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Holocene environmental and hydrologic change in Cambodia : examples from Tonle Sap Lake and AngkorDay, Mary Beth January 2014 (has links)
No description available.
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Application of intertidal salt-marsh foraminifera to reconstruct late Holocene sea-level change at Kariega Estuary, South Africa.Strachan, Kate Leigh. January 2013 (has links)
Unclear predictions surrounding climate change, associated sea-level rise and potential impacts upon coastal
environments have placed an emphasis on the importance of sea-level change. Past sea-level fluctuations
have been measured using biological and geomorphological forms of evidence. One such biological proxy is
salt-marsh foraminifera, which have been used as a high-resolution indicator of past sea-level change, based
on the assumption that surface foraminiferal assemblages are similar in composition to buried fossil
foraminifera. In South Africa, there is ongoing research seeking to produce high-resolution records of sealevel
change, however foraminifera remain an underutilized source of proxy evidence. This research applies
salt-marsh foraminifera as precise indicators of relative sea-level change at Kariega Estuary on the Eastern
Cape coastline of South Africa. Distributions of modern foraminiferal assemblages were investigated,
revealing vertical zonation across the intertidal zone. The foraminiferal and marsh vegetation zones were in
part similar and overlapped to a certain extent, identifying three zones; high, low and tidal flats. This
suggested foraminiferal distribution is a direct function of elevation relative to tidal fluctuation. A 94 cm
core consisting of peat, sand and clay sediments was extracted from the salt marsh. A chronological
framework for the core was based on five AMS radiocarbon age determinations of both bulk sediment and
shell fragment samples placing the record within the last 1500 years Before Present (BP). The basal shell age
was a clear outlier to all bulk sediment ages, possibly as a result of shell recrystallisation. The bulk sediment
age determinations suggested two possible age reversals, potentially linked to sedimentary hiatus or
contamination. These inconsistencies in the chronology were best viewed as separate age models. The core
was analysed at a high resolution, whereby fossil foraminifera were extracted every 2 cm’s down the core. A
transfer function was applied to calculate the former elevation at which each core sample once existed, to
produce a relative sea-level reconstruction. The reconstruction was related to the age models to produce two
possible sea-level curve scenarios. Reconstructed curves from both scenarios depict a 0.5 m (±0.16 m) sealevel
highstand at 1500 cal years BP followed by a lowstand of -0.6 m (±0.03 m). Scenario One reached its
lowest recorded sea-level between 600 cal years BP and 500 cal years BP and then fluctuated below present
day levels. Scenario Two reached its lowest recorded sea-level around 1200 cal years BP, followed by low
amplitude fluctuations and a relatively stable period from 100 cal years BP till the present day. The 1500 cal
years BP highstand recorded for both scenarios correlates well with existing palaeoenvironmental literature
from the southern African coastline. Chronological limitations associated with the remainder of the record
hinder inter-comparison with previous studies. The outcomes of this research suggest that intertidal saltmarsh
foraminifera demonstrate enormous potential for the high-resolution reconstruction of relative sealevel
change in the South African context. / Thesis (M.Sc.)-University of KwaZulu-Natal, Pietermaritzburg, 2013.
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A 40,000-year record of vegetation and fire history from the Tate Vondo region, Northeastern Southpansberg, South Africa.Baboolal, Deeva Lata. 30 June 2014 (has links)
Records from the Quaternary period are used to confirm possible inferred climatic changes,
reveal the responses of species to these changes, and serve as an archive against which
modern environmental dynamics can be assessed. Fueled by a need to understand current
climatic changes, the call for palaeoclimatic research in the southern African subregion has
become more compelling. In southern Africa, such research has been largely restricted to
springs and swamps as the subregion lacks natural lakes, with some exception of a few
coastal lakes such as Lake Sibaya and Lake Eteza. Due to the arid and semi-arid landscapes
which prevail in southern Africa, there is a paucity of suitable sedimentary deposits in the
region. The highly organic peat deposit of Mutale Wetland, situated in the Tate Vondo region
of the northeastern Soutpansberg presents an ideal opportunity for conducting
palaeoenvironmental research. The Mutale Wetland contains relatively old sediments dating
back to >30,000 cal years BP, placing this record within the late Quaternary period.
Palaeoenvironmental techniques including radiocarbon, pollen and charcoal analyses were
applied to produce a palaeoenvironmental reconstruction for Tate Vondo. A 302 cm
sedimentary core was extracted from the Mutale Wetland. Detailed analyses show that prior
to ca. 34,000 cal yr BP, conditions were fairly warm and dry. This is inferred from a
dominance of open grassland vegetation. An expansion of Podocarpus forests together with
an increase in fynbos elements suggest a shift to cool, subhumid conditions during the LGM.
Cooler conditions persisted until ca. 12,000 cal yr BP. Thereafter, a climatic amelioration
was experienced. The appearance of low charcoal concentrations throughout the late
Pleistocene suggests that fire was infrequent. Between ca. 4000 – 1500 cal yr BP, conditions
became warmer and drier, inferred from the development of arid savanna vegetation. The
sharp increase in charcoal after ca. 4000 cal yr BP, broadly coinciding with the arrival of the
first agriculturalists in the area, has implications for the history of human occupation in the
Soutpansberg rather than shifts in climate. The succession from savanna to fynbos vegetation
together with expanded forests implies a return to cool and moist conditions from ca. 1500 –
400 cal yr BP. Arid savanna persists from ca. 400 to the present, implying warmer and drier
conditions towards the present day. Furthermore, from ca. 400 cal yr BP, the pollen and
charcoal record indicate that the majority of recent changes in vegetation have been driven by
anthropogenic activity. This record has contributed to an improved understanding of late
Quaternary changes in climate, vegetation history and human impact in the northeastern
Soutpansberg. / Thesis (M.Sc.)-University of KwaZulu-Natal, Durban, 2014.
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