<p>The most important river of the European Union, the Danube, large sediment and n... more <p>The most important river of the European Union, the Danube, large sediment and nutrient influxes in the last millennium ultimately led to drastic morphological and ecological changes at the oceanic end of this system, the Black Sea. We suggested that these transformations are the result of the Ottoman Empire expansion into the Balkans between 1350 and 1450 A.D. Adoption of the Islamic cultural package in the region may have led to rapid deforestation of highlands for sheep farming at the expense of traditional small-scale cattle and pig farming. Alternative theories to explain this cascade of system-scale sedimentary changes are either agricultural - (a) the adoption of corn as the main staple from the Columbian exchange after 1500 AD, or climatic - (b) climate cooling during the Little Ice Age (LIA) after 1400 AD. In the case of Danube, such interdependencies between Nature and Culture are many. Searching for historical lessons, we review them starting from <em>Homo sapiens’</em> and Neolithic agriculture expansions into Europe, ancient Greek and Roman engineering interventions long the river, the <em>avant-la-lettre</em> ecological management of the lower floodplain under Grigore Antipa, the catastrophic communist abuse of the combined natural-human system and explore their expression in the sedimentary architecture of the floodplain.</p>
Fluvial export of organic carbon (OC) and burial in ocean sediments comprises an important carbon... more Fluvial export of organic carbon (OC) and burial in ocean sediments comprises an important carbon sink, but fluxes remain poorly constrained, particularly for specific organic components. Here OC and lipid biomarker contents and isotopic characteristics of suspended matter determined in depth profiles across an active channel close to the terminus of the Danube River are used to constrain instantaneous OC and biomarker fluxes and integrated compositions during high to moderate discharges. During high (moderate) discharge, the total Danube exports 8 (7) kg/s OC, 7 (3) g/s higher plant-derived long-chain fatty acids (LCFA), 34 (21) g/s short-chain fatty acids (SCFA), and 0.5 (0.2) g/s soil bacterial membrane lipids (brGDGTs). Integrated stable carbon isotopic compositions were TOC:
Abundances and distributional changes of branched glycerol dialkyl glycerol tetraethers (brGDGTs)... more Abundances and distributional changes of branched glycerol dialkyl glycerol tetraethers (brGDGTs) in fluvially influenced sediments are used in various paleoclimate studies to reconstruct variations in soil export, continental air temperature and soil pH in corresponding river basins. For accurate interpretation of these records, it is important to understand the provenance and the evolution of biomarker signals as they move through the river system. Here we investigate the brGDGT composition of modern river sediments of the Danube River, the second largest river in Europe. BrGDGT-based mean annual air temperature and soil pH parallel the actual values of air temperature and soil pH from the upper to the lower basin, showing that signals predominantly reflect local as opposed to basin-wide environmental conditions. Furthermore, data generated using the recently developed method with improved chromatography, separating the 6-methyl-isomers from the 5-methyl-isomers, was compared with that resulting from the conventional method. We show that the temperatures and pH values reconstructed using the data obtained by improved chromatography best resemble the local environmental conditions throughout the Danube River basin. Our results highlight the importance of in-depth studies within river systems to better understand the provenance of biomarker signals in fluvially derived sedimentary archives.
EarthArXiv (California Digital Library), Dec 18, 2022
Records of paleofloods can be reconstructed from special fluvial sedimentary environments such as... more Records of paleofloods can be reconstructed from special fluvial sedimentary environments such as oxbows; however, deposits in in such lakes, if they exist at all, are still short, on the order of hundreds of years. Longer sedimentary records need to be developed for evaluating paleo-hydrologic regimes of large rivers transiting from a natural Holocene to Anthropocene. Here we report core logs, radiocarbon dates and electrical resistivity tomography data from the Danube lower region and delta collected toward evaluating their potential for paleohydrological reconstructions.
Abundances and distributional changes of branched glycerol dialkyl glycerol tetraethers (brGDGTs)... more Abundances and distributional changes of branched glycerol dialkyl glycerol tetraethers (brGDGTs) in fluvially influenced sediments are used in various paleoclimate studies to reconstruct variations in soil export, continental air temperature and soil pH in corresponding river basins. For accurate interpretation of these records, it is important to understand the provenance and the evolution of biomarker signals as they move through the river system. Here we investigate the brGDGT composition of modern river sediments of the Danube River, the second largest river in Europe. BrGDGT-based mean annual air temperature and soil pH parallel the actual values of air temperature and soil pH from the upper to the lower basin, showing that signals predominantly reflect local as opposed to basin-wide environmental conditions. Furthermore, data generated using the recently developed method with improved chromatography, separating the 6-methyl-isomers from the 5-methyl-isomers, was compared with that resulting from the conventional method. We show that the temperatures and pH values reconstructed using the data obtained by improved chromatography best resemble the local environmental conditions throughout the Danube River basin. Our results highlight the importance of in-depth studies within river systems to better understand the provenance of biomarker signals in fluvially derived sedimentary archives.
<p>The most important river of the European Union, the Danube, large sediment and n... more <p>The most important river of the European Union, the Danube, large sediment and nutrient influxes in the last millennium ultimately led to drastic morphological and ecological changes at the oceanic end of this system, the Black Sea. We suggested that these transformations are the result of the Ottoman Empire expansion into the Balkans between 1350 and 1450 A.D. Adoption of the Islamic cultural package in the region may have led to rapid deforestation of highlands for sheep farming at the expense of traditional small-scale cattle and pig farming. Alternative theories to explain this cascade of system-scale sedimentary changes are either agricultural - (a) the adoption of corn as the main staple from the Columbian exchange after 1500 AD, or climatic - (b) climate cooling during the Little Ice Age (LIA) after 1400 AD. In the case of Danube, such interdependencies between Nature and Culture are many. Searching for historical lessons, we review them starting from <em>Homo sapiens’</em> and Neolithic agriculture expansions into Europe, ancient Greek and Roman engineering interventions long the river, the <em>avant-la-lettre</em> ecological management of the lower floodplain under Grigore Antipa, the catastrophic communist abuse of the combined natural-human system and explore their expression in the sedimentary architecture of the floodplain.</p>
The Okavango rift zone/delta and the Makgadikgadi paleo-megalake form a dynamic system in norther... more The Okavango rift zone/delta and the Makgadikgadi paleo-megalake form a dynamic system in northern Kalahari, where tectonic activity, climate change, sedimentation, and biota have interacted in a complex pattern. Previous research suggested that the region may have been a hotspot for hominid evolution.Here we present results from the first scientific deep drilling project (OKAMAK) in the northern Kalahari, Botswana. Two drill cores, OKA (230 meters) and MAK (210 m), were drilled in the Okavango delta and Makgadikgadi paleolake. Cores recovered shallow and deep-water sands, muds and evaporitic lithologies of the Cenozoic Kalahari Group extending across the unconformity into the Cretaceous/Jurassic Karoo Group sandstones.We discuss initial stratigraphy, chronologies and paleoenvironmental information for this novel sedimentary record, present hypotheses to be tested on the complex climate of the region, history of river piracy, evolution of the delta and infilling phases of Makgadikga...
Records of paleofloods can be reconstructed from special fluvial sedimentary environments such as... more Records of paleofloods can be reconstructed from special fluvial sedimentary environments such as oxbows; however, deposits in in such lakes, if they exist at all, are still short, on the order of hundreds of years. Longer sedimentary records need to be developed for evaluating paleo-hydrologic regimes of large rivers transiting from a natural Holocene to Anthropocene. Here we report core logs, radiocarbon dates and electrical resistivity tomography data from the Danube lower region and delta collected toward evaluating their potential for paleohydrological reconstructions.
We performed a detrital zircon (DZ) U‐Pb geochronologic survey of the lower parts of the Danube R... more We performed a detrital zircon (DZ) U‐Pb geochronologic survey of the lower parts of the Danube River approaching its Danube delta, Black Sea sink, and a few large tributaries (Tisza, Jiu, Olt, and Siret) originating in the nearby Carpathian Mountains. Samples are modern sediments. DZ age spectra reflect the geology and specifically the crustal age formation of the source area, which in this case is primarily the Romanian Carpathians and their foreland with contributions from the Balkan Mountains to the south of Danube and the East European Craton. The zircon cargo of these rivers suggests a source area that formed during the latest Proterozoic and mostly into the Cambrian and Ordovician as island arcs and back‐arc basins in a Peri‐Gondwanan subduction setting (~600–440 Ma). The Inner Carpathian units are dominated by a U‐Pb DZ peak in the Ordovician (460–470 Ma) and little inheritance from the nearby continental masses, whereas the Outer Carpathian units and the foreland have two m...
Fluvial export of organic carbon (OC) and burial in ocean sediments comprises an important carbon... more Fluvial export of organic carbon (OC) and burial in ocean sediments comprises an important carbon sink, but fluxes remain poorly constrained, particularly for specific organic components. Here OC and lipid biomarker contents and isotopic characteristics of suspended matter determined in depth profiles across an active channel close to the terminus of the Danube River are used to constrain instantaneous OC and biomarker fluxes and integrated compositions during high to moderate discharges. During high (moderate) discharge, the total Danube exports 8 (7) kg/s OC, 7 (3) g/s higher plant‐derived long‐chain fatty acids (LCFA), 34 (21) g/s short‐chain fatty acids (SCFA), and 0.5 (0.2) g/s soil bacterial membrane lipids (brGDGTs). Integrated stable carbon isotopic compositions were TOC: −28.0 (−27.6)‰, LCFA: −33.5 (−32.8)‰ and Δ14C TOC: −129 (−38)‰, LCFA: −134 (−143)‰, respectively. Such estimates will aid in establishing quantitative links between production, export, and burial of OC from...
The Ayeyawady delta is the last Asian megadelta whose evolution has remained essentially unexplor... more The Ayeyawady delta is the last Asian megadelta whose evolution has remained essentially unexplored so far. Unlike most other deltas across the world, the Ayeyawady has not yet been affected by dam construction providing a unique view on largely natural deltaic processes benefiting from abundant sediment loads affected by tectonics and monsoon hydroclimate. To alleviate the information gap and provide a baseline for future work, here we provide a first model for the Holocene development of this megadelta based on radiocarbon and optically stimulated luminescence-dated trench and drill core sediments collected in 2016 and 2017, together with a re-evaluation of published maps, charts and scientific literature. Altogether, this data indicates that Ayeyawady is a mud-dominated delta with tidal and wave influences that has been constructed within a vertically stable Pleistocene incised valley. The sediment-rich Ayeyawady River built meander belt alluvial ridges with avulsive characters. ...
Understanding the transport history and fate of organic carbon (OC) within river systems is cruci... more Understanding the transport history and fate of organic carbon (OC) within river systems is crucial in order to constrain the dynamics and significance of land-ocean interactions as a component of the global carbon cycle. Fluvial export and burial of terrestrial OC in marine sediments influences atmospheric CO 2 over a range of timescales, while river-dominated sedimentary sequences can provide valuable archives of paleoenvironmental information. While there is abundant evidence that the association of organic matter (OM) with minerals exerts an important influence on its stability as well as hydrodynamic behavior in aquatic systems, there is a paucity of information on where such associations form and how they evolve during fluvial transport. Here, we track total organic carbon (TOC) and terrestrial biomarker concentrations (plant wax-derived long-chain fatty acids (FA), branched glycerol dialkyl glycerol tetraethers (brGDGTs) and lignin-derived phenols) in sediments collected along the entire course of the Danube River system in the context of sedimentological parameters. Mineral-specific surface area-normalized biomarker and TOC concentrations show a systematic decrease from the upper to the lower Danube basin. Changes in OM loading of the available mineral phase correspond to a net decrease of 70-80% of different biomolecular components. Ranges for biomarker loadings on Danube River sediments, corresponding to 0.4-1.5 lg FA /m 2 for long-chain (n-C 24-32 ) fatty acids and 17-71 ng brGDGT /m 2 for brGDGTs, are proposed as a benchmark for comparison with other systems. We propose that normalizing TOC as well as biomarker concentrations to mineral surface area provides valuable quantitative constraints on OM dynamics and organo-mineral interactions during fluvial transport from terrigenous source to oceanic sink.
Abundances and distributional changes of branched glycerol dialkyl glycerol tetraethers (brGDGTs)... more Abundances and distributional changes of branched glycerol dialkyl glycerol tetraethers (brGDGTs) in fluvially influenced sediments are used in various paleoclimate studies to reconstruct variations in soil export, continental air temperature and soil pH in corresponding river basins. For accurate interpretation of these records, it is important to understand the provenance and the evolution of biomarker signals as they move through the river system. Here we investigate the brGDGT composition of modern river sediments of the Danube River, the second largest river in Europe. BrGDGT-based mean annual air temperature and soil pH parallel the actual values of air temperature and soil pH from the upper to the lower basin, showing that signals predominantly reflect local as opposed to basin-wide environmental conditions. Furthermore, data generated using the recently developed method with improved chromatography, separating the 6-methyl-isomers from the 5-methyl-isomers, was compared with that resulting from the conventional method. We show that the temperatures and pH values reconstructed using the data obtained by improved chromatography best resemble the local environmental conditions throughout the Danube River basin. Our results highlight the importance of in-depth studies within river systems to better understand the provenance of biomarker signals in fluvially derived sedimentary archives.
Watershed deforestation over the last two millennia led to the rapid expansion and morphological ... more Watershed deforestation over the last two millennia led to the rapid expansion and morphological diversification of the Danube delta (Fig. ) coupled with a complete transformation of the ecosystem in the receiving marine basin, the Black Sea . During this period the central wave-dominated lobe of Sulina was slowly abandoned and the southernmost arm of the Danube, the St. George, was reactivated and started to build its second wave-dominated delta lobe at the open coast. Simultaneously, secondary distributaries branching off from the St. George branch built the Dunavatz bayhead lobe into the southern Razelm lagoon (Fig. ). This intense deltaic activity accompanied drastic changes in Danube's flow regime. Many small deltas had grown during intervals of enhanced anthropogenic pressure in their watersheds . However, finding specific causes, whether natural or anthropogenic, for such a sweeping reorganization of a major delta built by a continental-scale river like Danube requires detailed reconstructions of its depositional history. Here we provide a first look at the Danube's deltaic reorganization along its main distributary, the Chilia, and discuss potential links to hydroclimate, population growth and cultural changes in the watershed. For this reconstruction, we used sediment core-based depositional histories together with a morphological analysis of historical cartographic material and recent satellite photography (see complete methods in Supplementary data). The Chilia arm, which flows along the northern rim of Danube delta (Fig. ), has successively built three lobes and it was first mapped in detail at the end of the 18th century (Fig. ). The depositional architecture of these lobes was controlled by the entrenched drainage pattern formed during the last lowstand in the Black Sea, by the pre-Holocene loess relief developed within and adjacent to this lowstand drainage and by the development of Danube's own deltaic deposits that are older than Chilia's Carozza et al., 2012a). The oldest Chilia lobe (Fig. and) filled the Pardina Anthropocene xxx (2014) xxx-xxx
River deltas are constructed with surplus fluvial sediment that is not washed away by waves and c... more River deltas are constructed with surplus fluvial sediment that is not washed away by waves and currents or drowned by the sea. The waterlogged, low gradient deltaic landscapes favor development of marshes and mangroves, which in turn, contribute organic materials to the delta. In natural conditions, deltas are dynamic systems that adapt to changes in boundary conditions by advancing, retreating, switching, aggrading, and/or drowning. However, most modern deltas are constrained in place by societal needs such as protecting residents, resources, and infrastructure or preserving biodiversity and ecosystem services. Human activities over the last century have inadvertently led to conditions that are unfavorable for deltas . New sediment input has been severely curtailed by trapping behind river dams. Distribution of the remaining sediment load across deltas or along their shores has been altered by engineering works. And accelerating eustatic sea level rise combined with anthropogenic subsidence favors marine flooding that surpasses the normal rate of sediment accumulation, leading in time to permanent drowning of extensive regions of the delta plains. Restoration is envisioned for extensively altered deltas (e.g., , but in these hostile conditions virtually all deltas are becoming unstable and require strategies for maintenance. Availability of sediments is the first order concern for delta maintenance. Sediment budgets are, however, poorly constrained for most deltas (Blum and Roberts, 2009 and references therein). We know that fluvial sediments feed the delta plain (topset) and the nearshore delta front zone (foreset) contributing to aggradation and progradation respectively, but only limited quantitative information exists on the laws governing this sediment partition (Paola et al., 2011 and references therein). Except for deltas built in protective embayments (e.g., , the trapping efficiency appears remarkably small as over 50% of the total load may escape to the shelf and beyond . Therefore, a key strategy for delta maintenance is a deliberate and rational sediment management that would Anthropocene 1 (2013) 35-45
A catastrophic flooding of the Black Sea basin was proposed to have occurred during its reconnect... more A catastrophic flooding of the Black Sea basin was proposed to have occurred during its reconnection to the ocean in the early Holocene. Possible cultural consequences of the flood include the migration of Neolithic farmers from around the Black Sea towards central Europe as well as the creation of flood myths. Stratigraphic and paleo-geomorphologic information from Danube delta aided by radiocarbon ages on articulated mollusks constrain the level in the Black Sea before the marine reconnection to ca 30 m below the present sea level rather than 80 m or lower. If the flood occurred at all, the sea level increase and the flooded area during the reconnection were significantly smaller than previously proposed.
<p>The most important river of the European Union, the Danube, large sediment and n... more <p>The most important river of the European Union, the Danube, large sediment and nutrient influxes in the last millennium ultimately led to drastic morphological and ecological changes at the oceanic end of this system, the Black Sea. We suggested that these transformations are the result of the Ottoman Empire expansion into the Balkans between 1350 and 1450 A.D. Adoption of the Islamic cultural package in the region may have led to rapid deforestation of highlands for sheep farming at the expense of traditional small-scale cattle and pig farming. Alternative theories to explain this cascade of system-scale sedimentary changes are either agricultural - (a) the adoption of corn as the main staple from the Columbian exchange after 1500 AD, or climatic - (b) climate cooling during the Little Ice Age (LIA) after 1400 AD. In the case of Danube, such interdependencies between Nature and Culture are many. Searching for historical lessons, we review them starting from <em>Homo sapiens’</em> and Neolithic agriculture expansions into Europe, ancient Greek and Roman engineering interventions long the river, the <em>avant-la-lettre</em> ecological management of the lower floodplain under Grigore Antipa, the catastrophic communist abuse of the combined natural-human system and explore their expression in the sedimentary architecture of the floodplain.</p>
Fluvial export of organic carbon (OC) and burial in ocean sediments comprises an important carbon... more Fluvial export of organic carbon (OC) and burial in ocean sediments comprises an important carbon sink, but fluxes remain poorly constrained, particularly for specific organic components. Here OC and lipid biomarker contents and isotopic characteristics of suspended matter determined in depth profiles across an active channel close to the terminus of the Danube River are used to constrain instantaneous OC and biomarker fluxes and integrated compositions during high to moderate discharges. During high (moderate) discharge, the total Danube exports 8 (7) kg/s OC, 7 (3) g/s higher plant-derived long-chain fatty acids (LCFA), 34 (21) g/s short-chain fatty acids (SCFA), and 0.5 (0.2) g/s soil bacterial membrane lipids (brGDGTs). Integrated stable carbon isotopic compositions were TOC:
Abundances and distributional changes of branched glycerol dialkyl glycerol tetraethers (brGDGTs)... more Abundances and distributional changes of branched glycerol dialkyl glycerol tetraethers (brGDGTs) in fluvially influenced sediments are used in various paleoclimate studies to reconstruct variations in soil export, continental air temperature and soil pH in corresponding river basins. For accurate interpretation of these records, it is important to understand the provenance and the evolution of biomarker signals as they move through the river system. Here we investigate the brGDGT composition of modern river sediments of the Danube River, the second largest river in Europe. BrGDGT-based mean annual air temperature and soil pH parallel the actual values of air temperature and soil pH from the upper to the lower basin, showing that signals predominantly reflect local as opposed to basin-wide environmental conditions. Furthermore, data generated using the recently developed method with improved chromatography, separating the 6-methyl-isomers from the 5-methyl-isomers, was compared with that resulting from the conventional method. We show that the temperatures and pH values reconstructed using the data obtained by improved chromatography best resemble the local environmental conditions throughout the Danube River basin. Our results highlight the importance of in-depth studies within river systems to better understand the provenance of biomarker signals in fluvially derived sedimentary archives.
EarthArXiv (California Digital Library), Dec 18, 2022
Records of paleofloods can be reconstructed from special fluvial sedimentary environments such as... more Records of paleofloods can be reconstructed from special fluvial sedimentary environments such as oxbows; however, deposits in in such lakes, if they exist at all, are still short, on the order of hundreds of years. Longer sedimentary records need to be developed for evaluating paleo-hydrologic regimes of large rivers transiting from a natural Holocene to Anthropocene. Here we report core logs, radiocarbon dates and electrical resistivity tomography data from the Danube lower region and delta collected toward evaluating their potential for paleohydrological reconstructions.
Abundances and distributional changes of branched glycerol dialkyl glycerol tetraethers (brGDGTs)... more Abundances and distributional changes of branched glycerol dialkyl glycerol tetraethers (brGDGTs) in fluvially influenced sediments are used in various paleoclimate studies to reconstruct variations in soil export, continental air temperature and soil pH in corresponding river basins. For accurate interpretation of these records, it is important to understand the provenance and the evolution of biomarker signals as they move through the river system. Here we investigate the brGDGT composition of modern river sediments of the Danube River, the second largest river in Europe. BrGDGT-based mean annual air temperature and soil pH parallel the actual values of air temperature and soil pH from the upper to the lower basin, showing that signals predominantly reflect local as opposed to basin-wide environmental conditions. Furthermore, data generated using the recently developed method with improved chromatography, separating the 6-methyl-isomers from the 5-methyl-isomers, was compared with that resulting from the conventional method. We show that the temperatures and pH values reconstructed using the data obtained by improved chromatography best resemble the local environmental conditions throughout the Danube River basin. Our results highlight the importance of in-depth studies within river systems to better understand the provenance of biomarker signals in fluvially derived sedimentary archives.
<p>The most important river of the European Union, the Danube, large sediment and n... more <p>The most important river of the European Union, the Danube, large sediment and nutrient influxes in the last millennium ultimately led to drastic morphological and ecological changes at the oceanic end of this system, the Black Sea. We suggested that these transformations are the result of the Ottoman Empire expansion into the Balkans between 1350 and 1450 A.D. Adoption of the Islamic cultural package in the region may have led to rapid deforestation of highlands for sheep farming at the expense of traditional small-scale cattle and pig farming. Alternative theories to explain this cascade of system-scale sedimentary changes are either agricultural - (a) the adoption of corn as the main staple from the Columbian exchange after 1500 AD, or climatic - (b) climate cooling during the Little Ice Age (LIA) after 1400 AD. In the case of Danube, such interdependencies between Nature and Culture are many. Searching for historical lessons, we review them starting from <em>Homo sapiens’</em> and Neolithic agriculture expansions into Europe, ancient Greek and Roman engineering interventions long the river, the <em>avant-la-lettre</em> ecological management of the lower floodplain under Grigore Antipa, the catastrophic communist abuse of the combined natural-human system and explore their expression in the sedimentary architecture of the floodplain.</p>
The Okavango rift zone/delta and the Makgadikgadi paleo-megalake form a dynamic system in norther... more The Okavango rift zone/delta and the Makgadikgadi paleo-megalake form a dynamic system in northern Kalahari, where tectonic activity, climate change, sedimentation, and biota have interacted in a complex pattern. Previous research suggested that the region may have been a hotspot for hominid evolution.Here we present results from the first scientific deep drilling project (OKAMAK) in the northern Kalahari, Botswana. Two drill cores, OKA (230 meters) and MAK (210 m), were drilled in the Okavango delta and Makgadikgadi paleolake. Cores recovered shallow and deep-water sands, muds and evaporitic lithologies of the Cenozoic Kalahari Group extending across the unconformity into the Cretaceous/Jurassic Karoo Group sandstones.We discuss initial stratigraphy, chronologies and paleoenvironmental information for this novel sedimentary record, present hypotheses to be tested on the complex climate of the region, history of river piracy, evolution of the delta and infilling phases of Makgadikga...
Records of paleofloods can be reconstructed from special fluvial sedimentary environments such as... more Records of paleofloods can be reconstructed from special fluvial sedimentary environments such as oxbows; however, deposits in in such lakes, if they exist at all, are still short, on the order of hundreds of years. Longer sedimentary records need to be developed for evaluating paleo-hydrologic regimes of large rivers transiting from a natural Holocene to Anthropocene. Here we report core logs, radiocarbon dates and electrical resistivity tomography data from the Danube lower region and delta collected toward evaluating their potential for paleohydrological reconstructions.
We performed a detrital zircon (DZ) U‐Pb geochronologic survey of the lower parts of the Danube R... more We performed a detrital zircon (DZ) U‐Pb geochronologic survey of the lower parts of the Danube River approaching its Danube delta, Black Sea sink, and a few large tributaries (Tisza, Jiu, Olt, and Siret) originating in the nearby Carpathian Mountains. Samples are modern sediments. DZ age spectra reflect the geology and specifically the crustal age formation of the source area, which in this case is primarily the Romanian Carpathians and their foreland with contributions from the Balkan Mountains to the south of Danube and the East European Craton. The zircon cargo of these rivers suggests a source area that formed during the latest Proterozoic and mostly into the Cambrian and Ordovician as island arcs and back‐arc basins in a Peri‐Gondwanan subduction setting (~600–440 Ma). The Inner Carpathian units are dominated by a U‐Pb DZ peak in the Ordovician (460–470 Ma) and little inheritance from the nearby continental masses, whereas the Outer Carpathian units and the foreland have two m...
Fluvial export of organic carbon (OC) and burial in ocean sediments comprises an important carbon... more Fluvial export of organic carbon (OC) and burial in ocean sediments comprises an important carbon sink, but fluxes remain poorly constrained, particularly for specific organic components. Here OC and lipid biomarker contents and isotopic characteristics of suspended matter determined in depth profiles across an active channel close to the terminus of the Danube River are used to constrain instantaneous OC and biomarker fluxes and integrated compositions during high to moderate discharges. During high (moderate) discharge, the total Danube exports 8 (7) kg/s OC, 7 (3) g/s higher plant‐derived long‐chain fatty acids (LCFA), 34 (21) g/s short‐chain fatty acids (SCFA), and 0.5 (0.2) g/s soil bacterial membrane lipids (brGDGTs). Integrated stable carbon isotopic compositions were TOC: −28.0 (−27.6)‰, LCFA: −33.5 (−32.8)‰ and Δ14C TOC: −129 (−38)‰, LCFA: −134 (−143)‰, respectively. Such estimates will aid in establishing quantitative links between production, export, and burial of OC from...
The Ayeyawady delta is the last Asian megadelta whose evolution has remained essentially unexplor... more The Ayeyawady delta is the last Asian megadelta whose evolution has remained essentially unexplored so far. Unlike most other deltas across the world, the Ayeyawady has not yet been affected by dam construction providing a unique view on largely natural deltaic processes benefiting from abundant sediment loads affected by tectonics and monsoon hydroclimate. To alleviate the information gap and provide a baseline for future work, here we provide a first model for the Holocene development of this megadelta based on radiocarbon and optically stimulated luminescence-dated trench and drill core sediments collected in 2016 and 2017, together with a re-evaluation of published maps, charts and scientific literature. Altogether, this data indicates that Ayeyawady is a mud-dominated delta with tidal and wave influences that has been constructed within a vertically stable Pleistocene incised valley. The sediment-rich Ayeyawady River built meander belt alluvial ridges with avulsive characters. ...
Understanding the transport history and fate of organic carbon (OC) within river systems is cruci... more Understanding the transport history and fate of organic carbon (OC) within river systems is crucial in order to constrain the dynamics and significance of land-ocean interactions as a component of the global carbon cycle. Fluvial export and burial of terrestrial OC in marine sediments influences atmospheric CO 2 over a range of timescales, while river-dominated sedimentary sequences can provide valuable archives of paleoenvironmental information. While there is abundant evidence that the association of organic matter (OM) with minerals exerts an important influence on its stability as well as hydrodynamic behavior in aquatic systems, there is a paucity of information on where such associations form and how they evolve during fluvial transport. Here, we track total organic carbon (TOC) and terrestrial biomarker concentrations (plant wax-derived long-chain fatty acids (FA), branched glycerol dialkyl glycerol tetraethers (brGDGTs) and lignin-derived phenols) in sediments collected along the entire course of the Danube River system in the context of sedimentological parameters. Mineral-specific surface area-normalized biomarker and TOC concentrations show a systematic decrease from the upper to the lower Danube basin. Changes in OM loading of the available mineral phase correspond to a net decrease of 70-80% of different biomolecular components. Ranges for biomarker loadings on Danube River sediments, corresponding to 0.4-1.5 lg FA /m 2 for long-chain (n-C 24-32 ) fatty acids and 17-71 ng brGDGT /m 2 for brGDGTs, are proposed as a benchmark for comparison with other systems. We propose that normalizing TOC as well as biomarker concentrations to mineral surface area provides valuable quantitative constraints on OM dynamics and organo-mineral interactions during fluvial transport from terrigenous source to oceanic sink.
Abundances and distributional changes of branched glycerol dialkyl glycerol tetraethers (brGDGTs)... more Abundances and distributional changes of branched glycerol dialkyl glycerol tetraethers (brGDGTs) in fluvially influenced sediments are used in various paleoclimate studies to reconstruct variations in soil export, continental air temperature and soil pH in corresponding river basins. For accurate interpretation of these records, it is important to understand the provenance and the evolution of biomarker signals as they move through the river system. Here we investigate the brGDGT composition of modern river sediments of the Danube River, the second largest river in Europe. BrGDGT-based mean annual air temperature and soil pH parallel the actual values of air temperature and soil pH from the upper to the lower basin, showing that signals predominantly reflect local as opposed to basin-wide environmental conditions. Furthermore, data generated using the recently developed method with improved chromatography, separating the 6-methyl-isomers from the 5-methyl-isomers, was compared with that resulting from the conventional method. We show that the temperatures and pH values reconstructed using the data obtained by improved chromatography best resemble the local environmental conditions throughout the Danube River basin. Our results highlight the importance of in-depth studies within river systems to better understand the provenance of biomarker signals in fluvially derived sedimentary archives.
Watershed deforestation over the last two millennia led to the rapid expansion and morphological ... more Watershed deforestation over the last two millennia led to the rapid expansion and morphological diversification of the Danube delta (Fig. ) coupled with a complete transformation of the ecosystem in the receiving marine basin, the Black Sea . During this period the central wave-dominated lobe of Sulina was slowly abandoned and the southernmost arm of the Danube, the St. George, was reactivated and started to build its second wave-dominated delta lobe at the open coast. Simultaneously, secondary distributaries branching off from the St. George branch built the Dunavatz bayhead lobe into the southern Razelm lagoon (Fig. ). This intense deltaic activity accompanied drastic changes in Danube's flow regime. Many small deltas had grown during intervals of enhanced anthropogenic pressure in their watersheds . However, finding specific causes, whether natural or anthropogenic, for such a sweeping reorganization of a major delta built by a continental-scale river like Danube requires detailed reconstructions of its depositional history. Here we provide a first look at the Danube's deltaic reorganization along its main distributary, the Chilia, and discuss potential links to hydroclimate, population growth and cultural changes in the watershed. For this reconstruction, we used sediment core-based depositional histories together with a morphological analysis of historical cartographic material and recent satellite photography (see complete methods in Supplementary data). The Chilia arm, which flows along the northern rim of Danube delta (Fig. ), has successively built three lobes and it was first mapped in detail at the end of the 18th century (Fig. ). The depositional architecture of these lobes was controlled by the entrenched drainage pattern formed during the last lowstand in the Black Sea, by the pre-Holocene loess relief developed within and adjacent to this lowstand drainage and by the development of Danube's own deltaic deposits that are older than Chilia's Carozza et al., 2012a). The oldest Chilia lobe (Fig. and) filled the Pardina Anthropocene xxx (2014) xxx-xxx
River deltas are constructed with surplus fluvial sediment that is not washed away by waves and c... more River deltas are constructed with surplus fluvial sediment that is not washed away by waves and currents or drowned by the sea. The waterlogged, low gradient deltaic landscapes favor development of marshes and mangroves, which in turn, contribute organic materials to the delta. In natural conditions, deltas are dynamic systems that adapt to changes in boundary conditions by advancing, retreating, switching, aggrading, and/or drowning. However, most modern deltas are constrained in place by societal needs such as protecting residents, resources, and infrastructure or preserving biodiversity and ecosystem services. Human activities over the last century have inadvertently led to conditions that are unfavorable for deltas . New sediment input has been severely curtailed by trapping behind river dams. Distribution of the remaining sediment load across deltas or along their shores has been altered by engineering works. And accelerating eustatic sea level rise combined with anthropogenic subsidence favors marine flooding that surpasses the normal rate of sediment accumulation, leading in time to permanent drowning of extensive regions of the delta plains. Restoration is envisioned for extensively altered deltas (e.g., , but in these hostile conditions virtually all deltas are becoming unstable and require strategies for maintenance. Availability of sediments is the first order concern for delta maintenance. Sediment budgets are, however, poorly constrained for most deltas (Blum and Roberts, 2009 and references therein). We know that fluvial sediments feed the delta plain (topset) and the nearshore delta front zone (foreset) contributing to aggradation and progradation respectively, but only limited quantitative information exists on the laws governing this sediment partition (Paola et al., 2011 and references therein). Except for deltas built in protective embayments (e.g., , the trapping efficiency appears remarkably small as over 50% of the total load may escape to the shelf and beyond . Therefore, a key strategy for delta maintenance is a deliberate and rational sediment management that would Anthropocene 1 (2013) 35-45
A catastrophic flooding of the Black Sea basin was proposed to have occurred during its reconnect... more A catastrophic flooding of the Black Sea basin was proposed to have occurred during its reconnection to the ocean in the early Holocene. Possible cultural consequences of the flood include the migration of Neolithic farmers from around the Black Sea towards central Europe as well as the creation of flood myths. Stratigraphic and paleo-geomorphologic information from Danube delta aided by radiocarbon ages on articulated mollusks constrain the level in the Black Sea before the marine reconnection to ca 30 m below the present sea level rather than 80 m or lower. If the flood occurred at all, the sea level increase and the flooded area during the reconnection were significantly smaller than previously proposed.
Uploads
Papers by Florin Filip