Palynology of late quaternary deposits from the central plateau, South Africa
| dc.contributor.advisor | Scott, Louis | |
| dc.contributor.author | Nyakale, Makisang | |
| dc.date.accessioned | 2018-05-11T06:44:15Z | |
| dc.date.available | 2018-05-11T06:44:15Z | |
| dc.date.issued | 1999-11 | |
| dc.description.abstract | English: Pollen analyses of organic sediments from Clarens, in the eastern Free State, Florisbad, in the central Free State and Blydefontein, in the Karoo were carried out to investigate the mechanism of vegetation and climatic changes in the South African interior during the Holocene. The methods of sampling, chemical processing and the construction of pollen diagrams and their zonation are described. In order to assist with the interpretation of past environmental changes, the relationship between physiography, the present climate and vegetation, is addressed. The nature of the different sites, their deposits and the radiocarbon dates obtained, are discussed. Furthemore, each sequence is described and interpreted in terms of past vegetation and climate changes. According to these reconstructions, the earliest phase recorded for the study area is for Florisbad, around 6500 to 6000 yr BP. This period was relatively dry and warm with high evaporation rates, as indicated by the presence of the local halophytic vegetation. The regional vegetation consisted of some grasses and Asteraceae shrubs and herbs. The period between 6000 and 5500 yr BP is not documented in any of the sequences, but it seems the drier phase continued throughout this time. Between 5400 and 5000 yr BP, conditions were sub-humid with dry episodes in Blydefontein, while Florisbad experienced dry conditions with reduced summer rains. The next phase between 4800 and 4000 yr BP is characterized by a complete change in the environmental conditions that include increased precipitation and a cooler climate in the interior. This is shown by the sequences from Blydefontein and Florisbad. The vegetation had a good grass cover with indications of cooling characteristic of the "Neoglacial' phase which occurred worldwide some time after 5000 yr BP. Seemingly, harsh conditions prevailed in the interior after ca. 4000 yr BP, as poor pollen preservation in sequences from Blydefontein and Florisbad indicate. The Blydefontein sediments show a very high percentage of trilete spores around 3950 yr BP, a possible sign of selective preservation, just below the barren part of the sequence. Although the Clarens sequence (Elim) dates havesome discrepancies, it also indicates a high percentage of trilete spores, especially for the period between 3000 and 4000 yr BP. The vegetation at Elim during this phase was open as a result of cool, dry conditions. The high percentage of trilete spores in Blydefontein and in Elim indicates poor pollen preservation that might be caused by the dessication of the sediments. All of the evidence for the period 3000-4000 yr BP points to dry conditions. The Florisbad sequence indicates the return of sub-humid conditions from ca. 3140 yr BP, while the Blydefontein sediments of this stage are still sterile. A decline in grasses accompanied by a rise in Chenopodiaceae/ Amaranthaceae pollen is seen in Florisbad ca. 2000 yr BP, possibly indicating a drier phase with increased evaporation. This situation was reversed around 1710 yr BP. Grassy vegetation appears at Blydefontein at ca. 1980 yr BP, suggesting a change to sub-humid conditions. The environmental changes since around 6500 yr BP to 1710 yr BP from Elim, Florisbad and Blydefontein agree with most of the available indications from the interior and with simulation models. Conditions in the interior only became sub-humid later during the Holocene altithermal, ca. 6500 yr BP, although the temperature was already high at this time. The period between 4000-2000 yr BP requires further research as most of the available sediments either have a hiatus or show an over-representation of trilete spores. This phase has been interpreted as indicative of harsh conditions for the preservation of pollen. | en_ZA |
| dc.description.abstract | Afrikaans: Stuifmeelanaliese van orgaruese sedimente van Clarens in die Oos-Vrystaat, Florisbad in die sentrale Vrystaat en Blydefontein in die Karoo, is uitgevoer om die meganisme van plantegroei- en klimaatsverandering in die binneland van Suid-Afrika, gedurende die Holoseen te ondersoek. Die metodes van monsterversameling, chemiese voorbereiding en die konstruksie van stuifrneeldiafrarnme en hulle sonering word beskryf. Om interpretasies van omgewingsveranderinge in die verlede te ondersteun is die verband tussen die fisiografie, die huidige klimaat en plantegroei ondersoek. Die aard van die verskillende studieplekke, die afsettings en radiokoolstof ouderdomspepalings daarvan word bespreek. Verder is elke opeenvolging beskryf en geïnterpreteer in terme van plantegroei- en klimaatsveranderinge in die verlede. Volgens hierdie rekonstruksies is die vroegste fase by Florisbad gevind teen ongeveer 6500 - 6000 jaar BP (voor hede). Hierdie periode was relatief droog en warm met 'n hoë verdampingstempo, soos aangedui deur die van lokale halofitiese plantegroei. Die regionale plantegroei het bestaan uit gras en Asteraceae-bossies en kruie. Die periode tussen 6000 en 5500 jaar BP is nie gedokumenteer in enige van die seksies nie, maar die droë fase het waarskynlik aangehou gedurende hierdie tyd. Tussen 5400 en 5000 jaar BP was toestande half-vogtig met droë episodes by Blydefontein, terwyl Florisbad droë toestande met minder somer-reën beleef het. Die volgende fase tussen 4800 en 4000 jaar BP is gekenmerk deur 'n groot verandering in omgewingstoestande wat verhoogde reënval en koeler toestande in die binneland behels. Dit word aangedui deur die opeenvolgings by Blydefontein en Florisbad. Die plantegroei was gekenmerk deur 'n goeie grassbedekking, met aanduidings dat dit relatif koel was soos gekenmerk deur die "neoglasiale" fase wat wêrelwyd net na 5000 jaar BP voorgekom het. Klaarblyklik het ongunstige toestande in die binneland na ongeveer 4000 jaar BP voorgekom soos aangedui deur swak stuifrneelpreservering.in die opeenvolgings van Blydefontein en Florisbad. In die Blydfontein-sedimente verskyn 'n relatiefhoë perserttasie van "trilete" spore, 'n aanduiding van selektiewe preservering, om en by teen 3950 jaar BP, net onder die onproduktiewe gedeelde van die opeenvolging. Al bestaan daar ongeruimthede in die datering van die Clarens-opeenvolging (Elim), dui dit ook 'n hoë pesentasie van "trilete" spore aan, veral in die tydperk tussen 3000 en 4000 jaar BP. Die plantegroei by Clarens (Elim) was oop as gevolg van koel, droë toestande. Die hoë persentasies van "trilete" spore in Blydefontein en Elim wys op swak stuifmeelpreservering wat moontlik deur die uitdroging van die sedimente veroorsaak is. Al die gegewens dui op droë toestande vir die periode 3000-4000 jaar BP. Die Florisbadopeenvolging dui aan dat half-vogtige toestande vannaf ca. 3140 jaar BP weer hulle verskyning gemaak het, terwyl die Blydefontein sedimente van hierdie tyd steriel IS. 'n Afname m grasse vergesel deur 'n toename m Chenopodiaceae/ Amaranthaceae-stuifmeel word waargeneem by Florisbad teen ca. 2000 jr BP, moontlik as aanduiding van 'n droër fase met meer verdamping, maar die situasie word omgekeer teen 1710 jaar BP. 'n Grasryke plantegroei verskyn by Blydefontein teen ca. 1980 jaar BP, wat half-vogtige toestande aandui. Die omgewingstoestande vanaf ca. 6500 jaar BP tot 1710 jaar BP by Elim, Florisbad en Blydefontein stem ooreen met meeste van die beskikbare indikasies uit die binneland en met simulasie-modelle. Toestande in die binneland gedurende die klimaatsoptimum van die Holoseen, het eers teen ca. 6500 jaar BP half- vogtig geword. Die periode tussen 4000 en 2000 jaar BP, moet verder nagevors word omdat meeste van die beskikbare sedimente of 'n leemte of oor-verteenwoordiging van "trilete" spore toon. Ongunstige toestande vir stuifmeelpreservering word gedurende hierdie tyd vermoed. | en_ZA |
| dc.description.sponsorship | FRD | en_ZA |
| dc.identifier.uri | http://hdl.handle.net/11660/8271 | |
| dc.language.iso | en | en_ZA |
| dc.publisher | University of the Free State | en_ZA |
| dc.rights.holder | University of the Free State | en_ZA |
| dc.subject | Palynology | en_ZA |
| dc.subject | Holocene deposits | en_ZA |
| dc.subject | Interior region | en_ZA |
| dc.subject | Vegetation | en_ZA |
| dc.subject | Palaeo-climatic trends | en_ZA |
| dc.subject | Neoglacial cooling | en_ZA |
| dc.subject | Holocene Altithermal | en_ZA |
| dc.subject | Palaeoenvironmental reconstruction | en_ZA |
| dc.subject | Evidence | en_ZA |
| dc.subject | Climate models and radiocarbon dating | en_ZA |
| dc.subject | Paleobotany -- Holocene | en_ZA |
| dc.subject | Dissertation (M.Sc. (Botany and Genetics))--University of the Free State, 1999 | en_ZA |
| dc.title | Palynology of late quaternary deposits from the central plateau, South Africa | en_ZA |
| dc.type | Dissertation | en_ZA |