scholarly journals Last Interglacial Muir Point Formation, Vancouver Island, British Columbia

2007 ◽  
Vol 44 (3) ◽  
pp. 337-340 ◽  
Author(s):  
Stephen R. Hicock
Keyword(s):  
British Columbia ◽  
Alluvial Fan ◽  
Last Interglacial ◽  
Modern Pollen ◽  
Pollen Rain ◽  
Stratigraphic Position ◽  
Normal Polarity ◽  
Tidal Stream ◽  
Exposed Part ◽  
Study Sites

ABSTRACT The Muir Point Formation probably represents the last interglacial and climatic maximum of the Late Pleistocene in southwest British Columbia. It comprises estuarine, floodplain, fluvial, alluvial fan, and debris flow lithofacies. The lower exposed part of the formation is normally magnetized and probably formed during the Brunhes Normal Polarity Chron (<790 ka BP). On the basis of similar polarity, palynology, lithologies, and stratigraphic position, the Muir Point Formation is correlated with the Whidbey Formation of northwest Washington State. It probably also correlates with the Highbury Formation under the Fraser Lowland of mainland British Columbia.These formations may be remnants of shallow marine or subaerial sediment shelves which once rimmed ancestral Strait of Georgia and Puget basins over 100 ka, but were mostly removed by later glaciations. During this time sea level may have been 10 m higher than today. The middle floodplain unit contains five pollen zones whose differences can be explained mainly by shifts in a meandering tidal stream. Throughout most of this record Douglas fir pollen is more abundant than in modern pollen rain around the study sites which indicates that paleoclimate was at least as warm and dry as present.

The stratigraphy, palynology, and climatic significance of pre-middle Wisconsin Pleistocene sediments, southern Vancouver Island, British Columbia

1986 ◽  
Vol 23 (3) ◽  
pp. 369-382 ◽  
Author(s):  
Neville F. Alley ◽  
Stephen R. Hicock
Keyword(s):  
British Columbia ◽  
Vancouver Island ◽  
Fossil Pollen ◽  
Tree Line ◽  
Last Interglacial ◽  
Modern Pollen ◽  
Pollen Zone ◽  
Head Formation ◽  
Vegetation And Climate

Palynological investigations of organic-rich sediments from the Muir Point Formation and basal Cowichan Head Formation on southernmost Vancouver Island have identified seven pollen zones. Modern pollen spectra from the extant vegetation in southwestern British Columbia aid in interpreting paleoenvironments from the fossil pollen assemblages. Six of the pollen zones (MP-1, MP-2, MP-3, MP-4, CB-3, and CB-4) are from the Muir Point Formation and are beyond the range of 14C dating. They record evidence of vegetation and climate during either the last interglacial or penultimate interglacial (or some much older interglaciation) when conditions were at first warmer and (or) drier than at present, then succeeded to cooler and (or) moister conditions. The seventh and youngest pollen zone (MP-5) provides evidence of subalpine to near tree-line vegetation growing in cool–cold conditions before 43 000 years BP, during the early Olympia nonglacial interval. These pollen zones and interpretations are in part correlative with established zones from adjacent Washington and eastern Vancouver Island.

Vegetation and Climate of the Southern Chilean lake District During and Since the last Interglaciation

1974 ◽  
Vol 4 (3) ◽  
pp. 290-315 ◽  
Author(s):  
Calvin J. Heusser
Keyword(s):  
Beech Forest ◽  
Lake District ◽  
Modern Pollen ◽  
General Terms ◽  
Sphagnum Bogs ◽  
Pollen Rain ◽  
Southern Beech ◽  
Study Sites ◽  
Mass Circulation ◽  
Vegetation And Climate

The palynology of stratigraphic sections from road-cut and gravel-pit exposures and from a fen and sphagnum bogs in the southern part of the Chilean lake district (40° 53′ S, 72°37′ W-41°24′ S, 72°53′ W) is the basis for interpreting vegetation and climate during the last interglaciation and glaciation (named Llanquihue Glaciation) and during the post-glacial. To help interpretation, modern pollen rain was studied in relation to vegetation and altitude along a transect on the west slope of the Andes, and average January (summer) temperatures were interpreted. The upper limit of closed Andean forest, where wind is a determinant, appears to be close to the 12°C January isotherm; parkland in southern Chile does not exceed the January isotherm of 9°C.Grassland and later southern beech forest are evident during the interglaciation that is dated at more than 39,900 radiocarbon yr. Climate of the grassland was relatively dry; during the forest phase, it was wet, cool, and approximately the same as at present. During Llanquihue Glaciation, average January temperature is estimated to have been about 8°C colder than today at 19,450 BP, some 5° colder shortly before 36,300 BP, and around 4° colder at 10,000 BP. Antarctic-alpine tundra or parkland, under colder, drier climate, is mostly in evidence in the vicinity of the study sites before about 12,000 BP. During the postglacial, forest communities occupied the lake district, and temperatures there were probably 1–2°C above (by 6500 BP) and as much as 2° below (4500-0 BP) the present-day average of about 16°.This pattern of climatic changes finds accord, in general terms, in other parts of the Southern Hemisphere where palynological, chronological, and glacial geological studies are reported. Postulated as a cause of these changes are shifts in the intensity of air mass circulation in antarctic latitudes.

Pollen Taphonomy in a Canyon Stream

1987 ◽  
Vol 28 (3) ◽  
pp. 393-406 ◽  
Author(s):  
Patricia L. Fall
Keyword(s):  
Surface Soil ◽  
Pollen Grains ◽  
Close Correlation ◽  
Soil Samples ◽  
Alluvial Deposits ◽  
Modern Pollen ◽  
Pollen Types ◽  
Pollen Rain ◽  
Arid Steppe ◽  
Turbulent Water

AbstractSurface soil samples from the forested Chuska Mountains to the arid steppe of the Chinle Valley, Northeastern Arizona, show close correlation between modern pollen rain and vegetation. In contrast, modern alluvium is dominated by Pinus pollen throughout the canyon; it reflects neither the surrounding floodplain nor plateau vegetation. Pollen in surface soils is deposited by wind; pollen grains in alluvium are deposited by a stream as sedimentary particles. Clay-size particles correlate significantly with Pinus, Quercus, and Populus pollen. These pollen types settle, as clay does, in slack water. Chenopodiaceae-Amaranthus, Artemisia, other Tubuliflorae, and indeterminate pollen types correlate with sand-size particles, and are deposited by more turbulent water. Fluctuating pollen frequencies in alluvial deposits are related to sedimentology and do not reflect the local or regional vegetation where the sediments were deposited. Alluvial pollen is unreliable for reconstruction of paleoenvironments.

MODERN POLLEN RAIN STUDIES IN EASTERN ONTARIO

1963 ◽  
Vol 41 (2) ◽  
pp. 243-252 ◽  
Author(s):  
James E. King ◽  
Ronald O. Kapp
Keyword(s):  
United States ◽  
Long Range ◽  
Southwestern United States ◽  
Pollen Trap ◽  
Modern Pollen ◽  
Pollen Rain ◽  
Moss Polsters ◽  
Eastern Ontario

Moss polsters were collected at 15 sites between Toronto and Lake Timagami, Ontario, and at 4 localities in the Lake Timagami area for the purpose of determining the regional pollen rain and its local variations. Pollen percentages of Acer, Quercus, Ambrosia, Chenopodiaceae, Compositae, and Gramineae decrease northward and Picea, Pinus, and Betula increase at the more northerly sites. From the three most northern sites a regional pollen rain was calculated by averaging the percentages from nine pollen spectra. In this area the regional pollen rain is dominated by Picea (15%), Pinus (38%), and Betula (22%). At one site a grain of Ephedra was recovered, apparently carried in by long range drift. The nearest place that it grows naturally is in the southwestern United States. Various pollen trap types were investigated and it was found that all types of moss polsters and some types of decaying stumps (depending on their moisture-holding capacity) were effective in preserving the modern pollen rain.

Facies Composition and Stratigraphic Position of the Quaternary Upper Yenisei Sequence in the Tuva and Minusa Depressions

2021 ◽  
Vol 62 (10) ◽  
pp. 1127-1138
Author(s):  
I.D. Zol’nikov ◽  
I.S. Novikov ◽  
E.V. Deev ◽  
A.V. Shpansky ◽  
M.V. Mikharevich
Keyword(s):  
Late Pleistocene ◽  
Lacustrine Sediments ◽  
Alluvial Fan ◽  
Luminescence Dating ◽  
Middle Pleistocene ◽  
Mountainous Area ◽  
Gorny Altai ◽  
Stratigraphic Position ◽  
Geochronological Dating ◽  
Current Ripples

Abstract —The paper concerns the sediment sequence, which is widespread in the Yenisei valley and in the Tuva and Minusa depressions and also present in the valleys of the southern Chulym plain. The sediments of this sequence were previously described as “Neogene mud-shedding”, as well as moraines, alluvial fan deposits, alluvium of Middle Pleistocene high terraces, and lacustrine sediments. The giant ripple marks on the Upper Yenisei terraces was commonly interpreted as ribbed moraines; however, in recent studies, these ridges have been repeatedly referred to as marks of giant current ripples. Besides, some recently published papers provide description of geology of this sequence fragments suggesting its deposition by cataclysmic floods. Geomorphological analysis of the area shows Pleistocene glaciers to have been localized within the medium–high mountainous areas. The glaciers did not reach the Tuva and Minusa depressions and occupied large areas only in the Todzha basin and on the periphery of the Darkhat basin, forming a glacial dam at its outlet, which resulted in glacial-dammed lakes filling the basin completely. These lakes outburst, and the resultant flooding led to the deposition of megaflood sediments, which we refer to here as the Upper Yenisei sediment sequence. A detailed analysis of its facies architecture revealed similarity of these sediments to those of the Sal’dzhar and Inya sequences in Gorny Altai. Most of the Upper Yenisei megaflood sediments are localized in topographic lows of the Tuva and Minusa depressions. Beyond the Altai–Sayan mountainous area, the megaflood sediments of the Upper Yenisei sequence compose high terraces of the Yenisei, Chulym, Chet’, and Kiya rivers in the southern Chulym plain. The formation of Upper Yenisei sequence dates to the first half of the Late Pleistocene, inasmuch as it contains inset alluvial sediments of the second terrace of the Yenisei River. The available data allow suggesting that the Upper Yenisei sequence formed in the first Late Pleistocene regional glaciation. The Sal’dzhar sequence in Gorny Altai and the fourth terrace of the Ob’ River on the Fore-Altai plain are stratigraphic analogs of the Upper Yenisei sequence. The Upper Yenisei and Sal’dzhar sequences can thus be considered future regional markers serving as a link for the local stratigraphic schemes of the Altai–Sayan mountainous area and adjacent West Siberian plains. The results obtained call for verification by geochronological dating, first of all, by modern luminescence dating methods covering a wider chronological interval than radiocarbon dating.

scholarly journals Palaeomagnetic results from the Lopra-1/1A re-entry well, Faroe Islands

2006 ◽  
Vol 9 ◽  
pp. 51-65 ◽  
Author(s):  
Niels Abrahamsen
Keyword(s):  
Magnetic Susceptibility ◽  
Faroe Islands ◽  
Solid Core ◽  
Magnetic Remanence ◽  
Normal Polarity ◽  
Geophysical Logs ◽  
Exposed Part ◽  
Geomagnetic Polarity ◽  
Geomagnetic Polarity Time Scale ◽  
Made In

The palaeomagnetic dating and evolution of the Faroe Islands are discussed in the context of new density and rock magnetic results from the deepened Lopra-1/1A well. The reversal chronology of the c. 6½ km thick basalt succession is also described. The polarity record of the Faroe Islands may now be correlated in detail with the Geomagnetic Polarity Time Scale. The lowermost (hidden) part of the lower basalt formation correlates with Chron C26r (Selandian age), the top (exposed) part of the lower basalt formation correlates with Chrons C26n, C25r and C25n (Selandian and Thanetian age) and the middle and upper basalt formations correlate with Chron C24n.3r (Ypresian). Inclinations indicate a far-sided position of the palaeomagnetic poles, which is characteristic of results from most Palaeogene volcanics from the northern North Atlantic region. The density, magnetic susceptibility and magnetic remanence of 20 specimens from one solid core (1½ m in length) and 26 sidewall cores from the well between –2219 and –3531 m below sea level (b.s.l.) suggest that the volcanic materials can be divided into two characteristic groups: solid unaltered basalts and altered basalts and tuffs. The magnetic properties are typically log-normally distributed and the carriers of remanence are Ti-poor Ti-magnetites with Curie temperatures close to 580°C. The inclination of the 1½ m core at 2380 m b.s.l. is dominantly negative (two plugs at the very top of the core do show normal polarity, but they are likely to be misoriented as all specimens appear to be from one flow). Magnetic logging (magnetic susceptibility and field intensity) down to 3515 m b.s.l. was made in Lopra-1/1A together with other geophysical logs but did not yield conclusive inclination data.

scholarly journals Relación lluvia de polen-vetación en selvas de Quintana Roo

2017 ◽  
pp. 31 ◽  
Author(s):  
Gerald A. Islebe ◽  
Rogel Villanueva-Gutiérrez ◽  
Odilón Sánchez-Sánchez
Keyword(s):  
Zea Mays ◽  
Quintana Roo ◽  
Vegetation Types ◽  
Pollen Data ◽  
Indicator Taxa ◽  
Modern Pollen ◽  
Pollen Content ◽  
Ordination Techniques ◽  
Ordination Analysis ◽  
Pollen Rain

Modern pollen rain was studied along a 450 km long transect between Cancun-La Unión (Belizean border). Ten moss samples were collected in different vegetation types and analyzed for pollen content. The data were analyzed with classification (TWINSPAN), ordination analysis (DCA) and different association indices. Classification and ordination techniques allowed us to recognize three different pollen signals from semievergreen forest (with Maclura, Apocynaceae, Moraceae, Sapotaceae, Araceae, Cecropia, Celtis, Eugenia and Bursera), acahual (with con Coccoloba, Metopium, Anacardiaceae, Urticales, Melothria, Croton, Palmae) and disturbed vegetation (with Zea mays, Mimosa and Asteraceae ) . The degree of over-representation and underrepresentation of the pollen data with respect to the modem vegetation was established, being under-represented mostly entomophilous species. We can conclude that the actual pollen signal can be used for calibrating paleosignals, if clear groups of indicator taxa can be established.

Representativeness of tree diversity in the modern pollen rain of Andean montane forests

2013 ◽  
Vol 25 (2) ◽  
pp. 481-490 ◽  
Author(s):  
Nele Jantz ◽  
Jürgen Homeier ◽  
Hermann Behling
Keyword(s):  
Tree Diversity ◽  
Montane Forests ◽  
Modern Pollen ◽  
Pollen Rain

A new methodology for reconstructing climate and vegetation from modern pollen assemblages: an example from British Columbia

2009 ◽  
Vol 36 (4) ◽  
pp. 626-638 ◽  
Author(s):  
Simon Goring ◽  
Marlow G. Pellatt ◽  
Terri Lacourse ◽  
Ian R. Walker ◽  
Rolf W. Mathewes
Keyword(s):  
British Columbia ◽  
Modern Pollen ◽  
Modern Pollen Assemblages

scholarly journals Over 16,000 Years of Fire Frequency Determined from AMS Radiocarbon Dating of Soil Charcoal in an Alluvial Fan at Bear Flat, Northeastern British Columbia

Radiocarbon ◽  
2006 ◽  
Vol 48 (3) ◽  
pp. 435-450 ◽  
Author(s):  
A J Timothy Jull ◽  
Marten Geertsema
Keyword(s):  
British Columbia ◽  
Radiocarbon Dating ◽  
Large Scale ◽  
Fire Frequency ◽  
Alluvial Fan ◽  
Before Present ◽  
Ams Radiocarbon Dating ◽  
Soil Charcoal ◽  
Large Fires ◽  
Millennial Time Scale

We present results of radiocarbon dating of charcoal from paleosols and buried charcoal horizons in a unique sequence, which potentially records the last 36,000 yr, from a fan at Bear Flat, British Columbia (BC) (56°16'51’N, 121°13'39”W). Evidence for forest-fire charcoal is found over the last 13,500 ± 110 14C yr before present (BP) or 16,250 ± 700 cal BP. The study area is located east of the Rocky Mountains in an area that was ice-free at least 13,970 ± 170 14C yr BP (17,450–16,150 cal BP) ago. The latest evidence of fire is during the Medieval Warm Period (MWP). The charcoal ages show a periodicity in large fires on a millennial scale through the Holocene—an average of 4 fires per thousand years. Higher fire frequencies are observed between 2200 to 2800 cal BP, ∼5500 and ∼6000 cal BP, ∼7500 to 8200 cal BP, and 9000 to 10,000 cal BP. These intervals also appear to be times of above-average aggradation of the fan. We conclude that fire frequency is related to large-scale climatic events on a millennial time scale.

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