and land use change, to increase the knowledge of anthropogenic activities in the area and develop pollen chronozones for reconstructing marsh accumulation rates and to examine the representation of plant macrofossil remains in the wetland pollen profile. Grouping the pollen record into upland and wetland assemblages allows local events related to hydrological change to be separated from landscape-scale changes. The wetland pollen and plant macrofossil records indicate a general acceleration in sea-level rise ca. ad 1700. The sedge pollen and plant macrofossil records attest to multiple phases of rhizome encroachment during inferred periods of marine regression. Two chronozones are identified from the upland pollen profile; the first associated with the settlement of St. George’s Bay ca. ad 1800, signalled by increases in Plantago lanceolata and Ambrosia pollen; the second with the permanent settlement of the Port au Port peninsula ca. ad 1850, indicated by increased P. lanceolata and Rumex pollen. Comparison of the plant macrofossil and wetland pollen profiles highlights the underrepresentation of grass pollen preserved in the saltmarsh sediments and a need for further analysis of the zonation, pollen dispersal and macrofossil representation of sedge species in saltmarshes

Reconstructing the accumulation history of a saltmarsh sediment core: which age-depth model is best?

Saltmarsh-based reconstructions of relative sea-level (RSL) change play a central role in current efforts seeking to quantify the relationship between climate and sea-level rise. The development of an accurate chronology is pivotal, since errors in age-depth relationships will propagate to the final record as alterations in both the timing and magnitude of reconstructed change. A range of age-depth modelling packages are available but differences in their theoretical basis and practical operation mean contrasting accumulation histories can be produced from the same dataset. We compare the performance of five age-depth modelling programs (Bacon, Bchron, Bpeat, Clam and OxCal) when applied to the kinds of data used in high resolution, saltmarsh-based RSL reconstructions. We investigate their relative performance by comparing modelled accumulation curves against known age-depth relationships generated from simulated stratigraphic sequences. Bpeat is particularly sensitive to non-linearities which, whilst maximising the detection of small rate changes, has the potential to generate spurious variations, particularly in the last 400 years. Bacon generally replicates the pattern and magnitude of change but with notable offsets in timing. Bchron and OxCal successfully constrain the known accumulation history within their error envelopes although the best-fit solutions tend to underestimate the magnitude of change. The best-fit solutions of Clam generally replicate the timing and magnitude of changes well, but are sensitive to the underlying shape of the calibration curve, performing poorly where plateaus in atmospheric 14C concentration exist. We employ an ensemble of age-depth models to reconstruct a 1500 year accumulation history for a saltmarsh core recovered from Connecticut, USA based on a composite chronology comprising 26 AMS radiocarbon dates, 210Pb, 137Cs radionuclides and an historical pollen chronohorizon. The resulting record reveals non-linear accumulation during the late Holocene with a marked increase in rate around AD1800. With the exception of the interval between AD1500 and AD1800, all modelsproduce accumulation curves that agree to within ~10 cm at the century-scale. The accumulation rate increase around AD1800 is associated with the transition from a radiocarbon-based to a 210Pb dominated chronology. Whilst repeat analysis excluding the 210Pb data alters the precise timing and magnitude of this acceleration, a shift to faster accumulation compared to the long-term rate is a robust feature of the record and not simply an artefact of the switch in dating methods. Simulation indicates that a rise of similar magnitude to the post-AD1800 increase (detrended increase of ~16 cm) is theoretically constrained and detectable within the radiocarbon-dated portion of the record. The absence of such a signal suggests that the recent rate of accumulation is unprecedented in the last 1500 years. Our results indicate that reliable (sub)century-scale age-depth models can be developed from saltmarsh sequences, and that the vertical uncertainties associated with them translate to RSL reconstruction errors that are typically smaller than those associated with the most precise microfossil-based estimates of palaeomarsh-surface elevation

Salt-marsh erosion associated with hurricane landfall in southern New England in the fifteenth and seventeenth centuries

Lithostratigraphic and radiocarbon data from the inland section of Pattagansett River Marsh, Connecticut, show that this sheltered part of the salt marsh underwent significant erosion twice during the past 600 yr, each time followed by rapid and complete infilling of the eroded space with tidal mud and low marsh and high marsh peat. We argue that the erosion cannot be attributed to increases in tidal prism or to lateral migration of tidal channels. The ±2σ age range (A.D. 1390–1470) for the first low marsh growth in the older regressive sequence agrees well with the age range (A.D. 1400–1440) for a hurricane deposit 60 km to the east. The younger regressive sequence is dated with the greatest probability to the period A.D. 1640–1670, i.e., shortly after the hurricanes of A.D. 1635 and 1638. Our conclusion that the most likely cause of the erosion was hurricane activity is relevant to paleostorm research and the study of marsh sensitivity to and recovery from storm erosion

Genesis of the "Lillemer Ridge", Marais de Dol, France .

Lithostratigraphic and morphological evidence shows that the "Sillon de Lillemer" is not a beach ridge or a fossil river course, but an inverted sediment body deposited from a tidal gully that penetrated a then existing, clay-covered peat area. The thickness of this peat deposit, at present between 0. 1 and 1 8 m, originally exceeded 4 m. Implications of this — ongoing — peat wastage for stratigraphie and paleoecologic work are briefly discussed.La lithostratigraphie et la morphologie montrent que le « Sillon de Lillemer » n'est pas une crête de plage ou un cours d'eau fossile inversé, mais une unité sédimentaire inversée déposée par un chenal de marée qui pénétrait alors dans une zone tourbeuse couverte de tangue. L'épaisseur initiale de ce dépôt organique, qui a disparu en grande partie, était au moins supérieure à 4 m. Les implications de cette destruction de tourbe — encore actuelle — pour les études stratigraphiques et paléoécologiques sont examinées brièvementVan De Plassche Orson, Altena Sytse, Bohncke Sjoerd, Diederiks Michel, Heijnis Henk, Wassenaar Eric. Genesis of the "Lillemer Ridge", Marais de Dol, France . In: Bulletin de l'Association française pour l'étude du quaternaire, vol. 24, n°2, 1987. pp. 69-72

Storm erosion during the past 2000 years along the north shore of Delaware Bay, USA

The recent impacts of tropical cyclones and severe storms on the U.S. Atlantic coast brought into focus the need for extended records of storm activity from different geomorphologic settings. Such reconstructions are typically developed from sites that experienced repeated overwash of sand into low-energy, depositional environments. However, salt-marsh sediment may also preserve a record of repeated erosion from tropical cyclones and storms. We describe late Holocene sediments beneath the Sea Breeze salt marsh (Delaware Bay, New Jersey) from more than 200 gouge cores positioned along seven transects. The stratigraphic record documents at least seven depositional sequences consisting of salt-marsh peat and mud couplets that represent dramatic changes in sedimentation regime. There are a number of processes that could produce these stratigraphic sequences against a background of rising relative sea level including: lateral migration of tidal creeks; tidal channel network and/or drainage ditch expansion; changes in sediment delivery rates; rapid relative sea-level change; tsunami; and formation of salt pans. The abrupt contacts between the salt-marsh peat and overlying intertidal mud suggest that erosion of the peat was followed by rapid infilling of accommodation space. Correlation of erosional surfaces across 2.5 km suggests a common mechanism and we propose that the erosion was caused by tropical cyclones and/or storms. We developed a chronology of repeated salt-marsh erosion and recovery using 137Cs, metal pollution (Pb concentration and stable isotopes), and radiocarbon data. Two recent episodes of salt-marsh erosion may correlate with historic tropical cyclones in AD 1903, and AD 1821/1788 that impacted the Atlantic coast of New Jersey, but the erosive nature of the Sea Breeze site hinders definitive correlation. Prehistoric erosional sequences correlate with overwash fans preserved in the regional sedimentary record. We estimated that it takes from several decades to almost 200 years for salt-marshes to recover from storm erosion