Characterising the Namaqualand Mudbelt: Chronology, Palynology and Palaeoenvironments

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dc.contributor.advisorMeadows, Michael Een_ZA
dc.contributor.advisorLee-Thorp, Julia Aen_ZA
dc.contributor.authorGray, Catherine Elizabeth Darnellen_ZA
dc.date.accessioned2014-07-31T08:04:47Z
dc.date.available2014-07-31T08:04:47Z
dc.date.issued2009en_ZA
dc.description.abstractThis multiproxy study explores the palaeoenvironmental record of two cores, H2 and H7, from the Namaqualand Mudbelt representing an arid and highly variable landscape. As bulk organic radiocarbon ages previously proved problematic, with anomalous reversals, the primary objective was to improve chronology and palaeoenvironmental reconstructions through high resolution 813C, 81SN and pollen analysis, with the aid of principal component analysis. Bulk organic radiocarbon dating of the surface sediment had previously yielded older than expected ages. New 210Pb analysis has established that these surface sediments are modem and radiocarbon ages are now recalibrated to yield an adjusted age of ±3 470 cal yr BP at the base of the more distal core, H7. Pollen spectra correlate well with stable isotopes and include recent disturbance indicators in the Succulent Karoo, Grassland, Karoo expansion, stock farming, impoundment, saltmarsh degradation and increase in domestic cereal cultivation. The proximal and distal mudbelt sites are, however, isotopically distinct, with 813C, inverse nitrogen and C/N ratios characterising H2 as more terrestrial. The excursion towards C3-rich values at around 6m depth in the proximal mudbelt suggests an increase in marine sources and C3 vegetation, while associated pollen aridity indicators implicate reduced inland flooding. This is contrasted against more humid conditions at 420 cm. Stronger upwelling occurred in near-surface distal mudbelt sediment and an influx of the Buffels River sediment flooded the region at ±3470 yr BP, indicating cooler, less arid conditions. 813C studies reveal the Lower Xobies palaeoflood deposit to be less C4-rich than expected, possibly due to sediment source, and is strikingly isotopically similar to the distal mudbelt. The palaeoenvironmental interpretation of the pollen assemblage, isotopes and chronology presents an improved understanding of the region represented in the mudbelt sediments. This corresponds well with established records of the last ±3 500 years and human induced land use change within the Orange River Catchment. Results also highlight the dynamics of the Orange River, which, combined with a highly variable climate, suggest that caution should be exercised to avoid over-interpreting the level at which environmental changes can meaningfully be reconstructed in arid landscapes, particularly those which are subject to sporadic and catastrophic flooding events.en_ZA
dc.identifier.apacitationGray, C. E. D. (2009). <i>Characterising the Namaqualand Mudbelt: Chronology, Palynology and Palaeoenvironments</i>. (Thesis). University of Cape Town ,Faculty of Science ,Department of Environmental and Geographical Science. Retrieved from http://hdl.handle.net/11427/4856en_ZA
dc.identifier.chicagocitationGray, Catherine Elizabeth Darnell. <i>"Characterising the Namaqualand Mudbelt: Chronology, Palynology and Palaeoenvironments."</i> Thesis., University of Cape Town ,Faculty of Science ,Department of Environmental and Geographical Science, 2009. http://hdl.handle.net/11427/4856en_ZA
dc.identifier.citationGray, C. 2009. Characterising the Namaqualand Mudbelt: Chronology, Palynology and Palaeoenvironments. University of Cape Town.en_ZA
dc.identifier.ris TY - Thesis / Dissertation AU - Gray, Catherine Elizabeth Darnell AB - This multiproxy study explores the palaeoenvironmental record of two cores, H2 and H7, from the Namaqualand Mudbelt representing an arid and highly variable landscape. As bulk organic radiocarbon ages previously proved problematic, with anomalous reversals, the primary objective was to improve chronology and palaeoenvironmental reconstructions through high resolution 813C, 81SN and pollen analysis, with the aid of principal component analysis. Bulk organic radiocarbon dating of the surface sediment had previously yielded older than expected ages. New 210Pb analysis has established that these surface sediments are modem and radiocarbon ages are now recalibrated to yield an adjusted age of ±3 470 cal yr BP at the base of the more distal core, H7. Pollen spectra correlate well with stable isotopes and include recent disturbance indicators in the Succulent Karoo, Grassland, Karoo expansion, stock farming, impoundment, saltmarsh degradation and increase in domestic cereal cultivation. The proximal and distal mudbelt sites are, however, isotopically distinct, with 813C, inverse nitrogen and C/N ratios characterising H2 as more terrestrial. The excursion towards C3-rich values at around 6m depth in the proximal mudbelt suggests an increase in marine sources and C3 vegetation, while associated pollen aridity indicators implicate reduced inland flooding. This is contrasted against more humid conditions at 420 cm. Stronger upwelling occurred in near-surface distal mudbelt sediment and an influx of the Buffels River sediment flooded the region at ±3470 yr BP, indicating cooler, less arid conditions. 813C studies reveal the Lower Xobies palaeoflood deposit to be less C4-rich than expected, possibly due to sediment source, and is strikingly isotopically similar to the distal mudbelt. The palaeoenvironmental interpretation of the pollen assemblage, isotopes and chronology presents an improved understanding of the region represented in the mudbelt sediments. This corresponds well with established records of the last ±3 500 years and human induced land use change within the Orange River Catchment. Results also highlight the dynamics of the Orange River, which, combined with a highly variable climate, suggest that caution should be exercised to avoid over-interpreting the level at which environmental changes can meaningfully be reconstructed in arid landscapes, particularly those which are subject to sporadic and catastrophic flooding events. DA - 2009 DB - OpenUCT DP - University of Cape Town LK - https://open.uct.ac.za PB - University of Cape Town PY - 2009 T1 - Characterising the Namaqualand Mudbelt: Chronology, Palynology and Palaeoenvironments TI - Characterising the Namaqualand Mudbelt: Chronology, Palynology and Palaeoenvironments UR - http://hdl.handle.net/11427/4856 ER - en_ZA
dc.identifier.urihttp://hdl.handle.net/11427/4856
dc.identifier.vancouvercitationGray CED. Characterising the Namaqualand Mudbelt: Chronology, Palynology and Palaeoenvironments. [Thesis]. University of Cape Town ,Faculty of Science ,Department of Environmental and Geographical Science, 2009 [cited yyyy month dd]. Available from: http://hdl.handle.net/11427/4856en_ZA
dc.language.isoeng
dc.publisher.departmentDepartment of Environmental and Geographical Scienceen_ZA
dc.publisher.facultyFaculty of Scienceen_ZA
dc.publisher.institutionUniversity of Cape Town
dc.subject.otherEnvironmental and Geographical Scienceen_ZA
dc.titleCharacterising the Namaqualand Mudbelt: Chronology, Palynology and Palaeoenvironmentsen_ZA
dc.typeDoctoral Thesis
dc.type.qualificationlevelDoctoral
dc.type.qualificationnamePhDen_ZA
uct.type.filetypeText
uct.type.publicationResearchen_ZA
uct.type.resourceThesisen_ZA
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