Subsurface sediment profiles below Point Pelee: indicators of postglacial evolution in western Lake Erie

1998 ◽  
Vol 35 (1) ◽  
pp. 88-99
Author(s):  
John P Coakley ◽  
Allan S Crowe ◽  
Patrice A Huddart
Keyword(s):  
Lake Levels ◽  
Dune Sand ◽  
Radiocarbon Dates ◽  
Subsurface Sediment ◽  
Fine Grained ◽  
Western Lake ◽  
Planar Wave ◽  
Point Pelee ◽  
Sediment Data ◽  
Point Pelee National Park

An extensive drilling program, undertaken along the western barrier bar at Point Pelee National Park, Ontario, Canada, yielded considerable subsurface sediment data relevant to the nature and lateral geometry of sedimentary units below the Point Pelee foreland. Four major sedimentary units were identified: a basal clay-rich till, a fine-grained glaciolacustrine sand, a medium-grained sand unit (subdivided into a poorly sorted shoreface sand and an aeolian (dune) sand derived from the shoreface sand), and an organic marsh (gyttja) deposit. The present study confirms the existence of a planar, wave-eroded till surface below the southern portion of Point Pelee at an elevation of approximately 164 m asl. Following this low-water period in the basin, lake levels rose abruptly to an elevation several metres above 172 m asl. This resulted in erosion of the upper part of the glaciolacustrine sand during a later period of stable higher lake levels, perhaps coinciding with the Nipissing flood event (about 4000 BP). This resulted in a planar surface at approximately 169.5 m asl. Several radiocarbon dates on basal gyttja from the marsh (averaging 3200 BP) reflect a subsequent drop in levels to about 2-3 m below present levels. Though undated, the initiation of shoreface and dune sand deposition is roughly coeval with the basal marsh deposits.

The formation and evolution of Point Pelee, western Lake Erie

1976 ◽  
Vol 13 (1) ◽  
pp. 136-144 ◽  
Author(s):  
J. P. Coakley
Keyword(s):  
Lake Erie ◽  
Present Position ◽  
Lake Levels ◽  
Western Basin ◽  
Beach Ridges ◽  
Western Lake ◽  
Formation And Evolution ◽  
Position And Orientation ◽  
Point Pelee ◽  
Western Lake Erie

Point Pelee originated as a sandy foreland enclosing a marsh approximately 4000 years BP. A reconstruction of paleoenvironmental conditions prior to that time suggests strongly that it was formed initially by the progressive merging of beach ridges and dunes formed on opposite sides of the Pelee-Lorain moraine when rising lake levels in the western basin of Lake Erie were 3 to 4 m below present lake datum (173.4 m above sea level). Since that time, it has retreated to its present position and orientation under the influence of slowly rising lake levels and increasing wave energy from both sides.Such an evolution, though different from conventional mechanisms of spit formation, is supported by evidence derived from the local post glacial stratigraphy and the geomorphology of relict features preserved on the Point and on the shoal area to the south.

The Hayes Tephra Deposits, and Upper Holocene Marker Horizon in South-Central Alaska

1990 ◽  
Vol 33 (3) ◽  
pp. 276-290 ◽  
Author(s):  
James R. Riehle ◽  
Peter M. Bowers ◽  
Thomas A. Ager
Keyword(s):  
Cook Inlet ◽  
Radiocarbon Dates ◽  
Fine Grained ◽  
South Central ◽  
Inlet Region ◽  
Tephra Deposits ◽  
Phenocryst Content

AbstractThe most widespread of all Holocene tephra deposits in the Cook Inlet region of south-central Alaska is a set of deposits from Hayes volcano. Because of their unique phenocryst content—biotite in rare amounts and a high proportion of amphibole to pyroxene—the deposits are readily identifiable at all but the most distant sites where they are very fine grained. Eighteen radiocarbon dates from eight upland sites limit the age of the tephra set to between about 3500 and 3800 yr. The set originated at Hayes volcano in the Tordrillo Mountains 150 km northwest of Anchorage; seven or possibly eight closely succeeding deposits, low-silica dacite in composition, compose two main lobes that extend northeast for 400 km and south for at least 250 km from the vent. We estimate the total tephra volume to be 10 km3; multiple layers imply four to six larger and two or three smaller eruptions. The deposits are a nearly isochronous marker horizon that should be useful in future archeologic, geologic, and palynologic studies in the region.

scholarly journals Ice-rafting in lakes in the early Neoproterozoic: dropstones in the Diabaig Formation, Torridon Group, NW Scotland

2019 ◽  
Vol 56 (1) ◽  
pp. 47-53
Author(s):  
Adrian Hartley ◽  
Bartosz Kurjanski ◽  
Jessica Pugsley ◽  
Joseph Armstrong
Keyword(s):  
Lake Levels ◽  
Fine Grained ◽  
Lateral Distance ◽  
Ice Rafting ◽  
Lake Deposits ◽  
Early Neoproterozoic

A dropstone horizon is described from lake deposits in a palaeo-valley from the c. 1000 Ma Diabaig Formation, Torridon Group, NW Scotland. Dropstones occur in wave-rippled, fine-grained sandstones and siltstones that contain desiccation and syneresis cracks indicative of fluctuating lake levels. Five locally derived dropstones occur at the same horizon over lateral distance of 250 m and display clear evidence of deflection and penetration of laminae at the base, with thinning, onlap and draping of laminae on to clast margins and tops. Mechanisms of dropstone formation are discussed, with ice-rafting considered the most likely explanation. It is suggested that rafting was promoted by cold winters at 35° S in the early Neoproterozoic, possibly in an upland setting. Interpretation of the dropstones as ice-rafted debris provides the first physical record of evidence for ice at the Earth's surface during the late Mesoproterozoic to early Neoproterozoic.

The Folsom (Paleoindian) Type Site: Past Investigations, Current Studies

2002 ◽  
Vol 67 (1) ◽  
pp. 5-36 ◽  
Author(s):  
David J. Meltzer ◽  
Lawrence C. Todd ◽  
Vance T. Holliday
Keyword(s):  
Faunal Remains ◽  
Radiocarbon Dates ◽  
Projectile Points ◽  
Fine Grained ◽  
Lithic Assemblage ◽  
Wild Horse ◽  
Field Investigations ◽  
Type Site ◽  
High Utility ◽  
Cultural Origins

Research on the Folsom Paleoindian type site, involving renewed field investigations and an analysis of extant collections from the 1920s excavations, was undertaken between 1997 and 2000. The preliminary results of that research show that all excavations to date have been in the kill area, which took place in a small and relatively shallow tributary to the Pleistocene paleovalley of Wild Horse Arroyo as well as in the paleovalley itself. Preliminary butchering of ∼32 Bison antiquus took place near where the animals were dropped. The kill area is dominated by low-utility bone elements and broken projectile points; high-utility bones and tools for processing meat and hides are rare or absent, and either occur in another, as-yet undiscovered area of the site, or altogether off-site. Faunal remains are generally in excellent condition. Those in the tributary are mostly in primary context, and underwent rapid burial beneath fine-grained (dominantly aeolian) sediments, which in turn were subsequently armored by a shingle shale; those in the paleovalley experienced postdepositional transport and redeposition. The small lithic assemblage is dominated by projectile points and comprised of material mostly from two sources in the Texas panhandle, several hundred kilometers southeast of the site. It also includes stone obtained from sources at comparable distances north and northwest of the site. A series of radiocarbon ages is available for the stratigraphic units, nearly all from charcoal of non-cultural origins; radiocarbon dates on bison bone put the age of the kill at 10,500 B.P.

Pieces in vertical movement—a model for rockshelter archaeology

1977 ◽  
Vol 43 ◽  
pp. 349-353 ◽  
Author(s):  
Ari Siiriäinen
Keyword(s):  
Vertical Movement ◽  
Stone Age ◽  
Radiocarbon Dates ◽  
Fine Grained ◽  
Late Stone Age ◽  
Vertical Scale ◽  
Small Stone ◽  
Image Position

In 1973, excavations were carried out in a rockshelter called River Rockshelter in Laikipia District, Kenya (the results will be published in AZANIA). The archaeological deposit was c 80 cm thick and contained an abundant lithic material belonging to a Late Stone Age industry. The deposit was excavated in seven layers each 5–15 cm thick. The stratigraphy was as follows (fig. 1):1. 0–10 cm, brown, loose fine-grained earth;2. 10–35 cm, brown, hard, medium-grained soil with stone slabs;3. 35–50 cm, greyish brown, hard gravel with small stone slabs;4. 50 cm + grey, hard gravel.Stratigraphical layers, radiocarbon dates and excavated layers from River Rockshelter. Vertical scale 1/10.

Pollen Diagram from the Nebraska Sandhills and the Age of the Dunes

1985 ◽  
Vol 24 (1) ◽  
pp. 115-120 ◽  
Author(s):  
H. E. Wright ◽  
J. C. Almendinger ◽  
J. Grüger
Keyword(s):  
Sand Dunes ◽  
Dune Sand ◽  
Last Glacial Period ◽  
Pollen Diagram ◽  
Radiocarbon Dates ◽  
The Holocene ◽  
Swan Lake ◽  
Nebraska Sandhills ◽  
Prairie Vegetation ◽  
The Last Glacial

Radiocarbon dates of organic alluvium beneath as much as 40 m of dune sand along the Dismal River have led to the suggestion that the Nebraska Sandhills date from the Holocene rather than the last glacial period. On the other hand, the basal layers of lake and marsh deposits in interdune depressions at three localities date in the range of 9000 to 12,000 yr B.P., implying a pre-Holocene age for the sand dunes. A pollen diagram for one of these sites, Swan Lake, indicates prairie vegetation throughout the last 9000 yr, with no suggestion that the landscape was barren enough to permit the shaping of the massive dunes characterizing the area. Sand was not transported across the site during the Holocene, either during the marsh phase, which lasted until 3700 yr B.P., or during the subsequent lake phase. The sand that buries the alluvium along the Dismal River may represent only local eolian activity, or it may indicate that the younger of the two main dune series identified by H. T. U. Smith (1965, Journal of Geology 73, 557–578) is Holocene in age, and the older one Late Wisconsin in age.

Spatial distribution and microhabitat use in the five-lined skink (Eumeces fasciatus)

1993 ◽  
Vol 71 (3) ◽  
pp. 445-450 ◽  
Author(s):  
Carolyn N. L. Seburn
Keyword(s):  
Spatial Distribution ◽  
Surface Area ◽  
Microhabitat Use ◽  
Male Adult ◽  
Nest Sites ◽  
Males And Females ◽  
Point Pelee ◽  
Cover Thickness ◽  
Point Pelee National Park ◽  
Reduced Activity

Patterns of spatial distribution and microhabitat use in Eumeces fasciatus were examined in a population at Point Pelee National Park, Canada. Each individual was uniquely marked and classified as adult male, adult female, yearling, or hatchling. In each census the location of individuals was recorded. At each microsite, I measured thickness and surface area of cover, degree of shading, and distance to nearest neighbouring microsite.Significant aggregation was found among individuals within age and sex classes. Males and females associated significantly during the breeding season but not at other times. The number of captures made at a microsite was positively correlated with cover surface area and negatively correlated with cover thickness. Nest sites were the most used subset of all sites at which individuals were captured. Evidence was found to suggest that some females shift home range, once prior to oviposition, and again after hatching of eggs. Males demonstrated reduced activity after oviposition and may aestivate.

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