A Late Quaternary Pollen Record from the Transvaal Bushveld, South Africa

1982 ◽  
Vol 17 (3) ◽  
pp. 339-370 ◽  
Author(s):  
Louis Scott
Keyword(s):  
South Africa ◽  
Late Quaternary ◽  
Montane Forest ◽  
Fossil Pollen ◽  
Pollen Record ◽  
Vegetation Types ◽  
Northern Plains ◽  
Pollen Data ◽  
The Past ◽  
Climatic Evolution

AbstractPollen spectra from cores of organic spring deposits from the Transvaal provide evidence for the climatic evolution of the province during the last 35,000 yr B.P. or more. The past climatic phases are derived from palynological reconstructions of past vegetation types by comparison of fossil pollen data with modern surface pollen spectra from various localities. Evidence is provided for an early moist, cool phase with relatively mesic bushveld and expanded montane forest in the central Transvaal, followed by a drier period with drier bushveld which probably lasted until approximately 25,000 yr B.P. During the next phase, which at the latest ended about 11,000 yr B.P., the temperatures were probably 5°–6°C cooler than at present. At that time bushveld vegetation in the central Transvaal was replaced by open grassland with macchia elements. Climatic amelioration came and semiarid savanna returned to the plains, at first gradually and then developing into a warm Kalahari thornveld-type vegetation. After 6000 yr B.P. it apparently became slightly wetter and a more broad-leafed bushveld developed. About 4000 yr B.P. it again became cooler and slightly wetter and the bushveld vegetation on the central and northern plains was comparable to present open upland types. After 2000 yr B.P. conditions gradually became warner until about 1000 yr B.P., when the modern climate of the central Transvaal bushveld originated.

Late Quaternary Paleotemperatures Derived from a Speleothem from Cango Caves, Cape Province, South Africa

1992 ◽  
Vol 37 (2) ◽  
pp. 203-213 ◽  
Author(s):  
A.S. Talma ◽  
John C. Vogel
Keyword(s):  
South Africa ◽  
Isotopic Composition ◽  
Late Quaternary ◽  
Carbon Isotopic Composition ◽  
Temperature Record ◽  
The Past ◽  
Carbon Isotopic ◽  
Groundwater Aquifer ◽  
Combining Data ◽  
The Last Glacial

AbstractAn oxygen isotope temperature record over a large part of the past 30,000 yr has been obtained for the southern Cape Province of South Africa by combining data on the isotopic composition of a stalagmite from a deep cave with that of a confined groundwater aquifer in the same region. Results show that temperatures during the last glacial maximum were on average about 6°C lower than those today, with peaks up to 7°C lower. A detailed analysis of the past 5000 yr suggests multiple fluctuations, with generally lower temperatures (1–2°C) around 4500 and 3000 yr B.P. The carbon isotopic composition of the stalagmite indicates significant vegetation changes between the late Pleistocene and today, and also during the second half of the Holocene.

scholarly journals Late Quaternary climate variability at Mfabeni peatland, eastern South Africa

2019 ◽  
Vol 15 (3) ◽  
pp. 1153-1170 ◽  
Author(s):  
Charlotte Miller ◽  
Jemma Finch ◽  
Trevor Hill ◽  
Francien Peterse ◽  
Marc Humphries ◽  
...  
Keyword(s):  
South Africa ◽  
High Pressure ◽  
Indian Ocean ◽  
Late Quaternary ◽  
High Pressure Cell ◽  
Sea Ice Extent ◽  
Pressure Cell ◽  
The Past ◽  
Antarctic Sea Ice ◽  
Quaternary Climate

Abstract. The scarcity of continuous, terrestrial, palaeoenvironmental records in eastern South Africa leaves the evolution of late Quaternary climate and its driving mechanisms uncertain. Here we use a ∼7 m long core from Mfabeni peatland (KwaZulu-Natal, South Africa) to reconstruct climate variability for the last 32 000 years (cal ka BP). We infer past vegetation and hydrological variability using stable carbon (δ13Cwax) and hydrogen isotopes (δDwax) of plant-wax n-alkanes and use Paq to reconstruct water table changes. Our results indicate that late Quaternary climate in eastern South Africa did not respond directly to orbital forcing or to changes in sea-surface temperatures (SSTs) in the western Indian Ocean. We attribute the arid conditions evidenced at Mfabeni during the Last Glacial Maximum (LGM) to low SSTs and an equatorward displacement of (i) the Southern Hemisphere westerlies, (ii) the subtropical high-pressure cell, and (iii) the South Indian Ocean Convergence Zone (SIOCZ), which we infer was linked to increased Antarctic sea-ice extent. The northerly location of the high-pressure cell and the SIOCZ inhibited moisture advection inland and pushed the rain-bearing cloud band north of Mfabeni, respectively. The increased humidity at Mfabeni between 19 and 14 cal kyr BP likely resulted from a southward retreat of the westerlies, the high-pressure cell, and the SIOCZ, consistent with a decrease in Antarctic sea-ice extent. Between 14 and 5 cal kyr BP, when the westerlies, the high-pressure cell, and the SIOCZ were in their southernmost position, local insolation became the dominant control, leading to stronger atmospheric convection and an enhanced tropical easterly monsoon. Generally drier conditions persisted during the past ca. 5 cal ka BP, probably resulting from an equatorward return of the westerlies, the high-pressure cell, and the SIOCZ. Higher SSTs and heightened El Niño–Southern Oscillation (ENSO) activity may have played a role in enhancing climatic variability during the past ca. 5 cal ka BP. Our findings highlight the influence of the latitudinal position of the westerlies, the high-pressure cell, and the SIOCZ in driving climatological and environmental changes in eastern South Africa.

Tsunami on Mars: Implications for the duration and timing of a northern ocean

2020 ◽  
Author(s):  
Francois Costard ◽  
José Alexis Palmero Rodriguez ◽  
Antoine Séjourné ◽  
Anthony Lagain ◽  
Steve Clifford ◽  
...  
Keyword(s):  
Climate Models ◽  
Northern Plains ◽  
The Past ◽  
Time Period ◽  
Total Inventory ◽  
Climatic Evolution ◽  
Global Inventory ◽  
The Impact ◽  
Equivalent Layer ◽  
Potential Origin

<p>The duration and timing of a northern ocean is a key issue in understanding the past geological and climatic evolution of Mars. Mars experienced its greatest loss of H<sub>2</sub>O between the Noachian and Late Hesperian (~10 m Global Equivalent Layer, Jakosky et al., 2017) roughly the same amount that is thought to have been added to the global inventory by extrusive volcanism over the same time period (Carr and Head, 2015). Thus, the total inventory of water was probably similar during these two epochs. But, the ocean during the Late Hesperian was smaller in extension than the ocean during the Noachian– with significant implications for the potential origin and survival of life. Here we examine the implications of the existence of a Late Hesperian/ Early Amazonian ocean on the planet’s inventory of water (and especially liquid water) and its variation with time. Our previous work (Rodriguez et al., 2016; Costard et al., 2017) concluded that the most plausible explanation for the origin of the Thumbprint Terrain (TT) lobate deposits, with run-ups, found along the dichotomy boundary, especially in Arabia Terra, was tsunami deposits. This supports the hypothesis that an ocean occupied the northern plains of Mars as recently as ~3 billion years ago. Furthermore, Costard et al (2017) produced a tsunami numerical model showing that the TT deposits exhibit fine-scale textural patterns due to the wave’s interference patterns resulting from interactions with the coastal topography. More recently, we suggested that the unusual characteristics of Lomonosov crater (50.52°N/16.39°E ) in the northern plains are best explained by the presence of a shallow ocean at the time of the impact (Costard et al., 2019). Interestingly, the apparent agreement between the age of the Lomonosov impact and that of the TT unit (~3 Ga), strongly suggests that it was the source of the tsunami (Costard et al., 2019). Our preliminary assessment indicates that this impact-generated tsunami required a mostly liquid ocean and because of the high latitude location of the Lomonosov crater site, our results strongly imply relatively warm paleoclimatic conditions. Our conclusions highlight the need for more sophisticated climate models.</p>

Late Quaternary History of Tundra Vegetation in Northwestern Alaska

1994 ◽  
Vol 41 (3) ◽  
pp. 306-315 ◽  
Author(s):  
Patricia M. Anderson ◽  
Patrick J. Bartlein ◽  
Linda B. Brubaker
Keyword(s):  
Vegetation Type ◽  
Late Quaternary ◽  
Vegetation Types ◽  
The Past ◽  
Modern Pollen ◽  
Qualitative Approaches ◽  
Tundra Vegetation ◽  
Shrub Tundra ◽  
History Of ◽  
Quaternary History

AbstractPollen analysis of a new core from Joe Lake indicates that the late Quaternary vegetation of northwestern Alaska was characterized by four tundra and two forest-tundra types. These vegetation types were differentiated by combining quantitative comparisons of fossil and modern pollen assemblages with traditional, qualitative approaches for inferring past vegetation, such as the use of indicator species. Although imprecisely dated, the core probably spans at least the past 40,000 yr. A graminoid-Salix tundra dominated during the later and early portions of the glacial record. The middle glacial interval and the transition from glacial to interglacial conditions are characterized by a graminoid-Betula-Salix tundra. A Populus forest-Betula shrub tundra existed during the middle potion of this transition, being replaced in the early Holocene by a Betula-Alnus shrub tundra. The modern Picea forest-shrub tundra was established by the middle Holocene. These results suggest that the composition of modem tundra communities in northwestern Alaska developed relatively recently and that throughout much of the late Quaternary, tundra communities were unlike the predominant types found today in northern North America. Although descriptions of vegetation variations within the tundra will always be restricted by the innate taxonomic limitations of their herb-dominated pollen spectra, the application of multiple interpretive approaches improves the ability to reconstruct the historical development of this vegetation type.

Late Quaternary vegetation and environments in the Verkhoyansk Mountains region (NE Asia) reconstructed from a 50-kyr fossil pollen record from Lake Billyakh

2010 ◽  
Vol 29 (17-18) ◽  
pp. 2071-2086 ◽  
Author(s):  
Stefanie Müller ◽  
Pavel E. Tarasov ◽  
Andrei A. Andreev ◽  
Thomas Tütken ◽  
Steffi Gartz ◽  
...  
Keyword(s):  
Late Quaternary ◽  
Fossil Pollen ◽  
Pollen Record

scholarly journals Thresholds of potential concern as benchmarks in the management of African savannahs

2007 ◽  
Vol 362 (1478) ◽  
pp. 309-319 ◽  
Author(s):  
L Gillson ◽  
K.I Duffin
Keyword(s):  
Vegetation Cover ◽  
Vegetation Change ◽  
Quadratic Equation ◽  
Woody Vegetation ◽  
Fossil Pollen ◽  
Pollen Record ◽  
Pollen Data ◽  
Modern Pollen ◽  
Management Objectives ◽  
Arboreal Pollen

In the Kruger National Park (KNP), South Africa, ecosystem managers use a series of monitoring endpoints, known as thresholds of potential concern (TPCs), to define the upper and the lower levels of accepted variation in ecosystems. For woody vegetation, the current TPC suggests that woody cover should not drop by more than 80% of its ‘highest ever’ value. In this paper, we explore the utility of palaeoecological data in informing TPCs. We use calibrated fossil pollen data to explore variability in vegetation at two sites over the past 5000 years, to provide a long-term record of changes in woody vegetation cover and a context for interpreting more recent vegetation change. The fossil pollen data are calibrated using studies of modern pollen and vegetation from KNP; arboreal pollen percentage was simulated using pollen–landscape modelling software for savannah landscapes of varying woody vegetation cover, and the relationship between vegetation and pollen data was quantified using nonlinear regression. This quadratic equation was then applied to fossil pollen data in order to estimate woody vegetation cover from arboreal pollen percentages. Our results suggest that the TPCs have not been exceeded during the period represented in the pollen record, because estimated woody vegetation cover has remained above 20% of its highest ever value. By comparing the fossil pollen data with TPCs, our study demonstrates how palaeoecological data can be presented in a form that is directly relevant to management objectives.

scholarly journals A gap analysis of ornithological research in the brazilian state of Roraima

2012 ◽  
Vol 12 (2) ◽  
pp. 71-81
Author(s):  
Marcos Pérsio Dantas Santos
Keyword(s):  
National Park ◽  
Gap Analysis ◽  
Bird Species ◽  
Montane Forest ◽  
Vegetation Types ◽  
Avian Diversity ◽  
Terra Firme ◽  
The Past ◽  
Brazilian State ◽  
The Town

This study analyzes the ornithological data available for the Brazilian state of Roraima, focusing on sampling gaps. All ornithological data collected in Roraima up to the present were collated with the aim of answering the following questions: (a) which sites have been well sampled? (b) Are there are any geographic gaps? (c) What is the current extent of the scientific knowledge of avian diversity in Roraima? (d); Which regions and vegetation types have been well-sampled, and which should be prioritized for future surveys? Ornithological data were obtained from a total of 82 localities, including the Maracá Ecological Station (442 species), Viruá National Park (420 species), Colônia do Apiaú (320 species), Mucajaí (267 species), and Pacaráima (212 species), which were the five sites with the highest species counts. Over the past 20 years, only two localities in Roraima have been added to the list of sites with reliable samples (at least 100 bird species recorded (study skins collected, tape recordings and undocumented field observations) , the Viruá National Park and Fazenda Paraense. Five regions of the state were identified as sampling gaps, and should be prioritized in future ornithological surveys: the northwest, on the border with Venezuela and the Brazilian state of Amazonas, the lower Rio Branco between the town of Caracaraí and the mouth of the river, the terra firme forests of the southeast, the savannas of the northeast, on the border with Guyana, and the northern highlands, including montane forest and tepuis.

scholarly journals Glacial-interglacial vegetation dynamics in South Eastern Africa coupled to sea surface temperature variations in the Western Indian Ocean

2011 ◽  
Vol 7 (4) ◽  
pp. 1209-1224 ◽  
Author(s):  
L. M. Dupont ◽  
T. Caley ◽  
J.-H. Kim ◽  
I. Castañeda ◽  
B. Malaizé ◽  
...  
Keyword(s):  
South Africa ◽  
Indian Ocean ◽  
Surface Temperature ◽  
Sea Surface Temperature ◽  
River Mouth ◽  
Sea Surface ◽  
Eastern Africa ◽  
Temperature Record ◽  
Pollen Record ◽  
The Past

Abstract. Glacial-interglacial fluctuations in the vegetation of South Africa might elucidate the climate system at the edge of the tropics between the Indian and Atlantic Oceans. However, vegetation records covering a full glacial cycle have only been published from the eastern South Atlantic. We present a pollen record of the marine core MD96-2048 retrieved by the Marion Dufresne from the Indian Ocean ∼120 km south of the Limpopo River mouth. The sedimentation at the site is slow and continuous. The upper 6 m (spanning the past 342 Ka) have been analysed for pollen and spores at millennial resolution. The terrestrial pollen assemblages indicate that during interglacials, the vegetation of eastern South Africa and southern Mozambique largely consisted of evergreen and deciduous forests. During glacials open mountainous scrubland dominated. Montane forest with Podocarpus extended during humid periods was favoured by strong local insolation. Correlation with the sea surface temperature record of the same core indicates that the extension of mountainous scrubland primarily depends on sea surface temperatures of the Agulhas Current. Our record corroborates terrestrial evidence of the extension of open mountainous scrubland (including fynbos-like species of the high-altitude Grassland biome) for the last glacial as well as for other glacial periods of the past 300 Ka.

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