scholarly journals Mass-movement and flood-induced deposits in Lake Ledro, southern Alps, Italy: implications for Holocene palaeohydrology and natural hazards

2013 ◽  
Vol 9 (2) ◽  
pp. 825-840 ◽  
Author(s):  
A. Simonneau ◽  
E. Chapron ◽  
B. Vannière ◽  
S. B. Wirth ◽  
A. Gilli ◽  
...  
Keyword(s):  
Organic Matter ◽  
Soil Erosion ◽  
Natural Hazards ◽  
Catchment Area ◽  
Central Basin ◽  
Flood Events ◽  
Seismic Profiles ◽  
Terrestrial Organic Matter ◽  
Soil Thickness ◽  
The Holocene

Abstract. High-resolution seismic profiles and sediment cores from Lake Ledro combined with soil and riverbed samples from the lake's catchment area are used to assess the recurrence of natural hazards (earthquakes and flood events) in the southern Italian Alps during the Holocene. Two well-developed deltas and a flat central basin are identified on seismic profiles in Lake Ledro. Lake sediments have been finely laminated in the basin since 9000 cal. yr BP and frequently interrupted by two types of sedimentary events (SEs): light-coloured massive layers and dark-coloured graded beds. Optical analysis (quantitative organic petrography) of the organic matter present in soil, riverbed and lacustrine samples together with lake sediment bulk density and grain-size analysis illustrate that light-coloured layers consist of a mixture of lacustrine sediments and mainly contain algal particles similar to the ones observed in background sediments. Light-coloured layers thicker than 1.5 cm in the main basin of Lake Ledro are synchronous to numerous coeval mass-wasting deposits remoulding the slopes of the basin. They are interpreted as subaquatic mass-movements triggered by historical and pre-historical regional earthquakes dated to AD 2005, AD 1891, AD 1045 and 1260, 2545, 2595, 3350, 3815, 4740, 7190, 9185 and 11 495 cal. yr BP. Dark-coloured SEs develop high-amplitude reflections in front of the deltas and in the deep central basin. These beds are mainly made of terrestrial organic matter (soils and lignocellulosic debris) and are interpreted as resulting from intense hyperpycnal flood event. Mapping and quantifying the amount of soil material accumulated in the Holocene hyperpycnal flood deposits of the sequence allow estimating that the equivalent soil thickness eroded over the catchment area reached up to 5 mm during the largest Holocene flood events. Such significant soil erosion is interpreted as resulting from the combination of heavy rainfall and snowmelt. The recurrence of flash flood events during the Holocene was, however, not high enough to affect pedogenesis processes and highlight several wet regional periods during the Holocene. The Holocene period is divided into four phases of environmental evolution. Over the first half of the Holocene, a progressive stabilization of the soils present through the catchment of Lake Ledro was associated with a progressive reforestation of the area and only interrupted during the wet 8.2 event when the soil destabilization was particularly important. Lower soil erosion was recorded during the mid-Holocene climatic optimum (8000–4200 cal. yr BP) and associated with higher algal production. Between 4200 and 3100 cal. yr BP, both wetter climate and human activities within the drainage basin drastically increased soil erosion rates. Finally, from 3100 cal. yr BP to the present-day, data suggest increasing and changing human land use.

scholarly journals Multidisciplinary distinction of mass-movement and flood-induced deposits in lacustrine environments: implications for Holocene palaeohydrology and natural hazards (Lake Ledro, Southern Alps, Italy)

2012 ◽  
Vol 8 (4) ◽  
pp. 3205-3249 ◽  
Author(s):  
A. Simonneau ◽  
E. Chapron ◽  
B. Vannière ◽  
S. B. Wirth ◽  
A. Gilli ◽  
...  
Keyword(s):  
Organic Matter ◽  
Soil Erosion ◽  
Natural Hazards ◽  
Catchment Area ◽  
Central Basin ◽  
Flood Events ◽  
Seismic Profiles ◽  
Terrestrial Organic Matter ◽  
Soil Thickness ◽  
The Holocene

Abstract. High-resolution seismic profiles and sediment cores from Lake Ledro combined with soil and river-bed samples from the lake's catchment area are used to assess the recurrence of natural hazards (earthquakes and flood events) in the southern Italian Alps during the Holocene. Two well-developed deltas and a flat central basin are identified on seismic profiles in Lake Ledro. Lake sediments are finely laminated in the basin since 9000 cal. yr BP and frequently interrupted by two types of sedimentary events: light-coloured massive layers and dark-coloured graded beds. Optical analysis (quantitative organic petrography) of the organic matter occurring in soils, river beds and lacustrine samples together with lake-sediment bulk density and grain-size analysis illustrate that light-coloured layers consist of a mixture of lacustrine sediments and mainly contain algal particles similar to the ones observed in background sediments. Light-coloured layers thicker than 1.5 cm in the main basin of Lake Ledro are dense and synchronous to numerous coeval mass-wasting deposits remoulding the slopes of the basin. They are interpreted as subaquatic mass movements triggered by historical and pre-historical regional earthquakes dated to 2005 AD, 1891 AD, 1045 AD and 1260, 2545, 2595, 3350, 3815, 4740, 7190, 9185 and 11495 cal. yr BP. Dark-coloured sedimentary event are dense and develop high-amplitude reflections in front of the deltas and in the deep central basin. These beds are mainly made of terrestrial organic matter (soils and ligno-cellulosic debris) and are interpreted as resulting from intense hyperpycnal flood events. Mapping and quantifying the amount of soil material accumulated in the Holocene hyperpycnal flood deposits of the sequence and applying the De Ploey erosion model allow estimating that the equivalent soil thickness eroded over the catchment area reached up to 4 mm during the largest Holocene flood events. Such significant soil erosion is interpreted as resulting from the combination of heavy rainfall and snowmelt. The recurrence of flash-flood events during the Holocene was however not high enough to affect pedogenesis processes and highlight several wet regional periods during the Holocene. The Holocene period is divided into four phases of environmental evolution. Over the first half of the Holocene, a progressive stabilization of the soils present through the catchment of Lake Ledro was associated with a progressive reforestation of the area and only interrupted during the wetter 8.2 event when the soil destabilization was particularly important. Lower soil erosion was recorded during the Mid-Holocene climatic optimum (8000–4200 cal. yr BP) and associated with higher algal production. Between 4200 and 3100 cal. yr BP, both wetter climate and human activities within the drainage basin drastically increased soil erosion rates. Finally, from 3100 cal. yr BP to the present-day, results suggest increasing and changing human land-use.

Lake Wabamun, Alta.: a paleoenvironmental study

1984 ◽  
Vol 62 (7) ◽  
pp. 1438-1465 ◽  
Author(s):  
M. Hickman ◽  
C. E. Schweger ◽  
T. Habgood
Keyword(s):  
Organic Matter ◽  
Catchment Area ◽  
Benthic Algae ◽  
Climatic Changes ◽  
Water Levels ◽  
Sedimentary Organic Matter ◽  
Tephra Layer ◽  
The Holocene ◽  
Fossil Pigments ◽  
The Core

Results from paleoenvironmental investigations of Lake Wabamun, Alta. (longitudes 114°26′ and 114°44′ W; latitudes 50°30′ and 53°35′ N), show that the sedimentary record spans the Holocene period in the case of the core taken from the deepest portion of the lake (the Seba core), while the record from the shallow Moonlight Bay spans a somewhat shorter interval. Basically, the lake has changed little during the last 4000 years except for increases in submersed hydrophytes in Moonlight Bay and undoubtedly other shallow regions of the lake. Production, too, has changed little during this interval except in Moonlight Bay, where hydrophytes and benthic algae contributed more to the sedimentary organic matter and fossil pigments. The deposition of the Mt. Mazama tephra in the catchment area and lake at 6600 years BP may have had a profound effect upon the lake. Increased turbidity occurred. This together with climatic changes including increased precipitation and catchment-area instability caused rapid infilling of the lake and low production. Moreover, prior to deposition of the tephra layer, water levels were lower and the water was more saline with Ruppia present, a feature found in other lakes in Alberta during the Hypsithermal period. Finally, prior to this period the lake was similar to its present day condition except during its very beginning when more turbid conditions prevailed.

scholarly journals Soil Erodibility Analysis and Mapping in Gilgel Gibe-I Catchment, Omo-Gibe River Basin, Ethiopia

2021 ◽  
Vol 2021 ◽  
pp. 1-7
Author(s):  
Gizaw Tesfaye ◽  
Tolesa Ameyu
Keyword(s):  
Organic Matter ◽  
Soil Organic Matter ◽  
Soil Erosion ◽  
Catchment Area ◽  
Soil Structure ◽  
Soil Erodibility ◽  
Soil Permeability ◽  
Fine Grained ◽  
Fine Grained Soil ◽  
Texture Class

The soil erosion factor, erodibility, measures the susceptibility of soil particles to transport and detachment by erosive agents. Soil erosion and sedimentation models use soil properties and erodibility as the main input. However, in developing countries such as Ethiopia, data on soil erosion and soil-related properties are limited. For this reason, different researchers use different data sources that are adopted from a large scale and come with very different results. For this reason, the study was proposed to analyze and map the soil erodibility of the catchment area using primary data. 80 mixed soil samples were taken from the catchment with GPS coordinates and analyzed in the laboratory for soil texture class and soil organic matter. Accordingly, sandy clay loam is a dominant soil texture class covering 65% of the catchment area with 2.46% average soil organic matter, which is high in the mountainous part and lower in the lower valley of the catchment area. Most of the catchment area, which accounts for more than 78% of the area, was dominated by medium- or coarse-grained soil structure, and in the upper parts of the catchment area, 21% of the catchment area was covered with fine-grained soil structure. Similarly, 66% of the catchment area was covered with slow to moderate soil permeability, followed by slow soil permeability covering 21% of the area. Finally, the soil erodibility value of the Gilgel Gibe-I catchment was determined to be 0.046 ton h·MJ−1·mm−1 with a range of 0.032 to 0.063 ton·h·MJ−1·mm−1. In general, soils with slow permeability, high silt content, and medium- to fine-grained soil structures are the most erodible. They are conveniently separate; they tend to crust and form high drainage. Knowing this, the catchment has a moderate soil erodibility value. Thus, the study recommends evidence of land cover and the protection of arable land through suitable soil and water protection measures to improve soil permeability and soil structure.

scholarly journals Characterization of particulate organic matter in the Lena River Delta and adjacent nearshore zone, NE Siberia – Part 1: Lignin-derived phenol compositions

2014 ◽  
Vol 11 (10) ◽  
pp. 14359-14411 ◽  
Author(s):  
M. Winterfeld ◽  
M. A. Goñi ◽  
J. Just ◽  
J. Hefter ◽  
G. Mollenhauer
Keyword(s):  
Organic Matter ◽  
Climate Warming ◽  
Catchment Area ◽  
Surface Sediments ◽  
The Arctic ◽  
Terrestrial Organic Matter ◽  
Small Catchment ◽  
Lena River ◽  
Diagenetic Alteration ◽  
Phenol Composition

Abstract. The Lena River in central Siberia is one of the major pathways translocating terrestrial organic matter (OM) from its vast catchment area to the coastal zone of the Laptev Sea and the Arctic Ocean. The permafrost soils of its far south stretching catchment, which store huge amounts of OM, will most likely respond differently to climate warming and remobilize previously frozen OM with distinct properties specific for the source vegetation and soil. To characterize the material discharged by the Lena River, we analyzed the lignin phenol composition in total suspended matter (TSM) from surface water collected in spring and summer, surface sediments from the Buor Khaya Bay along with soils from the Lena Delta's first (Holocene) and third terraces (Pleistocene ice complex), and plant samples. Our results show that lignin-derived cinnamyl:vanillyl (C/V) and syringyl:vanillyl (S/V) ratios are >0.14 and 0.25, respectively, in TSM and surface sediments, whereas in delta soils they are >0.16 and >0.51, respectively. These lignin compositions are consistent with significant inputs of organic matter from non-woody angiosperm sources mixed with organic matter derived from woody gymnosperm sources. We applied a simple linear mixing model based on the C/V and S/V ratios and the results indicate the organic matter in delta TSM samples and Buor Khaya Bay surface sediments contain comparable contributions from gymnosperm material, which is primarily derived from the taiga forests south of the delta, and angiosperm material typical for tundra vegetation. Considering the small catchment area covered by tundra (∼12%), the input is substantial and tundra-derived OM input is likely to increase in a warming Arctic. The similar and high acid to aldehyde ratios of vanillyl and syringyl (Ad/AlV, S) in Lena Delta summer TSM (>0.7 and >0.5, respectively) and Buor Khaya Bay surface sediments (>1.0 and >0.9, respectively) suggest that the OM is highly degraded and Lena River summer TSM could be a possible source for the surface sediments. The Ad/AlV, S ratios of the first and third delta terraces were generally lower (mean ratios >0.4 and >0.4, respectively) than summer TSM and surface sediments. This implies that TSM contains additional contributions from a more degraded OM source (southern catchment and/or finer more degraded particle size). Alternatively, OM degradation on land after permafrost thawing and subaqueously during transport and sedimentation could be considerable. Despite the high natural heterogeneity of OM stored in delta soils and exported by the Lena River, the catchment characteristic vegetation is reflected by the lignin biomarker composition. Climate warming related changes in the Lena River catchment may be detectable in changing lignin biomarker composition and diagenetic alteration.

Biomarker evidence for changes in terrestrial organic matter input into the Yellow Sea mud area during the Holocene

2016 ◽  
Vol 59 (6) ◽  
pp. 1216-1224 ◽  
Author(s):  
Peng Wu ◽  
XiaoTong Xiao ◽  
ShuQin Tao ◽  
ZuoSheng Yang ◽  
HaiLong Zhang ◽  
...  
Keyword(s):  
Organic Matter ◽  
Yellow Sea ◽  
The Yellow Sea ◽  
Terrestrial Organic Matter ◽  
The Holocene ◽  
Sea Mud ◽  
Mud Area ◽  
Organic Matter Input

Impact of flood events on the transport of terrestrial organic matter to the ocean: A study of the Têt River (SW France) using the BIT index

2007 ◽  
Vol 38 (10) ◽  
pp. 1593-1606 ◽  
Author(s):  
Jung-Hyun Kim ◽  
Wolfgang Ludwig ◽  
Stefan Schouten ◽  
Philippe Kerhervé ◽  
Lydie Herfort ◽  
...  
Keyword(s):  
Organic Matter ◽  
Flood Events ◽  
Terrestrial Organic Matter ◽  
Sw France

scholarly journals Characterization of particulate organic matter in the Lena River delta and adjacent nearshore zone, NE Siberia – Part 2: Lignin-derived phenol compositions

2015 ◽  
Vol 12 (7) ◽  
pp. 2261-2283 ◽  
Author(s):  
M. Winterfeld ◽  
M. A. Goñi ◽  
J. Just ◽  
J. Hefter ◽  
G. Mollenhauer
Keyword(s):  
Organic Matter ◽  
Climate Warming ◽  
Catchment Area ◽  
Surface Sediments ◽  
The Arctic ◽  
Terrestrial Organic Matter ◽  
Small Catchment ◽  
Lena River ◽  
Diagenetic Alteration ◽  
Phenol Composition

Abstract. The Lena River in central Siberia is one of the major pathways translocating terrestrial organic matter (OM) from its vast catchment area to the coastal zone of the Laptev Sea and the Arctic Ocean. The permafrost soils of its far south-stretching catchment, which store huge amounts of OM, will most likely respond differently to climate warming and remobilize previously frozen OM with distinct properties specific for the source vegetation and soil. To characterize the material discharged by the Lena River, we analyzed the lignin phenol composition in total suspended matter (TSM) from surface water collected in spring and summer, surface sediments from Buor Khaya Bay along with soils from the Lena Delta's first (Holocene) and third terraces (Pleistocene ice complex), and plant samples. Our results show that lignin-derived cinnamyl : vanillyl (C / V) and syringyl : vanillyl (S / V) ratios are > 0.14 and 0.25, respectively, in TSM and surface sediments, whereas in delta soils they are > 0.16 and > 0.51, respectively. These lignin compositions are consistent with significant inputs of organic matter from non-woody angiosperm sources mixed with organic matter derived from woody gymnosperm sources. We applied a simple linear mixing model based on the C / V and S / V ratios, and the results indicate the organic matter in delta TSM samples and Buor Khaya Bay surface sediments contain comparable contributions from gymnosperm material, which is primarily derived from the taiga forests south of the delta, and angiosperm material typical for tundra vegetation. Considering the small catchment area covered by tundra (~ 12%), the input is substantial and tundra-derived OM input is likely to increase in a warming Arctic. The similar and high acid to aldehyde ratios of vanillyl and syringyl (Ad / AlV, S) in Lena Delta summer TSM (> 0.7 and > 0.5, respectively) and Buor Khaya Bay surface sediments (> 1.0 and > 0.9, respectively) suggest that the OM is highly degraded and Lena River summer TSM could be a possible source of the surface sediments. The Ad / AlV, S ratios of the first and third delta terraces were generally lower (mean ratios > 0.4 and > 0.4, respectively) than summer TSM and surface sediments. This implies that TSM contains additional contributions from a more degraded OM source (southern catchment and/or finer more degraded particle size). Alternatively, OM degradation on land after permafrost thawing and subaqueously during transport and sedimentation could be considerable. Despite the high natural heterogeneity of OM stored in delta soils and exported by the Lena River, the catchment-characteristic vegetation is reflected by the lignin biomarker composition. Climate-warming-related changes in the Lena River catchment may be detectable in changing lignin biomarker composition and diagenetic alteration.

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