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Characterising the Namaqualand Mudbelt: Chronology, Palynology and Palaeoenvironments
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 chron...
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| Format: | Thesis |
| Language: | English |
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Department of Environmental and Geographical Science
2014
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| _version_ | 1867613264682156032 |
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| access_status_str | Open Access |
| author | Gray, Catherine Elizabeth Darnell |
| author2 | Meadows, Michael E |
| author_browse | Gray, Catherine Elizabeth Darnell Meadows, Michael E |
| author_facet | Meadows, Michael E Gray, Catherine Elizabeth Darnell |
| author_sort | Gray, Catherine Elizabeth Darnell |
| collection | Thesis |
| description | 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. |
| format | Thesis |
| id | oai:open.uct.ac.za:11427/4856 |
| institution | University of Cape Town (South Africa) |
| language | eng |
| last_indexed | 2026-06-10T12:33:23.204Z |
| license_str | Not specified — see source repository |
| provenance_str_mv | Harvested via OAI-PMH from UCTD — University of Cape Town Open Access Repository |
| publishDate | 2014 |
| publishDateRange | 2014 |
| publishDateSort | 2014 |
| publisher | Department of Environmental and Geographical Science |
| publisherStr | Department of Environmental and Geographical Science |
| record_format | dspace |
| source_str | UCTD — University of Cape Town Open Access Repository |
| spelling | oai:open.uct.ac.za:11427/4856 Characterising the Namaqualand Mudbelt: Chronology, Palynology and Palaeoenvironments Gray, Catherine Elizabeth Darnell Meadows, Michael E Lee-Thorp, Julia A Environmental and Geographical Science 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. 2014-07-31T08:04:47Z 2014-07-31T08:04:47Z 2009 Doctoral Thesis Doctoral PhD http://hdl.handle.net/11427/4856 eng application/pdf Department of Environmental and Geographical Science Faculty of Science University of Cape Town |
| spellingShingle | Environmental and Geographical Science Gray, Catherine Elizabeth Darnell Characterising the Namaqualand Mudbelt: Chronology, Palynology and Palaeoenvironments |
| thesis_degree_str | Doctoral |
| title | Characterising the Namaqualand Mudbelt: Chronology, Palynology and Palaeoenvironments |
| title_full | Characterising the Namaqualand Mudbelt: Chronology, Palynology and Palaeoenvironments |
| title_fullStr | Characterising the Namaqualand Mudbelt: Chronology, Palynology and Palaeoenvironments |
| title_full_unstemmed | Characterising the Namaqualand Mudbelt: Chronology, Palynology and Palaeoenvironments |
| title_short | Characterising the Namaqualand Mudbelt: Chronology, Palynology and Palaeoenvironments |
| title_sort | characterising the namaqualand mudbelt chronology palynology and palaeoenvironments |
| topic | Environmental and Geographical Science |
| url | http://hdl.handle.net/11427/4856 |
| work_keys_str_mv | AT graycatherineelizabethdarnell characterisingthenamaqualandmudbeltchronologypalynologyandpalaeoenvironments |