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.

Impacts of vegetation and palaeohydrological changes on the n-alkane composition of a Holocene peat sequence from the Upper Vistula Valley (southern Poland)

Purpose The analysis of n-alkanes in palaeoenvironmental studies of peatlands is mainly limited to ombrogenous peatlands which are a rare feature in the environment. Using n-alkane and plant macrofossil analysis, we have tracked changes in the environment in the valley of a large Central European river. We tested the possibilities for applying such studies to low-moor bogs which are the most commonly occurring type of bog in the world. Materials and methods Representative peat samples were taken from two profiles in a peatland located in the Vistula Valley (southern Poland), and they were analysed for the occurrence and distribution of biomarkers. The distribution of n-alkanes was determined using gas chromatography-mass spectrometry (GC–MS). The botanical composition of the samples was determined by analysis of plant macrofossil remains, and the degree of peat decomposition was also determined. Results and discussion Samples of low-moor peat were characterised by a prevalence of medium- and long-chain n-alkane homologues, which is typical for higher plants. The variable values of the CPI, CPI (25–31), and the C23/C25 ratio have provided information on the stages of formation of the Zapadź bog. The source of n-alkane differentiation is vegetation change related to palaeohydrological dynamics and palaeoenvironmental conditions within the peatland. Conclusions We have shown that analysis of n-alkanes can be successfully used in low-moor bogs as a complement to palaeobotanical and palaeozoological methods. The bringing together of these types of research enables changes in the ecosystems of large river valleys to be tracked.

Peat isotopic composition of a deep deposit of palsa mire for the reconstruction of environmental changes in permafrost domain of Northern Siberia

<p>Palsa peatlands are a significant carbon pool in Northern hemisphere which is subjected to change due to accelerated permafrost thaw and peat decomposition with progressing global warming. On the other hand, peat deposits of palsas serve as an important conduit of information about variability of environment conditions in the past millennia and respective vegetation changes. In our study we applied the multi-proxy record to distinguish variation in hydrothermal regimes of palsa peatland in Northern Siberia and to trace the likely diagenetic alteration of accumulated peat.</p><p>The study site is located 10 km North-East of Igarka settlement (67<sup>o</sup>31’ N, 86<sup>o</sup>38’E) within the area underlain discontinuous permafrost. The peat core was obtained in the central intact part of elevated (ca. > 3.5 m above surrounding hollows) dry hummock. The active layer, thawed seasonally layer, at the coring site was about 0.6 m. The entire depth of peat deposit was 8.6 m, but interrupted with several relatively thin (0.1-0.2 m) ice-rich lenses. Thawed and frozen peat samples of 0.5-5.0 cm thickness (mean = 2.8 cm) were collected at 2.5-12.0 cm step (mean =5.4 cm) depending on the amount of peat material. Collected samples (n = 160) after drying at 60<sup>o</sup>C for 48 h were subjected to the analysis for C and N content, stable isotopic composition of C and N. These measurements will further accompany radiocarbon dating, loss on ignition, plant macrofossil and macro charcoal analyses.</p><p>The analyzed 8.6 m deep peat core demonstrated the large variation of C (17.3-54.7%) and N (0.37-3.26 %) contents as well as C:N ratios (14-134). The isotopic depth profile was in the range from -24.51 to -34.31 ‰ for d<sup>13</sup>C and from -1.77 to 6.96 ‰ for d<sup>15</sup>N. The highest enrichment in <sup>15</sup>N (2.69±1.60 ‰ d<sup>15</sup>N) was found in seasonally thawed layer (≤0.6 m). A layer close to the bottom (6.9-8.3 m) contained peat the most depleted by <sup>13</sup>C (<-30 ‰ d<sup>13</sup>C). Meanwhile, along the peat profile depth we detected significant fluctuations in these parameters suggesting the different periods with specific environmental conditions.</p><p>Further combined with radiocarbon dating and plant macrofossil analyses we will attempt to capture the changes occurred during the past epochs in an input matter (vegetation changes and/or its productivity), decomposition rates as well as hydrothermal regimes and permafrost processes like aggradation (e.g. hummock uplift and cryoturbation) and degradation (e.g. hummock collapse, shifts from minerotrophic to ombrotrohic conditions and vice versa).</p><p>This work was supported by the Russian Science Foundation, project № 20-17-00043.</p>

Røysundersøkelser i Løten, Hedmark

In 2015, the Museum of Cultural History organized a large excavation project in Løten, Hedmark with over 90 sites. During the project both clearance cairns and cairns interpreted as graves were excavated. The field at Skillingstad contained more than 100 cairns, of which approximately 40 were excavated. Although originally thought to be clearance cairns, results obtained over the course of the excavation demanded that this interpretation be reconsidered. In the area surrounding Skillingstad, four smaller cairn fields were also excavated, ranging in size from 4 to 21 cairns. Several of these were associated with small, oval, bowl-shaped fields that overlapped in time with the graves at Skillingstad. The plant macrofossil analyses returned few interesting results, but the cairns containing graves and the clearance cairns differed significantly in their micromorphological results. In addition, there were clear differences in structural organization and the relationship between the cairns in the grave and clearance fields respectively. The burial cairns were spread evenly across the site, built with uniform sized rocks and placed with respect to older monuments such that none of the monuments merged into larger units. In contrast, the clearance cairns were more randomly distributed across the site, sometimes cleared to one side of the field and at other sites in between the cultivated land and pastures. The rocks in these cairns were also more variable in size and often several cairns had grown together over time. We will also share some administrative experiences based on the reinterpretation from clearance cairns to graves at Skillingstad.