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This work have quantitatively determine the catchment variables controlling the sinuosity transition of non-valley constrained DFS channels in Alaska, Himalaya and the Andes. Results from the characterisation of channel sinuosity were used through regression analyses to determine the catchment and channel bed parameters controlling reach sinuosity trend and transition of fluvial channel planforms in order to infer a control on the heterogeneity of DFS in the rock record. The catchment approach used was necessary because the studied fluvial systems are associated with DFS (which are regarded as larger forms of alluvial fans) and catchment based approach have been used to investigate controls on alluvial fan morphology. In addition, catchment based investigations are rare in the analyses of the discriminant functions that are considered as controlling factors on channel sinuosity and planform employed previously in the tributary systems. Two distinct channel types were found through the characterisation of 553 reaches of fluvial channels in 3 different modern continental sedimentary basins; channels with no transition in sinuosity/planform (group 1), and channels with transition in sinuosity/planform (group 2) Among the channel bed and catchment quantitative variables investigated in this work, catchment area is the only parameter that shows a general relationship with the channel distance from the apex to the transition point in channel sinuosity through the overall regression results. The result shows that the bigger the catchment area the longer the transition point which is related to a higher water and sediment discharge. Thus, the point at which the channel sinuosity transition will occur can be predicted from the catchment area through the regression equation [y=0.0017x + 28] of the overall linear regression line, where x is the catchment area and y is the channel distance from the apex to the point of transition in channel sinuosity. As the studied channels are associated with DFS, this relation also reflects the prediction of the transition point in the DFS fluvial styles in the rock record. Overall regression analysis results show statistically poor results for the relationship between catchment elevation, catchment slope, channel bed elevation, channel bed slope and either the channel sinuosity or the sinuosity transition. However, in all the three study areas, the majority of the datasets show a trend with the catchment area/sinuosity transition relationship. Additionally, the study area with mainly the biggest catchments (longer channel sinuosity transition) is associated with the highest catchment slope, lowest channel bed elevation and more anabranching channels. Also, the study area with mainly the smallest catchments (shorter channel sinuosity transition) is associated with lower catchment slope, higher channel bed elevation and fewer anabranching channels. This suggests that the higher water and sediment discharge may be related to the steeper slopes and the anabranching channels may reflect the lower channel bed elevation. However, deviations obeserved in the overall regression result in the three study areas are attributed to the differences in the climatic, geologic and tectonic factors in the 3 settings. Although, the differences in these study areas have been shown, nevertheless the interpretations cannot be substantiated in this work with the available data. Thus, there is need for further research to prove any conclusive relationship between these factors and hence remains an issue of debate. In conclusion, this work shows that catchment area is an important controlling parameter on the transition in channel sinuosity of non-valley constrained DFS channels and consequently reflects a a control on the transition in spatial variations of the associated DFS in the rock record.

published_or_final_version / Geography and Geology / Master / Master of Arts

Oblique dunes have orientations that are intermediate between those of transverse and longitudinal dunes. The oblique dunes studied are reversing dunes which undergo no net annual migration when associated with normal meteorological patterns. From April 1980 through September 1980, the dunes migrated up to 65 feet (19.8 m) northwestward under the influence of prevailing onshore winds. High velocity northerly winds (November 1980 through February 1981), associated with the passage of winter frontal systems, caused the dunes to rapidly migrate 65 feet (19.8 m) southward. Volumes of sand transported by these strong winds were commonly reduced by accompanying rainfall. In October 1980 and March 1981 neither wind direction was dominant, and frequent changes in wind direction caused many of the dunes to become flattened. Hurricanes, which strike the area in late summer, have had no lasting effects on the dunes. Three major stratification types were observed in trenches and on etched surfaces. Translatent strata were deposited by wind ripples; grainfall deposits accumulated when saltating grains settled on leeward slopes of the dunes, and grainflow cross-strata were developed by avalanching on leeward slopes. Preservation of these stratification types occurred in zones of net deposition, predominantly leeward of the dune crests. Strata deposited during the summer wind regime dip northeast, whereas the winter strata dip in a southerly direction. The winter deposits are best preserved in the central cores of the dunes. This suggests that either the high velocity winds of the initial winter frontal systems destroy large volumes of the summer deposits, or that the dunes migrate southward, under the influence of dry northerly winds, during droughts. Oblique dune deposits should be difficult to discern in the rock record, because they may contain aspects of either transverse or longitudinal dunes. It is likely that some ancient oblique dunes have been mistakenly described as other dune types in the literature. / text

The Lake Heron basin is an intermontane basin located approximately 30 kms west of Mount Hutt. Sediments within the basin are derived from a glacier that passed through the Lake Stream Valley from the upper Rakaia Valley. The lack of major drainage in the south part of the basin has increased the preservation potential of glacial phenomena. The area provides opportunities for detailed glacial geomorphology, sedimentology and micropaleontogical work, from which a very high-resolution study on climate change spanning the Last Glacial Maximum (LGM) through to the present was able to be reconstructed. The geomorphology reveals a complex glacial history spanning multiple glaciations. The Pyramid and Dogs Hill Advance are undated but possibly relate to the Waimaungan and Waimean glaciations. The Emily Formation (EM), previously thought to be MIS 4 (Mabin, 1984), was dated using Be10 to c. 25 ka B.P. The EM was largest advance of the Last Glacial Maximum (LGM). Ice during the LGM was at least 150m thicker than previously thought, as indicated by relatively young ages of high elevation moraines. Numerous moraine ridges and kame terraces show a continuous recession from LGM limits, and, supported by decreasing Be10 ages for other LGM moraines, it seems ice retreat was punctuated by minor glacial readvances and still-stands. These may be associated with decadal-scale climate variations, such as the PDO or early ENSO-like systems. There are relatively little sedimentological exposures in the area other than those on the shores of Lake Heron. The sediment at this location demonstrates the nature of glacial and paraglacial sedimentation during the later stages of ice retreat. They show that ice fronts oscillated across several hundred metres before retreating into Lake Heron proper. Vegetation change at Staces Tarn (1200m asl) indicates climate amelioration in the early Holocene. The late glacial vegetation cover of herb and small shrubs was replaced by a low, montane forest about 7,000 yrs B.P, approximately at the time of the regional thermal maxima. From 7,000 and 1,400 yrs B.P, temperatures slowly declined, and grasses slowly moved back onto the site, although the montane forest was still the dominant vegetation. Fires were frequent in the area extending back at least 6,000 years B.P. The largest fire, about 5,300 yrs B.P, caused major forest disruption. But full recovered occurred within about 500 years. Beech forest appears at the site about 3,300 yrs B.P and becomes the dominant forest cover about 1,400 yrs B.P. Cooler, cloudier winters and disturbance by fire promoted the expansion of beech forest at the expense of the previous low, montane forest. Both the increased frequency of fire events and late Holocene beech spread may be linked to ENSO-related variations in rainfall. The youngest zone is characterised by both a dramatic decline in beech forest and an increase in grasses, possibly representing human activity in the area.

28 pp. / Arizona Watershed Stewardship Guide / Stream Processes for Watershed Stewards describes the basic concepts, processes and features of streams in Arizona and in general. The is designed as a tool for land owners, managers, and others to learn about the physical, chemical and biological attributes of streams as they evolve. These concepts can then be applied to better stream management.

Rates of latest Quaternary slip obtained from stream terraces and glacial moraines displaced by faults of the Alpine shear system vary with space and time. Field measurements yield displacement values for faulted geomorphic surfaces, while the rate of thickening of weathering rinds and changes in soil properties, calibrated at sites of known age, yield age estimates. Precisions are 5-20% from weathering rinds and 15-50% from soil data. The oldest surfaces examined have ages of 15-20 ka and right-lateral fault displacements up to 400-600 m. Latest Quaternary lateral-slip rates are 20-45 mm/yr across the Alpine fault in the Southern Alps. To the northeast slip is distributed across a system of faults in Marlborough. The main faults of this shear system--the Wairau, Awatere, Clarence, Hope, and Porters Pass--have latest Quaternary rates of 5-10, 7-10, 7-9, 20-40, and 4-5 mm/yr respectively. Each fault has undergone a substantial decrease in lateral slip in the last 3-5 ka. Long-term rates of horizontal slip across the Australian-Pacific plate boundary--the Alpine shear system in most of the South Island--are 35-50 mm/yr parallel and 8-25 mm/yr normal. Sums of fault-slip rates exceed these plate motions for the early-middle Holocene, but late Holocene fault-slip rates are less than half the long-term average. Rates of geodetic strain and seismic moment release over the last 50-100 yr approximate the long-period rates in Marlborough but are only half in the Southern Alps. The best explanations of these variabilities are that the proportion of plate-boundary motion accommodated by fault slip changes, or that the rate of motion across the plate boundary varies, perhaps over 5 ka intervals. The first hypothesis is not consistent with the early Holocene rates exceeding the long-term average, but the second hypothesis implies that the last 50-100 yr is a period of renewed high tectonic activity. The second hypothesis is more consistent with the data, and the last 15-20 ka may be the time interval necessary to average out shorter, 5 ka episodic variations in plate-boundary motions.

The application of geological and geophysical methods on the Ionian Island of Kefalonia has provided a new-found basis by which to test the hypothesis that Ancient Ithaca, the home of Odysseus as described in Homer’s epic the Odyssey, a subject which has perplexed academics for centuries. Although popular belief places Odysseus’ homeland on Ithaki, a small mountainous island lying to the east of Kefalonia, its location does not fit Homer’s descriptions of Ancient Ithaca since it is described as a “low-lying” island lying “furthest to the west” (facing dusk not dawn). Being land-locked and connected to the rest of Kefalonia by a narrow (6 km x 2 km) isthmus called the Thinia valley, the Paliki Peninsula of Western Kefalonia provides a better geographical fit. However, it has generally been dismissed as a candidate for Ancient Ithaca since it is not an island today and the topography of the connecting isthmus rises to a height of c. 200 m along the centre of the Thinia valley. Despite these obstacles and based on a quote by the ancient geographer Strabo made around 1 BC, Bittlestone et al. (2005) proposed that during the Mycenaean Era an ancient seaway (“Strabo’s Channel”) could have existed where Thinia stands today and the valley’s present topography is due to landslide deposition which eventually closed the seaway. This thesis presents the results of a 3-year geological, geomorphological and geophysical investigation of “Strabo’s Channel”. The investigation was carried out using a survey programme of complimentary non-invasive geophysical techniques calibrated by 17 shallow sedimentary cores and combined with surface geological mapping and geomorphological observations. In addition to a helicopter-mounted electromagnetic (HEM) survey acquired for Northern Paliki, gravity measurements were taken across the Thinia isthmus, and resistivity and seismic refraction surveys were carried out at strategic sites. Marine shallow seismic reflection surveys were also undertaken in the coastal areas adjacent to the isthmus to chart postglacial transgression into these shallow coastal areas and to reconstruct the paleo-geography of Northern Paliki since the Last Glacial Maximum (LGM) (c. 21 500 BP). The survey area is sited in the Pre-Apulian isopic zone of the Hellenide thrust belt which represents a structurally-inverted passive continental margin subsequently affected by foreland contraction and overprinted by neotectonic (outer-arc) deformation resulting from African-Eurasian plate collision. The results showed that the geology and geomorphology of Thinia was far more complicated than originally believed. The bedrock geology records the Cretaceous-Quaternary evolution of an extensional-compressional regime brought about through the foreland-migration of the Hellenide fold-and-thrust deformation in the Early Miocene which reactivated earlier south-easterly-dipping extensional faults. The peninsula was affected by further Late Quaternary, Holocene and recent neotectonic deformation caused by the formation of the dextral Kefalonia Transform Fault (KTF) and slope failure resulting from the generation of steep slopes. The shallow marine seismic reflection survey showed clear differentiation between the tectonised “pre-Holocene” and onlapping postglacial sediments separated by a prominent erosional surface associated with the LGM sea level lowstand of -120 m. The survey detected a buried drainage valley deeply-incised into the pre-Holocene of the Gulf of Argostoli indicating that a major glacial river drained from Thinia during this lowstand. During postglacial sea level rise this valley was infiltrated by marine waters to form a ria, flooding two large glacial lakes which acted as depocentres for postglacial sediments. While the prevalence of slope collapse of the steep valley sides in Thinia favoured the idea that “Strabo’s Channel” was infilled through repeated deposition of landslide debris, the presence of bedrock at the surface of Thinia ruled out the possibility that the present valley topography was built-up through Late Holocene deposition of landslide material between Kefalonia and Paliki. The onshore tests confirmed the presence of a thick deposit of steeply-dipping and tectonised marine sediments within the valley. Biostratigraphic analysis of core samples dated these as Early Miocene to Early Pleistocene (Gelasian) indicating marine waters existed along the valley until at least 1.80 million years ago, an order of magnitude younger than previously reported in the area. However, no new independent sediment younger than Early Pleistocene was retrieved in the cores obtained for this study despite the findings of an earlier borehole which appeared to contain Late Quaternary and Holocene marine fauna (Ehux). The geophysical surveys and cores failed to detect the sides or bottom of a channel or evidence of substantial clastic debris within the proposed channel route thus ruling out the possibility that a buried marine-level channel which extended from “sea-to-sea” had existed during the Late Bronze Age. One strategic area of investigation was the upland site of a suspected paleo-lake (Lake Katachori) which overlapped the proposed route of Strabo’s Channel at ~170 m elevation. Although the presence of freshwater algae within the upper few metres confirmed a lacustrine environment, the geophysical and core evidence showed it was shallow (6 m thick) and was sited on steeply easterly-dipping Plio-Pleistocene sediments uplifted to ~170 m above sea level. The occurrence of freshwater algae admixed with uppermost Plio-Pleistocene sediments probably represents a basal reworked basal lag deposit thus, implying departure from marine depositional setting occurred in Thinia sometime after the Gelasian (1.80 Ma). Coring at Livadi Marsh suggested that while the marsh was flooded during the Bronze Age to a depth of c. 1.2 m, making it a candidate for Ancient Ithaca’s harbour, no significant coseismic uplift appears to have occurred since the Late Bronze Age. Current coastal position was due to progradation and aggradation of marsh sediments with no more than 1.2m of coseismic uplift. The lack of Holocene-Late Quaternary sediment relating to an uplifted marine channel and the presence of Lake Katachori may tentatively be explained through the uplift and westwards translation of the sediments of central Thinia through establishment of a contractional-extensional linked gravity driven rotational slip linking the listric “Agia Ioanni Fault” with the Atheras Thrust. The boreholes detected shear-thrusting and steep dips within the Miocene and Plio-Pleistocene marl sediments demonstrating that the area experienced strong tectonic dislocation which is in favour of this model however further tests are required to investigate this and whether it could feasibly have occured in the required timescale.

Palaeoglacier margins from the Zanskar Range of the north-western Indian Himalaya are reconstructed through geomorphological mapping and sedimentology. These are dated ilsing Optically Stimulated Luminescence (OSL) techniques on quartz extracted from related fluvioglacial and lacustrine deposits. A glaciated palaeosurface with broad, gentle slopes >280m above river level and high grade metamorphic erratics represents the oldest and most extensive glaciation, the Chandra Stage. This formed an ice-cap with its ice-shed to the south over the High Himalaya. A change from broad glacial troughs to narrow V -shaped gorges along with large subdued moraine ridges and drift/erratic limits defines an extensive valley glaciation, the Batal Stage, with its maximum close to -78.0±12.3ka BP (Oxygen Isotope Stage (OIS) 4). Distinct sets of moraine ridges represent a less extensive glaciation, the Kulti Stage, which is dated to shortly after the global Last Glacial Maximum (OIS 2) and a minor advance, the Sonapani, is represented by sharp crested moraine ridges < 2km from current ice bodies. The change in glacier extent and style from the Chandra Stage to the later glaciations may be related to uplift of more southerly ranges blocking monsoon precipitation and incision of the landscape such that ice reached lower altitudes over shorter horizontal distances. Batal and Kulti Stage Glacier Elevation Indexes (GEls) calculated for this and adjacent areas increase from south-west to the north-east, but decrease again towards the Indus valley, reflecting attenuation of the south-westerly monsoon and possible channelling of westerly depressions along the broad upper Indus valley. GEl values were depressed by ~500m during the Batal Stage and -300m during the Kulti Stage. Six new OSL age estimates from the Zanskar Range greatly improve the glacial chronology of the north-west Himalaya and reinforce the emerging asynchrony between this region and the Central and Eastern Himalaya, which experienced its maximum glaciation during OIS 2 rather than OIS 4. Improved glacier mass balance data, palaeoclimatic proxy data for the summer monsoon and particularly the winter westerlies, and numerical age estimates from Himalayan glaciers are required to explain this asynchronous maximum.

A thesis submitted to the Faculty of Science, University of the Witwatersrand, in fulfillment of the requirements for the degree of Doctor of Philosophy. Johannesburg, 1998 / The appearance of the dry Molopo River with its generally wide and shallow valley cut into the Kalahari Group sediments, but more especially its few impressive rock-cut gorges, has intrigued many people over the ages, and led to many theories concerning its history. The rock-cut gorges, in particular, have traditionally been attributed to ancient, previously much more extended drainage lines, more or less in the same geographical position as the present Molopo Valley. An analysis of the sediment body of the Kalahari Group, and both, alluvial gravels and geomorphic features on the rim of the Cainozoic Kalahari Basin, have indicated that the Molopo drainage has gradually shifted westward over time, in response to a tilting of the drainage area, which lies across the south-eastern rim of the Kalahari Basin, The present geographical position of the Molopo River is thus a relatively recent one in its evolution. The earliest traces of drainage lines in the area predate the Permo-Carboniferous glaciation of Gondwana. A preglaciation valley system with only some similarities to the present-one flowed in a northwesterly direction. There is a long hiatus in the evidence from the end of the glaciation to the beginning of the formation of the Calnozoic Kalahari Basin. The most significant feature of that intermediate period, is a large meteorite impact which occurred near Morokweng at the J-K boundary. The Cainozoic evolution of the Molopo drainage has been strongly influenced by both tectonics and climatic change. Tectonics, which include both the initial formation of the Kalahari Basin and Neogene warpings of the intra-continental axes of uplift, caused the interruption of a pre- Kalahari southward flowing drainage system, an extended upper Molopo, the existence of the Molopo as an endoreic system for an extended period of time, and a westward shift of the entire Molopo drainage system. Progressively more arid conditions interrupted by humid climatic pulses of decreasing intensity have occurred since the Cretaceous. The aridifying conditions caused the existence of playa-like conditions over long periods oftime in the back-tilted section of the proto-Molopo. This was followed by a rapid sediment infilling of the sub-basin and a major rejuvenation phase, which caused the incision of the Molopo River into the duricrusted sediments of the Kalahari Group, and the re-establishment of the Molopo River as an exoreic drainage system in its present position. Rock-cut terrace remnants in the upper Molopo give evidence of much smaller climatic changes during the Quaternary. There has been no integrated flow in living memory.