Stephanodiscus Ehr. species from Holocene sediments in the Faiyum Depression (Middle Egypt)

Lake Qarun in the Egyptian Faiyum Depression is the shrunken remnant of a much larger lake. To investigate the sedimentary history of the former lake, several continuous lacustrine sediment cores were collected from now terrestrial locations within the basin. The suitability of these sediments for reconstructing past environmental changes was first assessed by describing the gross stratigraphies of three core sequences and secondly by evaluating taxonomic issues concerning sedimentary diatom species within the genus, Stephanodiscus Ehr. The stratigraphic descriptions show basal sections comprised of either coarse sand or weathered Ecocene limestone overlain by lacustrine sediments. Lower sections of the lacustrine sediments are diatom marls, and, in the two lakeside cores, these are laminated. These sections indicate that the lake initially formed by rapid in filling to a considerable depth with freshwater and the diatom-rich marls containing abundant Stephanodiscus and Aulacoseira Thwaites species. A new species and variety of Stephanodiscus, S. neoaegypticus and S. neoaegypticus var. fekrii, are described from the marl section in one core. Another species, S. galileenis Håkansson & Erhlich, was also present and is re-evaluated with reference to the published description. The importance of establishing a sound taxonomic foundation for palaeolimnological studies of Lake Qarun is stressed.

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Penguin occupation in the Vestfold Hills

Antarctic Science ◽

10.1017/s095410200800165x ◽

2008 ◽

Vol 21 (2) ◽

pp. 131-134 ◽

Cited By ~ 11

Author(s):

Tao Huang ◽

Liguang Sun ◽

Yuhong Wang ◽

Renbin Zhu

Keyword(s):

Sediment Core ◽

Environmental Changes ◽

Sediment Cores ◽

East Antarctica ◽

Before Present ◽

The Holocene ◽

History Of ◽

Vestfold Hills ◽

Free Area ◽

Ornithogenic Sediment

AbstractDuring CHINARE-22 (December 2005–March 2006), we investigated six penguin colonies in the Vestfold Hills, East Antarctica, and collected several penguin ornithogenic sediment cores, samples of fresh guano and modern penguin bone and feather. We selected seven penguin bones and feathers and six sediments from the longest sediment core and performed AMS14C dating. The results indicate that penguins occupied the Vestfold Hills as early as 8500 calibrated years before present (cal. yrbp), following local deglaciation and the formation of the ice free area. This is the first report on the Holocene history of penguins in the Vestfold Hills. As in other areas of Antarctica, penguins occupied this area as soon as local ice retreated and the ice free area formed, and they are very sensitive to climatic and environmental changes. This work provides the foundation for understanding the history of penguins occupation in Vestfold Hills, East Antarctica.

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Lake Lerna: investigating Hercules' ancient myth

10.5194/egusphere-egu2020-1045 ◽

2020 ◽

Author(s):

Danae Thivaiou ◽

Efterpi Koskeridou ◽

Christos Psarras ◽

Konstantina Michalopoulou ◽

Niki Evelpidou ◽

...

Keyword(s):

Environmental Changes ◽

Coarse Sand ◽

Natural Environments ◽

Aegean Area ◽

Freshwater Gastropods ◽

The Core ◽

Interdisciplinary Field ◽

The People ◽

History Of ◽

Age Model

Greece and the Aegean area are among the first areas in Europe to have been occupied by humans. The record of human interventions in natural environments is thus particularly rich. Some of the interventions of the people inhabiting various localities of the country have been recorded in local mythology. Through the interdisciplinary field of geomythology it is possible to attempt to uncover the relationships between the geological history of early civilizations and ancient myths.In the present work, we focused on the history of Lake Lerni in the Eastern Peloponnese, an area that is better known through the myth of Hercules and the Lernaean Hydra. The area of the lake &#8211; now dried and cultivated &#8211; was part of a karstic system and constituted a marshland that was a source of diseases and needed to be dried.A new core is studied from the area of modern-day Lerni using palaeontological methods in order to reconstruct environmental changes that occurred during the last 6.000 years approximately. The area is known to have gone from marsh-lacustrine environments to dryer environments after human intervention or the intervention of Hercules according to mythology. Levels of peat considered to represent humid intervals were dated using the radiocarbon method so as to have an age model of the core. Samples of sediment were taken every 10 cm; the grain size was analysed for each sample as well as the fossil content for the environmental reconstruction.The presence of numerous freshwater gastropods reflects the intervals of lacustrine environment accompanied with extremely fine dark sediment. Sedimentology is stable throughout the core with few levels of coarse sand/fine gravel, only changes in colour hint to multiple levels richer in organic material.

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Benthic foraminiferal assemblages of the imperial harbor of Claudius (Rome): Further paleoenvironmental and geoarcheological evidences

The Holocene ◽

10.1177/0959683611405239 ◽

2011 ◽

Vol 21 (8) ◽

pp. 1245-1259 ◽

Cited By ~ 15

Author(s):

Letizia Di Bella ◽

Piero Bellotti ◽

Virgilio Frezza ◽

Luisa Bergamin ◽

Maria Gabriella Carboni

Keyword(s):

Middle Ages ◽

Environmental Changes ◽

Sediment Cores ◽

Water Environment ◽

River Mouth ◽

Paleoenvironmental Reconstruction ◽

Tiber River ◽

Comprehensive Picture ◽

History Of ◽

Brackish Water Environment

This paper presents a paleoenvironmental reconstruction of historical development in the area of the ancient harbor of Claudius based on micropaleontological and sedimentological data. Benthic foraminifera are reliable tools for this kind of research because they are sensitive to short-time environmental changes induced by both natural and anthropogenic events. By studying eight sediment cores collected from different sections of the harbor, it was possible to reconstruct a comprehensive picture of the harbor complex. Qualitative and quantitative analysis of foraminiferal associations and sedimentological data, along with radiocarbon dating, were useful to identify three key intervals in the history of the coastal area where the harbor developed. The first interval, located at the bottom of all cores, is characterized by a brackish water environment, corresponding to the formation of the first deltaic cusp of the Tiber River. The second interval is characterized by the harbor activities that developed after a general increase in water depth due to a diversion of the Tiber River mouth. The third interval marks the final phase of harbor activities and the subsequent filling of Claudius’ basin. However, a link with the inner Trajanus’ basin was maintained via the central part of the basin, which remained submerged longer, until the early Middle Ages.

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Vegetation history of Central Chukotka deduced from permafrost paleoenvironmental records of the El'gygytgyn Impact Crater

Climate of the Past Discussions ◽

10.5194/cpd-8-1409-2012 ◽

2012 ◽

Vol 8 (2) ◽

pp. 1409-1441 ◽

Cited By ~ 3

Author(s):

A. A. Andreev ◽

E. Morozova ◽

G. Fedorov ◽

L. Schirrmeister ◽

A. A. Bobrov ◽

...

Keyword(s):

Impact Crater ◽

Environmental Changes ◽

Vegetation History ◽

Lacustrine Sediments ◽

Plant Macrofossils ◽

Early Holocene ◽

Shrub Tundra ◽

Dwarf Birch ◽

History Of ◽

Palynological Study

Abstract. Frozen sediments from three cores bored in permafrost surrounding of the El'gygytgyn Impact Crater Lake have been studied for pollen, non-pollen palynomorphs, plant macrofossils, and rhizopods. The palynological study of the cores contributes to a higher resolution of time intervals presented in a poor temporal resolution in the lacustrine sediments; namely the Allerød and succeeding periods. Moreover, permafrost records better reflect local environmental changes, thus, allowing more reliable reconstruction of the local paleoenvironments. The new data confirm that shrub tundra with dwarf birch, shrub alder and willow dominated in the lake surroundings during the Allerød warming. Younger Dryas pollen assemblages reflect abrupt changes to grass-sedge-herb dominated environments reflecting significant climate deterioration. Low shrub tundra with dwarf birch and willow dominate the lake vicinity at the onset of the Holocene. The founds of larch seeds indicate its local presence around 11 000 cal. yr BP and, thus a northward shift of treeline by about 100 km during the early Holocene thermal optimum. Forest tundra with larch and shrub alder stands grew in the area during the early Holocene. After ca. 3500 cal. yr BP similar-to-modern plant communities became common in the lake vicinity.

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An initial palaeosalinity history of Jaw Lake, Bunger Hills based on a diatom–salinity transfer function applied to sediment cores

Antarctic Science ◽

10.1017/s0954102000000225 ◽

2000 ◽

Vol 12 (2) ◽

pp. 172-176 ◽

Cited By ~ 13

Author(s):

D. Roberts ◽

A. McMinn ◽

D. Zwartz

Keyword(s):

Transfer Function ◽

Environmental History ◽

Lake Water ◽

Sediment Cores ◽

Lacustrine Sediments ◽

Lake Basin ◽

Large Step ◽

History Of ◽

Adequate Representation ◽

Vestfold Hills

Two sediment cores taken from Jaw lake (Bunger Hills, East Antarctica) were analysed for diatom composition and abundance. A diatom-salinity transfer function developed for the nearby Vestfold Hills was used to determine palaeosalinity reconstructions from the assemblages preserved in each of the cores. There is a large step-wise decrease in salinity in the second core from at least c. 4000 to c. 2000 uncorrected 14C yr BP. The salinity record from the first core starts at c. 3000 uncorrected 14C yr BP and is comparable with the salinity of the second core between c. 3000 and c. 2000 uncorrected 14C yr BP. Sudden lake water dilution in both cores at c. 1900 uncorrected 14C yr BP is followed by brief increases in lake water salinity between c. 1900 and c. 500 uncorrected 14C yr BP, after which gradual dilution to present occurs. This analysis of the local environmental history of this saline lake reveals a mid–late Holocene evolution of the lake basin similar to that documented from earlier marine and freshwater lacustrine sediments in the Bunger Hills. The high coherence of the independent sediment records suggests a robust general palaeosalinity reconstruction of the lake is achieved in addition to providing evidence for the fidelity of single sediment cores as useful and adequate representation of the palaeolimnological histories of Antarctic lakes.

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Holocene environmental changes in the Northern Khibiny mountains (Kola Peninsula) inferred by diatom analysis of lake sediments

Geomorphology RAS ◽

10.31857/s0435-42812019391-101 ◽

2019 ◽

pp. 91-101

Author(s):

O. S. Shilova ◽

F. A. Romanenko ◽

V. V. Kolka ◽

D. B. Denisov

Keyword(s):

Lake Sediments ◽

Kola Peninsula ◽

Environmental Changes ◽

Sediment Cores ◽

Lacustrine Sediments ◽

Early Holocene ◽

Diatom Analysis ◽

Weathering Processes ◽

Time Changes ◽

Evolution Of Vegetation

The article presents the results of diatom analysis of bottom sediment cores of Lake Shchuchye located in the northern part of the Khibiny Mountains. Data of radiocarbon dating of lacustrine sediments and comparison with previously published sections of lake sediments in the Kola Peninsula suggest that the accumulation of sediments in Shchuchye Lake began during the final stages of deglaciation in the early Holocene and continued uninterruptedly until the present time. Changes in the composition of diatom associations in sediments reflect alterations in the hydrodynamic regime of the lake associated with the isolation from the Goltsovoye Lake, influence of Kunyok River runoff, evolution of vegetation and weathering processes in the catchment area. We used concentration, variety and composition of species and distinguished 8 separate zones of diatoms. Climate changes in the Holocene are reflected directly in the change of the percentage of indicator species, and indirectly through changes in pH, etc. The early Holocene rise of temperature began in this region later than in the sea coastal area. It may reflect the pecularities of deglaciation, namely — late melting of alpine glaciers. Along with the evolutionary environmental changes some catastrophic events are reflected in the sediments of the Shchuchye Lake. For example, in early stages, there the yield of big quantity of terrigenous deposits into the lake was revealed produced by mud flows and erosion from slopes covered by scarce vegetation at that time. Mudflow processes probably led to the formation of a clear interlayer of terrigenous material in the biogenic sediments in the upper part of the section.

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Vegetation history of central Chukotka deduced from permafrost paleoenvironmental records of the El'gygytgyn Impact Crater

Climate of the Past ◽

10.5194/cp-8-1287-2012 ◽

2012 ◽

Vol 8 (4) ◽

pp. 1287-1300 ◽

Cited By ~ 26

Author(s):

A. A. Andreev ◽

E. Morozova ◽

G. Fedorov ◽

L. Schirrmeister ◽

A. A. Bobrov ◽

...

Keyword(s):

Impact Crater ◽

Environmental Changes ◽

Vegetation History ◽

Lacustrine Sediments ◽

Plant Macrofossils ◽

Early Holocene ◽

Shrub Tundra ◽

Dwarf Birch ◽

History Of ◽

Palynological Study

Abstract. Frozen sediments from three cores bored in the permafrost surrounding the El'gygytgyn Impact Crater Lake have been studied for pollen, non-pollen palynomorphs, plant macrofossils and rhizopods. The palynological study of these cores contributes to a higher resolution of time intervals presented in a poor temporal resolution in the lacustrine sediments; namely the Allerød and succeeding periods. Moreover, the permafrost records better reflect local environmental changes, allowing a more reliable reconstruction of the local paleoenvironments. The new data confirm that shrub tundra with dwarf birch, shrub alder and willow dominated the lake surroundings during the Allerød warming. Younger Dryas pollen assemblages reflect abrupt changes to grass-sedge-herb dominated environments reflecting significantly drier and cooler climate. Low shrub tundra with dwarf birch and willow dominate the lake vicinity at the onset of the Holocene. The find of larch seeds indicate its local presence around 11 000 cal yr BP and, thus a northward shift of treeline by about 100 km during the early Holocene thermal optimum. Forest tundra with larch and shrub alder stands grew in the area during the early Holocene. After ca. 3500 cal yr BP similar-to-modern plant communities became common in the lake vicinity.

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The postglacial diatom history of Sunfish Lake, southwestern Ontario

Canadian Journal of Botany ◽

10.1139/b73-204 ◽

1973 ◽

Vol 51 (9) ◽

pp. 1599-1609 ◽

Cited By ~ 15

Author(s):

M. R. Sreenivasa ◽

H. C. Duthie

Keyword(s):

Lacustrine Sediments ◽

Diatom Species ◽

Before Present ◽

Epiphytic Diatoms ◽

The Core ◽

Pollen Zone ◽

History Of ◽

Diatom Stratigraphy ◽

Number Of Individuals ◽

Stephanodiscus Hantzschii

An investigation was made of the diatom stratigraphy in a sediment core from Sunfish Lake, a small (8.3 ha), deep (20 m), meromictic lake in southwestern Ontario. About 340 diatom species and varieties distributed among 37 genera were identified from the sediments; however, only 16 taxa had more than 2% representation in any sample. On the whole, the number of individuals and diversity of the samples increase over the postglacial period. Diatoms first appear in pollen zone A and consist mainly of the littoral forms Cymbella diluviana, Fragilaria lapponica, and F. construens var. venter. It is suggested that these taxa are typical of early postglacial lacustrine sediments in northeastern North America. Cyclotella bodanica first appears in zone B and is dominant in most samples throughout the core. It is euplanktonic and typical of subalpine, circumneutral, oligotrophic lakes. In C2, when the climate was possibly warmer and drier than present, there is evidence for a lower lake level: C. bodanica is temporarily replaced in importance in the sediments by C. kuetzingiana and the proportion of littoral and epiphytic diatoms increases. Cyclotella bodanica regains its former importance in C3 sediments with the possible return to a cooler, wetter climate. About 850 years before present (B.P.) the lake evidently became eutrophic. Cyclotella bodanica declines and there is an increase in the proportion of several species typical of a higher trophic level, e.g., Stephanodiscus hantzschii, Cyclotella glomerata, and several Synedra spp. The cause is unknown. The lake probably became meromictic about 140 B.P. at a time when the forest was cleared and agriculture began in the watershed.

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An Assessment of Environmental Changes in Three Lakes from King's County (Nova Scotia, Canada) Using Diatom-Based Paleolimnological Techniques

Water Quality Research Journal ◽

10.2166/wqrj.2008.012 ◽

2008 ◽

Vol 43 (2-3) ◽

pp. 85-98 ◽

Cited By ~ 10

Author(s):

Joshua R. Thienpont ◽

Brian K. Ginn ◽

Brian F. Cumming ◽

John P. Smol

Keyword(s):

Nova Scotia ◽

Environmental Changes ◽

Sediment Cores ◽

Lake Management ◽

River System ◽

210Pb Dating ◽

Hydroelectric Power ◽

Diatom Assemblages ◽

Shoreline Development ◽

Before And After

Abstract Paleolimnological approaches using sedimentary diatom assemblages were used to assess water quality changes over the last approximately 200 years in three lakes from King's County, Nova Scotia. In particular, the role of recent shoreline development in accelerating eutrophication in these systems was assessed. Sediment cores collected from each lake were analyzed for their diatom assemblages at approximately 5-year intervals, as determined by 210Pb dating. Analyses showed that each system has changed, but tracked different ecosystem changes. Tupper and George lakes recorded shifts, which are likely primarily related to climatic warming, with diatom assemblages changing from a preindustrial dominance by Aulacoseira spp. to present-day dominance by Cyclotella stelligera. In addition to the recent climatic-related changes, further diatom changes in the Tupper Lake core between approximately 1820 and 1970 were coincident with watershed disturbances (farming, forestry, and construction of hydroelectric power infrastructure). Black River Lake has recorded an increase in diatom-inferred total phosphorus since about 1950, likely due to impoundment of the Black River system for hydroelectric generation and subsequent changes in land runoff. Before-and-after (i.e., top-bottom) sediment analyses of six other lakes from King's County provided further evidence that the region is being influenced by climatic change (decreases in Aulacoseira spp., increases in planktonic diatom taxa), as well as showing other environmental stressors (e.g., acidification). However, we recorded no marked increase in diatom-inferred nutrient levels coincident with shoreline cottage development in any of the nine study lakes. Paleolimnological studies such as these allow lake managers to place the current limnological conditions into a long-term context, and thereby provide important background data for effective lake management.

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Holocene polynya dynamics and their interaction with oceanic heat transport in northernmost Baffin Bay

Scientific Reports ◽

10.1038/s41598-021-88517-9 ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Rebecca Jackson ◽

Anna Bang Kvorning ◽

Audrey Limoges ◽

Eleanor Georgiadis ◽

Steffen M. Olsen ◽

...

Keyword(s):

Sediment Cores ◽

Active Role ◽

Atlantic Water ◽

The Arctic ◽

Negative Consequences ◽

Baffin Bay ◽

The North ◽

North Water ◽

History Of ◽

Ocean Conditions

AbstractBaffin Bay hosts the largest and most productive of the Arctic polynyas: the North Water (NOW). Despite its significance and active role in water mass formation, the history of the NOW beyond the observational era remains poorly known. We reconcile the previously unassessed relationship between long-term NOW dynamics and ocean conditions by applying a multiproxy approach to two marine sediment cores from the region that, together, span the Holocene. Declining influence of Atlantic Water in the NOW is coeval with regional records that indicate the inception of a strong and recurrent polynya from ~ 4400 yrs BP, in line with Neoglacial cooling. During warmer Holocene intervals such as the Roman Warm Period, a weaker NOW is evident, and its reduced capacity to influence bottom ocean conditions facilitated northward penetration of Atlantic Water. Future warming in the Arctic may have negative consequences for this vital biological oasis, with the potential knock-on effect of warm water penetration further north and intensified melt of the marine-terminating glaciers that flank the coast of northwest Greenland.

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