Post-glacial Environmental Change as Recorded by Silver Lake Sediments, Logan County, Ohio PDF Download
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Author: Dawit D. Yifru
Publisher:
ISBN:
Category : Geology
Languages : en
Pages : 198
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Author: Dawit D. Yifru
Publisher:
ISBN:
Category : Geology
Languages : en
Pages : 198
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Author: Cathy Lee Weiss
Publisher:
ISBN:
Category : Ecology
Languages : en
Pages : 174
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Author: Cathy Lee Weiss
Publisher:
ISBN:
Category : Diatoms
Languages : en
Pages : 108
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Author: Kelly A. Shaw
Publisher:
ISBN:
Category : Eutrophication
Languages : en
Pages : 164
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The increase in human population and human activities often negatively impacts the quality of our waters. Lake sediment often preserves a record of past anthropogenic activities and can be used to assess the impact of humans on the lake system. This study examines Silver Lake, a groundwater-fed kettle lake located in the Village of Silver Lake, Summit County, Ohio. Surface samples and water column profiles were collected to assess present-day conditions because the health of the lake is of concern to the local residents. The lake is eutrophic, with an anoxic hypolimnion during the summer months that allows phosphorus to be released from the sediment. Since 1982 lake transparency has been decreasing as evidenced by a shallowing in Secchi depth reading. Silver Lake contains two basins, and sediment cores were collected from both basins to assess longterm changes in the lake. The sediment in both basins displayed similar trends. Below 163.5 centimeters below lake floor core depth, a dark green-brown, organic-rich gyttja with relatively high C/N ratio is interpreted to represent forested watershed conditions prior to the arrival of New Englanders in 1804. The decline in sediment organic content and corresponding increase in bulk density at 125 cmblf likely reflects the impact of land clearance within the watershed following settlement. Between 79 -117.5 cmblf, a black mud having an oily odor and low organic content is present. This black mud has pronounced increases in trace metals, ferrimagnetic content, combustion particles, and bulk density, and likely was deposited between 1874 and 1918 when a major amusement park, complete with steamboat rides, occupied the western shore of the lake. This period is also inferred to contain the 1913 flood shown by an increase in Cr content. When the park closed in 1918, the land was converted into suburban housing and by the mid-late 20th century the entire watershed was occupied by suburban housing. The brown mud above 79 cmblf core depth displays decreasing trends in ferrimagnetic content, tracemetal content, and combustion particles, reflecting changes in anthropogenic activities during the mid- to late 20th century. Study of the lake sediment allows the impacts of humans on the Silver Lake system to be assessed and the present-day conditions to be placed in a long-term context.
Author: Corinne M. Lally
Publisher:
ISBN:
Category : Lake sediments
Languages : en
Pages : 216
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To provide greater spatial coverage of late Pleistocene to Holocene environmental change in the Midwestern United States, a 1350 cm long sediment core was collected from Silver Lake in northeast Ohio. Age control was provided by new radiocarbon dates, correlation to a dated lake record from western Ohio, and a prior study of Silver Lake. Lithologic descriptions and sedimentary profiles of dry bulk density (DBD), organic matter (OM), carbonate, C/N, grain size, magnetic properties, and concentrations of terrigenous derived elements (Al, Ti, and K) allow the core to be divided into six periods. The climate interpretations are compared to published regional and hemispheric climate records. The first period is Deglaciation, which spans from 17,560 -- 13,600 cal year BP (1353 - 1188 centimeters below lake floor (cmblf)). Silty sediment with low OM (average 6 %) and high DBD (average 0.832 g/cm3) are interpreted to reflect cold conditions soon after deglaciation. The Latest Pleistocene Period is the second period and spans from 13,600 -- 12,200 cal yr BP (1188 -- 1103 cmblf). Brown to light brown mud with silty layers, a slight increase in % OM (average 9 %) and decrease in DBD (average 0.694 g/cm3) characterize this interval. The Latest Pleistocene Period may have been a time of increased primary productivity in Silver Lake. The third period is the Younger Dryas, which spans from 12,200 -- 11,500 cal yr BP (1103 -- 1070 cmblf). Gray-brown to light-brown silty mud having low % OM (average 6%), high DBD (average 0.703 g/cm3), high concentrations of magnetic minerals, and elevated concentrations of Al, Ti, and K characterize this period. These sediment characteristics are interpreted as cold and dry conditions, increased terrigenous input, and/or decreased primary productivity. The fourth period is the Early Holocene which spans from 11,500 -- 7,450 cal yr BP (1070 -- 824 cmblf), and is divided into two subperiods. During the first subperiod, from 11,500 -- 10,600 cal yr BP (1070 -- 1016 cmblf), there was an increase in % OM (average 28 %) and decrease in DBD (average 0.311 g/cm3) and concentrations of Al, Ti, and K. The first subperiod of the Early Holocene is interpreted to be a period of brief warming. The second subperiod of the Early Holocene spans from 10,600 -- 7,450 cal yr BP (1016-824 cmblf), and is characterized by highly variable % OM and DBD and increased Al, Ti, and K. This subperiod is interpreted as a period of increased aridity. The fifth period is the Mid to Late Holocene which spans from 7,450 -- 200 cal yr BP (824 -- 128 cmblf). Alternating brown and dark brown mud having no visible silty layers, high % OM (average 51%), low DBD (average 0.116 g/cm3), and decreased Al, Ti, and K and magnetic concentration characterize this period. These sediment characteristics are interpreted to reflect warm and moist conditions when primary productivity increased and/or terrigenous influx decreased. However, within the Mid to Late Holocene Period there are six pronounced intervals of decreased % OM and increased Al, Ti, and K suggestive of millennial-scale increases in terrigenous input and/or decreases in lake productivity. These six intervals may be related in part to rapid global climate changes during the Holocene, when temperatures and moisture balance fluctuated. The sixth period is the Anthropogenic Period, which spans from 200 cal yr BP to the present (128 -- 0 cmblf). The Anthropogenic Period is characterized by a pronounced decrease in % OM (average 19%), increase in DBD (average 0.273 g/cm3), and an increase in the mass accumulation rate (MAR) resulting from Euro-American land clearance enhancing watershed erosion.
Author: Liam Michael Reidy
Publisher:
ISBN:
Category :
Languages : en
Pages : 108
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This study focuses on the history of natural and human-induced environmental change as recorded in the sediments of two lakes: Mountain Lake in the Presidio National Park, San Francisco, California and Big Soda Lake, near Fallon, Churchill County, Nevada. The records of these lakes examined in this study cover approximately the last 2,000 years. Sediment cores from the lakes were dated with radiocarbon, lead-210, plutonium 240/239, tephrachronology, and the first appearance of non-native pollen types. The cores were analyzed to determine changes in stable isotopes (carbon and oxygen), sediment chemistry, fossil pollen, magnetic susceptibility, organic content, and brine shrimp cyst concentrations. Big Soda Lake has been the subject of scientific investigation since the 19th Century and two famous scientists have previously worked at the site. First, the geologist, Israel Russell explored the lake in 1882 as part of his work on Pleistocene Lake Lahontan and provided the first scientific report on the lake. Later in 1933, Evelyn Hutchinson, the famous Yale limnologist, provided the first detailed limnological report for the lake. More recently in the 1980's, the lake has been studied by scientists from the United States Geological Survey. However, prior to the research reported on here, very little was known of the history of the lake or to what extent its sediments contained a useful record of environmental change. The sediments of Big Soda Lake provide clear evidence for both natural and human-induced environmental change during the past 1600 years. The climate record developed from the analyses of stable isotopes of oxygen and carbon, sediment chemistry, and the concentrations of brine shrimp cysts show several significant shifts in climate. The early part of the record from A.D. 400-850 is period marked by a fluctuating climate, with alternating wet/dry phases each lasting several decades each (40-60 years). During the period known as the Medieval Climate Anomaly (MCA)(A.D. 850-1400), we observe at least two relatively dry periods from A.D. 850-1150 and A.D. 1260-1400. Between the two dry phases, there is a pronounced wet period from A.D. 1150-1260. This wet period matches fairly well with evidence presented in other paleoenvironmental studies in the western Great Basin. During the Little Ice Age (LIA), the evidence indicates that the Big Soda Lake area was not always colder and/or wetter, but that it was in fact drier and perhaps warmer from A.D. 1400-1700 than it had been in the previous millennium. Pronounced dry phases were observed around A.D. 1400, A.D. 1500 and A.D. 1650. The wettest period during the LIA came between A.D. 1750-1800. The human impact record at Big Soda Lake developed from the analyses of stable isotopes of oxygen and carbon, sediment chemistry, and the concentrations of brine shrimp cysts show several dramatic changes in and around the lake since Anglo American settlement of the area began, in the 1850's. Several human impacts have been identified, including regional mining activity, soda salt extraction from the lake, and irrigation induced rising groundwater levels in the last century. Two of these events have dramatically impacted the lake in that time. Firstly, the development of a commercial soda manufacturing and processing facility at the lake beginning in 1875 until the early 20th century; and secondly, the development of irrigation agriculture which led to an 18 m rise in lake level in the first few decades of the twentieth century. The sediments at Mountain Lake provide evidence of unprecedented heavy metal contamination at the San Francisco Presidio during the past 60 years. The lake evidence is consistent with local land-use changes initiated by the arrival of Europeans in the area after 1776 and the construction of California State Highway 1 adjacent to the lake in the late 1930's. The study shows how small water bodies alongside roads can concentrate heavy metals and demonstrates the need for careful scientific investigation of sediments earmarked for dredging to determine what if any contaminants are present. A key outcome of the Mountain Lake research carried out as part of this dissertation was that in the Fall of 2011 a Federal judge ordered the California Department of Transportation (Caltrans) to pay 13.5 million dollars to the Presidio Trust so that the contaminated sediments could be removed and further run-off from the road be prevented from entering the lake.
Author: Adrian David Thompson
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Author: Alice Simms Williams
Publisher:
ISBN:
Category : Paleobotany
Languages : en
Pages : 36
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Author: Roger Yates Anderson
Publisher:
ISBN:
Category : Geology
Languages : en
Pages : 28
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Lakes in North America that are meromictic or that contain sediments with annual layers are assessed for their potential for reconstruction of ancient climates.
Author: R. M. Cline
Publisher: Geological Society of America
ISBN: 0813711452
Category : Science
Languages : en
Pages : 636
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