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 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 The Use of Carbon Isotopes (13C,14C) in Soil to Evaluate Vegetation Changes During the Holocene in Central Brazil

Radiocarbon ◽  
1996 ◽  
Vol 38 (2) ◽  
pp. 191-201 ◽  
Author(s):  
L. C. R. Pessenda ◽  
Ramon Aravena ◽  
A. J. Melfi ◽  
E. C. C. Telles ◽  
René Boulet ◽  
...  
Keyword(s):  
Organic Matter ◽  
Carbon Isotopes ◽  
Climate Changes ◽  
Climatic Changes ◽  
Soil Profiles ◽  
Vegetation Changes ◽  
Subtropical Region ◽  
The Holocene ◽  
Central Brazil ◽  
Savanna Vegetation

This paper presents carbon isotope data measured in three soil profiles from the Salitre area, Central Brazil. The study forms part of a research project on tropical and subtropical soils in Brazil, in which the main objective is to use carbon isotopes to provide information about vegetation changes that have occurred in relation to climate changes during the Holocene. 14C data from charcoal samples and soil organic matter (SOM) indicate that the organic matter in the soils studied is of Holocene age at least. Furthermore, the presence of a significant amount of charcoal in the soils suggests that forest fire was a significant ocurrence during the Holocene and probably had an important role in determining the dynamics of forest vegetation in the study area. Correspondingly, 13C data indicate that C3 plants provided the dominant vegetation of the study area, even during the dry periods when savanna vegetation is supposed to have replaced the forest communities. This study contributes to our better understanding of the relation between climatic changes and vegetation in the subtropical region of Brazil.

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.

Amino acids and amino sugars as indicators of the source and degradation state of sedimentary organic matter

2021 ◽  
Vol 230 ◽  
pp. 103931
Author(s):  
Jin-E Wei ◽  
Yan Chen ◽  
Jian Wang ◽  
Shi-Bo Yan ◽  
Hong-Hai Zhang ◽  
...  
Keyword(s):  
Amino Acids ◽  
Organic Matter ◽  
Sedimentary Organic Matter ◽  
Amino Sugars ◽  
Degradation State

scholarly journals Difference Analysis of Organic Matter Enrichment Mechanisms in Upper Ordovician-Lower Silurian Shale from the Yangtze Region of Southern China and Its Geological Significance in Shale Gas Exploration

Geofluids ◽  
2019 ◽  
Vol 2019 ◽  
pp. 1-14 ◽  
Author(s):  
Ming Wen ◽  
Zhenxue Jiang ◽  
Kun Zhang ◽  
Yan Song ◽  
Shu Jiang ◽  
...  
Keyword(s):  
Organic Matter ◽  
Shale Gas ◽  
Southern China ◽  
Sedimentary Organic Matter ◽  
Gas Content ◽  
Silicon Isotope ◽  
Upper Ordovician ◽  
Lower Silurian ◽  
Excess Silicon ◽  
Lower Yangtze

The upper Ordovician-lower Silurian shale has always been the main target of marine shale gas exploration in southern China. However, the shale gas content varies greatly across different regions. The organic matter content is one of the most important factors in determining gas content; therefore, determining the enrichment mechanisms of organic matter is an important problem that needs to be solved urgently. In this paper, upper Ordovician-lower Silurian shale samples from the X-1 and Y-1 wells that are located in the southern Sichuan area of the upper Yangtze region and the northwestern Jiangxi area of the lower Yangtze region, respectively, are selected for analysis. Based on the core sample description, well logging data analysis, mineral and elemental composition analysis, silicon isotope analysis, and TOC (total organic carbon) content analysis, the upper Ordovician-lower Silurian shale is studied to quantitatively calculate its content of excess silicon. Subsequently, the results of elemental analysis and silicon isotope analysis are used to determine the origin of excess silicon. Finally, we used U/Th to determine the characteristics of the redox environment and the relationship between excess barium and TOC content to judge paleoproductivity and further studied the mechanism underlying sedimentary organic matter enrichment in the study area. The results show that the excess silicon from the upper Ordovician-lower Silurian shale in the upper Yangtze area is derived from biogenesis. The sedimentary water body is divided into an oxygen-rich upper water layer that has higher paleoproductivity and a strongly reducing lower water that is conducive to the preservation of sedimentary organic matter. Thus, for the upper Ordovician-lower Silurian shale in the upper Yangtze region, exploration should be conducted in the center of the blocks with high TOC contents and strongly reducing water body. However, the excess silicon in the upper Ordovician-lower Silurian shale of the lower Yangtze area originates from hydrothermal activity that can enhance the reducibility of the bottom water and carry nutrients from the crust to improve paleoproductivity and enrich sedimentary organic matter. Therefore, for the upper Ordovician-lower Silurian shale in the lower Yangtze region, exploration should be conducted in the blocks near the junction of the two plates where hydrothermal activity was active.

scholarly journals Molecular characterization of suspended and sedimentary organic matter in an Arctic delta

1996 ◽  
Vol 41 (3) ◽  
pp. 488-497 ◽  
Author(s):  
S. Peulvé ◽  
M.-A. Sicre ◽  
A. Saliot ◽  
J. W. De Leeuw ◽  
M. Baas
Keyword(s):  
Organic Matter ◽  
Molecular Characterization ◽  
Sedimentary Organic Matter
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