Land to Ocean Transfer of Erosion-Related Organic Carbon, Waipaoa Sedimentary System, East Coast, New Zealand

<p>Mountainous islands of the Pacific Rim (such as New Zealand) purportedly deliver up to 40% of the suspended sediment load and up to 35% of the riverine particulate organic carbon (POC) load to the world's oceans. On the east coast of New Zealand's North Island, the Waipaoa River drains a steep, 2205 km2 catchment located on the active collisional East Coast Continental Margin. It has an annual suspended sediment load of 15 Tg (15 x 1012 g), making up ~7% of New Zealand's total yield to the Pacific Ocean, and a mean annual POC discharge to the Pacific Ocean of 86.7 Gg (86.7 x 109 g). The annual loss of OC to the floodplain is ~9% of this annual POC discharge (~7.8 Gg). A range of analyses (including organic carbon content (%OC), stable carbon isotopes (Delta 13C), radiocarbon (14C), carbon to nitrogen ratios (C/N)a and carbon loadings (OC:SA)) were performed on correlative sediments from a transect of 7 cores from depositional sites located on the Waipaoa River floodplain and adjacent continental shelf and slope. Results were used to determine biogeochemical characteristics of organic carbon (OC) at a range of depositional sites during its transfer from terrestrial source to marine sink, and how large floods impact OC transfer to the marine environment. The high temporal variability in OC content (0.2 to 3.5%) and different source signatures (Delta 13C of -26.7 to -20.6% degrees) of Waipaoa River floodplain deposits prevented the establishment of a clear benchmark signature for flood deposits that may be recognisable in the marine sedimentary record. The high spatial and temporal variability of floodplain sediment OC, combined with the areal extent of floodplains within the catchment, indicates the appreciable modulating effect the floodplain has on OC transfers to the ocean. Since extensive stopbanks were constructed on the main floodplain since the 1940' s, sequestration of OC in floodplain sediments has reduced by about half, increasing the overall efficiency of the Waipaoa River in transferring terrestrial OC directly to the marine environment. Flood layers are preserved in the marine sedimentary record. Continental shelf sediments indicate that during Cyclone Bola (March 1988, a rainfall event with a >100 year return period), the extreme river discharge produced a hyperpycnal (negatively buoyant) plume, preserved as a ~10 cm thick layer on the inner shelf and a ~1 cm thick layer on the mid-shelf. The flood layer contains a significant amount of terrestrially-sourced OC (up to 86% of total OC in >25 Mu m fraction) which subsequently was rapidly buried by normal marine deposits (in which ~60% of OC in >25 Mu m fraction is terrestrial), thereby preserving its strong terrestrial source signature. As sediments are physically and biologically processed at various depositional sites across the continental shelf and slope, they lose some of their modern terrestrial OC, and the concurrent addition of marine sourced OC results in the sediments gaining a stronger marine biogeochemical signature (Delta 13C values increasing from -26.2% degrees for floodplain sediments to -21.6% degrees for upper continental slope sediments). Carbon loading (OC:SA) and 14C data revealed the contributions of kerogen, modern terrestrial OC and modern marine OC to the total OC of continental shelf and slope surface sediments. Sediments retain about 40% of their terrestrial OC following transport to the continental slope, of which a significant amount consists of kerogen. Because of high erosion rates within the catchment, kerogen associated with the particles escapes oxidation, and therefore makes up a large part of the POC flux. Kerogen is preserved across the margin to the mid-slope, where only 8% of the bulk sediment OC consists of modern terrestrial OC, 58% is modern marine OC and 34% is kerogen. Biomarker analyses of surface samples also support findings that terrestrial OC is being transferred across the continental margin, with plant sterols, long chain alcohols and long chain fatty acids (biomarkers indicative of vascular plants) persisting as far offshore as the mid-continental slope. Results presented verify and add to the understanding of OC transfers and transformations at a range of depositional sites from terrestrial source to marine sink. This study provides the first quantitative assessment of land to ocean OC transfers from New Zealand. These findings, together with information on sediment budgets and depositional rates of OC in terrestrial and marine depositional environments, could provide a vital step toward establishing global OC budgets for small mountainous island environments.</p>

Land to Ocean Transfer of Erosion-Related Organic Carbon, Waipaoa Sedimentary System, East Coast, New Zealand

<p>Mountainous islands of the Pacific Rim (such as New Zealand) purportedly deliver up to 40% of the suspended sediment load and up to 35% of the riverine particulate organic carbon (POC) load to the world's oceans. On the east coast of New Zealand's North Island, the Waipaoa River drains a steep, 2205 km2 catchment located on the active collisional East Coast Continental Margin. It has an annual suspended sediment load of 15 Tg (15 x 1012 g), making up ~7% of New Zealand's total yield to the Pacific Ocean, and a mean annual POC discharge to the Pacific Ocean of 86.7 Gg (86.7 x 109 g). The annual loss of OC to the floodplain is ~9% of this annual POC discharge (~7.8 Gg). A range of analyses (including organic carbon content (%OC), stable carbon isotopes (Delta 13C), radiocarbon (14C), carbon to nitrogen ratios (C/N)a and carbon loadings (OC:SA)) were performed on correlative sediments from a transect of 7 cores from depositional sites located on the Waipaoa River floodplain and adjacent continental shelf and slope. Results were used to determine biogeochemical characteristics of organic carbon (OC) at a range of depositional sites during its transfer from terrestrial source to marine sink, and how large floods impact OC transfer to the marine environment. The high temporal variability in OC content (0.2 to 3.5%) and different source signatures (Delta 13C of -26.7 to -20.6% degrees) of Waipaoa River floodplain deposits prevented the establishment of a clear benchmark signature for flood deposits that may be recognisable in the marine sedimentary record. The high spatial and temporal variability of floodplain sediment OC, combined with the areal extent of floodplains within the catchment, indicates the appreciable modulating effect the floodplain has on OC transfers to the ocean. Since extensive stopbanks were constructed on the main floodplain since the 1940' s, sequestration of OC in floodplain sediments has reduced by about half, increasing the overall efficiency of the Waipaoa River in transferring terrestrial OC directly to the marine environment. Flood layers are preserved in the marine sedimentary record. Continental shelf sediments indicate that during Cyclone Bola (March 1988, a rainfall event with a >100 year return period), the extreme river discharge produced a hyperpycnal (negatively buoyant) plume, preserved as a ~10 cm thick layer on the inner shelf and a ~1 cm thick layer on the mid-shelf. The flood layer contains a significant amount of terrestrially-sourced OC (up to 86% of total OC in >25 Mu m fraction) which subsequently was rapidly buried by normal marine deposits (in which ~60% of OC in >25 Mu m fraction is terrestrial), thereby preserving its strong terrestrial source signature. As sediments are physically and biologically processed at various depositional sites across the continental shelf and slope, they lose some of their modern terrestrial OC, and the concurrent addition of marine sourced OC results in the sediments gaining a stronger marine biogeochemical signature (Delta 13C values increasing from -26.2% degrees for floodplain sediments to -21.6% degrees for upper continental slope sediments). Carbon loading (OC:SA) and 14C data revealed the contributions of kerogen, modern terrestrial OC and modern marine OC to the total OC of continental shelf and slope surface sediments. Sediments retain about 40% of their terrestrial OC following transport to the continental slope, of which a significant amount consists of kerogen. Because of high erosion rates within the catchment, kerogen associated with the particles escapes oxidation, and therefore makes up a large part of the POC flux. Kerogen is preserved across the margin to the mid-slope, where only 8% of the bulk sediment OC consists of modern terrestrial OC, 58% is modern marine OC and 34% is kerogen. Biomarker analyses of surface samples also support findings that terrestrial OC is being transferred across the continental margin, with plant sterols, long chain alcohols and long chain fatty acids (biomarkers indicative of vascular plants) persisting as far offshore as the mid-continental slope. Results presented verify and add to the understanding of OC transfers and transformations at a range of depositional sites from terrestrial source to marine sink. This study provides the first quantitative assessment of land to ocean OC transfers from New Zealand. These findings, together with information on sediment budgets and depositional rates of OC in terrestrial and marine depositional environments, could provide a vital step toward establishing global OC budgets for small mountainous island environments.</p>

Age and Palynological Characteristics of Floodplain Deposits of the Kolyma Lowland (North-East Siberia)

River floodplains, reaching several kilometers in width, are one of the main landscape features of the Kolyma Lowland. Their relationship with other forms of relief - yedoma, alasses, and fragments of river terraces - is seen clearly in the Bolshaya Kuropatoch'ya River basin, which is located in the Lowland between 156°30' E and 157°15' E. The first radiocarbon dating of the floodplain deposits of the Kolyma Lowland was undertaken in a study of an outcrop on the left bank of the Bolshaya Kuropatoch'ya River (71°40' N, 156°45' E). Here floodplain sediments, represented by the alternating layers of alluvial silt and peat with a total thickness of 5 m, were exposed along a steep bank of an oxbow lake. The radiocarbon results show that the formation of the modern floodplain of the Bolshaya Kuropatoch'ya River began at the end of the Middle Holocene and continued during the Late Holocene to the present. Since the vegetation cover of arctic and subarctic regions is characterized by low pollen productivity, the spore-pollen spectra of modern and fossil plant communities often include an increased amount of pollen from plant species exotic to the Arctic, brought to the site by long-distance wind transport. For a more reliable interpretation of the spore- pollen spectra of the floodplain sediments, an analysis of the modern vegetation in the Bolshaya Kuropatoch'ya River basin and in a coastal area bordering the East Siberian Sea (about 71°05' N) was carried out, accompanied by an herbarium collection. The radiocarbon-dated palynological data indicate the development of the modern Betula-Salix shrub-herbaceous tundra during the second half of the Holocene. The establishment of this vegetation community reflects the replacement of an earlier Betula forest-tundra, which had prevailed in the northern regions of Western Beringia during the Early Holocene and included Duschekia fruticosa and large shrub species of Salix. Such dramatic changes in the vegetation cover were associated with the rise in sea level about 7.000-6.000 years ago, when seas approached modern levels. This change, in turn, led to a decrease in the contrast of summer and winter temperatures and, thus, to a decrease in the continentality of the climate and a significant reduction in the growing season in the coastal regions of the East Siberian Sea.

PETROLOGY AND PROVENANCE OF THE NATURAL STONE TOOLS FROM Al-DALMAJ ARCHAEOLOGICAL SITE, MESOPOTAMIAN PLAIN, IRAQ

Many stone tools were found on a hill south of the Hor Al-Dalmaj which is located in the central part of the alluvial plain of Mesopotamia, between the Tigris and Euphrates Rivers. The types of rocks from which the studied stone tools were made are not found in the alluvial plain, because it consists of friable sand, silt, and clay. All existing sediments were precipitated in riverine environments such as point bar, over bank, and floodplain sediments. The collected stone tools were described with a magnifying glass (10 x) and a polarized microscope after they were thin sectioned. Microscopic analysis showed that these stone tools are made of sedimentary, volcanic igneous and metamorphic rocks, such as: sandstones, limestones, chert, conglomerate, rhyolite, basalt, mica schist, and quartzite. The current studied stone tools were used by ancient humans as pestles, querns, scrapers, and knives. The present study showed that these tools were transported from outside the alluvial plain of Mesopotamia. A stone tool at the archaeological site of Al-Dalmaj indicates that there were some trade routes that connected this site with its surrounding; in addition to the economic, and that might occurred cultural exchanges during the Neolithic Period.

A novel combination of core drillings with 2D and 3D geophysical measurements helps to decipher the fluvial architecture of buried floodplain sediments of the Weiße Elster River (Central Germany)

&lt;p&gt;Fluvial sediments are valuable archives of late Quaternary landscape evolution, paleoenvironmental changes and human-environmental interactions. However, given their complex and non-linear character their correct interpretation requires a good understanding of the fluvial architecture. The fluvial architecture describes the spatial arrangement and genetic interconnectedness of different types of fluvial sediments in a floodplain such as channel and overbank deposits. To properly map the different fluvial forms, their variations in composition and geometry must be understood in three dimensions. However, whereas investigations of the fluvial architecture are relatively easy in cohesive floodplain types with incised channel beds and large natural exposures, these are challenging in floodplains with buried stratigraphies where artificial exposures or corings are required.&lt;/p&gt;&lt;p&gt;We studied three cross sections through the floodplain of the middle and upper course of the Wei&amp;#223;e Elster River in Central Germany by means of geophysical Electrical Resistivity Measurements (ERT) and closely spaced drillings. These 2D investigations were complemented by spatial geophysical 3D measurements of Electromagnetic Induction (EMI) in the surrounding areas of the cross sections. The latter technique allows fast mapping of larger areas, and was only rarely applied to fluvial systems so far. Our novel and cost-effective combination of core drillings with multidimensional geophysical measurements allowed to systematically reconstruct the fluvial architecture of larger areas of the Wei&amp;#223;e Elster floodplain with high resolution, and thereby demonstrates its high value for fluvial geomorphology. Furthermore, in combination with ongoing numerical datings of the fluvial sediments these investigations form the base for precise conclusions about possible climatic and human drivers of the Holocene fluvial dynamics of the Wei&amp;#223;e Elster River.&lt;/p&gt;

Plastics and microplastics – A future marker to reconstruct floodplain chronology (Opinion)

&lt;p&gt;After approximately two decades of plastic research in freshwater environments, plastics and especially microplastics (d&amp;#160;&lt;&amp;#160;5&amp;#160;mm) have entered the scientific consciousness as an anthropogenic pollutant. Even if this pollutant shows certain comparability with heavy metal pollution in soils and sediments, it should be seen as a purely anthropogenic material without geochemical or natural background loads, which leads to the assumption that it might also be a potential marker of the Anthropocene. Regarding the global plastic cycle within the environment, rivers act as main transport paths from land-to-sea. As rivers are embedded into landscapes, accumulation of plastics within riverine (e.g. sediment temporary sink) and accompanied terrestrial environments (e.g., floodplain storage for deposited plastics) has been proven in initial studies.&lt;/p&gt;&lt;p&gt;In contrast to other natural or anthropogenic pollutants, the approximate time since plastics and microplastic can be introduced into the environment starts in the 1950's with increasing global plastic production and consumption. A steady increase of possible plastic loads with the rising plastic production, probably decreasing with beginning environmental responsibility (approx. 2010 or beyond) leads to the fact, that plastic contents mainly occur in sediments and soils over a period of the last 70 years. This circumstance in connection with the general known sink function of soils and sediments, especially floodplains, nutrients as well as pollutants, allows the consideration of plastic deposits for dating purposes. As different dating methods reach their limits regarding comparatively young sediments, the connection between plastic deposition depth and temporal entry provides a basis for dating recent sediment layers. Possible detailed age differentiations in dependence on the identification of polymer types and additives, particle surface appearance (e.g., fresh/weathered) or spectroscopic criteria (e.g., surface weathering determination) are thinkable.&lt;/p&gt;&lt;p&gt;The opinion presented here, aims to address this new opportunity on the basis of own research findings within floodplains as well as other studies and highlights two main requirements: The first requirement for a sufficient dating implementation of plastic particles is the particle size: Detection and application for dating purposes is relatively easy to apply for macro- and mesoplastic particles (&amp;#707;5 mm), due to size and less mobility in soils or sediments (e.g., plastic films embedded in sediment structure). In contrast for particles in the microplastic size class (&amp;#706; 5mm down to 1 &amp;#181;m) we recommend only the consideration of coarse microplastics (&amp;#707; 2mm) as smaller particles could easily shift in soils and sediments (e.g., bioturbation, preferential flow).&amp;#160; Additionally, the selection of a suitable sampling site as a second requirement depends on the appropriate localization within the floodplain area and surface morphology, sampling depth, flood history and anthropogenic influences.&lt;/p&gt;&lt;p&gt;Apart from the numerous potential environmental risks of plastics, their purely anthropogenic production and their respectively features, can turn them into a useful dating tool in river and floodplain sediments and thus enabling, besides the detection alone, a further application. This approach could also be transferred to marine or lacustrine sediments in future.&lt;/p&gt;