Feeding ecology of the cichlid fish Sarotherodon Mossambicus in Lake Sibaya, KwaZulu
- Authors: Bowen, Stephen H
- Date: 1977
- Subjects: Cichlids -- Ecology , Fishes -- Ecology -- South Africa -- KwaZulu-Natal -- Sibaya, Lake
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5837 , http://hdl.handle.net/10962/d1009688 , Cichlids -- Ecology , Fishes -- Ecology -- South Africa -- KwaZulu-Natal -- Sibaya, Lake
- Description: The feeding of the cichlid fish Sarotherodon mossambicus in Lake Sibaya, KwaZulu, was studied in relation to various biotic and abiotic features of the l ake environment from January, 1973 to July, 1975. The primary goal of the study was to determine the cause of stunting and poor condition of adults in this population. Juvenile and adult S. mossambicus feed on a mixture of detritus, bacteria and diatoms that occurs as a flocculent layer on sand substrates throughout the lake. Concentrated gastric acid, commonly at pH values of 1.5 and lower, lyses diatoms and bacteria which are subsequently digested in the intestine. This is the first report of digestion of bacteria by a fish, and the nutritional significance of the finding is discussed. Juveniles feed predominantly on shallow sand terraces found along the margin of much of the lake, while adults usually feed in offshore waters at depths of 3 m and greater. Benthic floc from feeding areas of juveniles and adults have similar concentrations of organic matter, total carbohydrate, soluble carbohydrate and calories, but differ markedly in respect to diatom and protein concentration. Diatom concentrations are generally high in terrace floc but are consistently low in floc from deep water. Protein concentration of benthic floc decreases with increasing depth from 0 - 5 m. Partial correlation analysis shows that protein and diatom concentrations have no correlation independent. of their common relationship to depth, and the evidence implicates detrital bacteria as the primary source of protein in benthic floc. Probable causes of the observed distributions of diatoms and protein are discussed. The protein content of benthic floc profoundly influences its nutritional value. A comparison with available data on animal nutrition shows that the ratio of digestible protein to digestible energy in floc in the shallows is high enough that this food resource would be expected to support good growth, but the ratio for deep water floc is so low that it would be expected to result in conspicuous malnutrition. Thus, inadequate dietary protein is identified as the principal cause of stunting and poor condition of adult S· mossambicus in Lake Sibaya; It is argued that the ratio of digestible protein to digestible calories can be expected to determine the food value of particulate organic matter that includes amorphous detritus in other ecosystems. Despite stunting and poor condition of adults, S. mossambicus are abundant in Lake Sibaya. The precocious breeding of this population is discussed as an adaptation that allows it to maximize reproductive output given the limited resources available to adults. Juvenile S. mossambicus perform daily movements from deep water onto the terraces where they feed and then back into deep water. During periods of relatively low lake level when terrace waters were usually less than 1.5 m deep (1-73 to 1-74), juveniles were present on the terrace throughout daylight hours. At relatively high lake levels (7-74 to 8-75), juveniles were present on the terraces for only about five hours following sunset. Periods of heavy wave action interrupt feeding activity and result in reduced numbers of fish in terrace waters. The possible roles of predator avoidance and temperature in determination of daily feeding behavior are discussed. Daily energy assimilation by juveniles, estimated by a field technique, is approximately 115 cal per g fish dry weight.
- Full Text:
- Date Issued: 1977
- Authors: Bowen, Stephen H
- Date: 1977
- Subjects: Cichlids -- Ecology , Fishes -- Ecology -- South Africa -- KwaZulu-Natal -- Sibaya, Lake
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5837 , http://hdl.handle.net/10962/d1009688 , Cichlids -- Ecology , Fishes -- Ecology -- South Africa -- KwaZulu-Natal -- Sibaya, Lake
- Description: The feeding of the cichlid fish Sarotherodon mossambicus in Lake Sibaya, KwaZulu, was studied in relation to various biotic and abiotic features of the l ake environment from January, 1973 to July, 1975. The primary goal of the study was to determine the cause of stunting and poor condition of adults in this population. Juvenile and adult S. mossambicus feed on a mixture of detritus, bacteria and diatoms that occurs as a flocculent layer on sand substrates throughout the lake. Concentrated gastric acid, commonly at pH values of 1.5 and lower, lyses diatoms and bacteria which are subsequently digested in the intestine. This is the first report of digestion of bacteria by a fish, and the nutritional significance of the finding is discussed. Juveniles feed predominantly on shallow sand terraces found along the margin of much of the lake, while adults usually feed in offshore waters at depths of 3 m and greater. Benthic floc from feeding areas of juveniles and adults have similar concentrations of organic matter, total carbohydrate, soluble carbohydrate and calories, but differ markedly in respect to diatom and protein concentration. Diatom concentrations are generally high in terrace floc but are consistently low in floc from deep water. Protein concentration of benthic floc decreases with increasing depth from 0 - 5 m. Partial correlation analysis shows that protein and diatom concentrations have no correlation independent. of their common relationship to depth, and the evidence implicates detrital bacteria as the primary source of protein in benthic floc. Probable causes of the observed distributions of diatoms and protein are discussed. The protein content of benthic floc profoundly influences its nutritional value. A comparison with available data on animal nutrition shows that the ratio of digestible protein to digestible energy in floc in the shallows is high enough that this food resource would be expected to support good growth, but the ratio for deep water floc is so low that it would be expected to result in conspicuous malnutrition. Thus, inadequate dietary protein is identified as the principal cause of stunting and poor condition of adult S· mossambicus in Lake Sibaya; It is argued that the ratio of digestible protein to digestible calories can be expected to determine the food value of particulate organic matter that includes amorphous detritus in other ecosystems. Despite stunting and poor condition of adults, S. mossambicus are abundant in Lake Sibaya. The precocious breeding of this population is discussed as an adaptation that allows it to maximize reproductive output given the limited resources available to adults. Juvenile S. mossambicus perform daily movements from deep water onto the terraces where they feed and then back into deep water. During periods of relatively low lake level when terrace waters were usually less than 1.5 m deep (1-73 to 1-74), juveniles were present on the terrace throughout daylight hours. At relatively high lake levels (7-74 to 8-75), juveniles were present on the terraces for only about five hours following sunset. Periods of heavy wave action interrupt feeding activity and result in reduced numbers of fish in terrace waters. The possible roles of predator avoidance and temperature in determination of daily feeding behavior are discussed. Daily energy assimilation by juveniles, estimated by a field technique, is approximately 115 cal per g fish dry weight.
- Full Text:
- Date Issued: 1977
5-hydroxytryptamine and sexual behaviour in rhesus monkeys
- Authors: Gradwell, Peter Bertram
- Date: 1976
- Subjects: Rhesus monkey -- Behavior Sexual behavior in animals
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3210 , http://hdl.handle.net/10962/d1012086
- Description: Selective inhibition of 5-hydroxytryptamine by parachlorophenylalanine (PCPA) is able to restore sexual receptivity in female rhesus monkeys made unreceptive by bilateral adrenalectomy. PCPA in the doses used reduces the levels of 5-hydroxyindoleacetic acid (5HIAA) in the cerebrospinal fluid to 40 per cent of the normal oestradioltreated condition. Both the increased sexual receptivity and the lowered 5HIAA levels "in the CSF are in turn reversed by 5-hydroxytryptophal (5HTP), the irrmediate precursor of 5HT and the substance whose synthesis is inhibited by PCPA. 5HTP on its own reduces sexual receptivity and increases 5HIAA levels in the CSF of ovariectomised, oestradiol-treated (but otherwise intact) female rhesus monkeys. A substance other than an adrenal androgen has therefore been shown to restore sexual receptivity in adrenalectomised female monkeys . Testosterone propionate and oestradiol benzoate both lower the turnover rates of 5HT in the brains of ovariectomised female monkeys, as measured by the 2 hour probenecid test. Taken together, these findings suggest that adrenal androgens could act on specific sites in the female monkey brain via 5HT-containing neural systems, to control (or at least influence) sexual receptivity. All the results of administering oestradiol to ovariectomised monkeys in these experiments are consistent with the established roles of this hormone in female sexual attractiveness and in the gonadotrophin- controlling systems of the hypothalamo-hypophyseal axis. In contrast to these findings on 5HT and sexual receptivity in female monkeys, no clear role for 5HT- containing neural systems could be demonstrated in the grooming, aggressive or social behaviours of female monkeys. No clear role for 5HT could be demonstrated in the refractory period following ejaculation in male monkeys , or when testosterone replacement is given to castrated male monkeys.
- Full Text:
- Date Issued: 1976
- Authors: Gradwell, Peter Bertram
- Date: 1976
- Subjects: Rhesus monkey -- Behavior Sexual behavior in animals
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3210 , http://hdl.handle.net/10962/d1012086
- Description: Selective inhibition of 5-hydroxytryptamine by parachlorophenylalanine (PCPA) is able to restore sexual receptivity in female rhesus monkeys made unreceptive by bilateral adrenalectomy. PCPA in the doses used reduces the levels of 5-hydroxyindoleacetic acid (5HIAA) in the cerebrospinal fluid to 40 per cent of the normal oestradioltreated condition. Both the increased sexual receptivity and the lowered 5HIAA levels "in the CSF are in turn reversed by 5-hydroxytryptophal (5HTP), the irrmediate precursor of 5HT and the substance whose synthesis is inhibited by PCPA. 5HTP on its own reduces sexual receptivity and increases 5HIAA levels in the CSF of ovariectomised, oestradiol-treated (but otherwise intact) female rhesus monkeys. A substance other than an adrenal androgen has therefore been shown to restore sexual receptivity in adrenalectomised female monkeys . Testosterone propionate and oestradiol benzoate both lower the turnover rates of 5HT in the brains of ovariectomised female monkeys, as measured by the 2 hour probenecid test. Taken together, these findings suggest that adrenal androgens could act on specific sites in the female monkey brain via 5HT-containing neural systems, to control (or at least influence) sexual receptivity. All the results of administering oestradiol to ovariectomised monkeys in these experiments are consistent with the established roles of this hormone in female sexual attractiveness and in the gonadotrophin- controlling systems of the hypothalamo-hypophyseal axis. In contrast to these findings on 5HT and sexual receptivity in female monkeys, no clear role for 5HT- containing neural systems could be demonstrated in the grooming, aggressive or social behaviours of female monkeys. No clear role for 5HT could be demonstrated in the refractory period following ejaculation in male monkeys , or when testosterone replacement is given to castrated male monkeys.
- Full Text:
- Date Issued: 1976
A study of factors affecting precision in atomic absorption spectrometry
- Roos, Johannes Tielman Hofmeyr
- Authors: Roos, Johannes Tielman Hofmeyr
- Date: 1976
- Subjects: Atomic absorption spectroscopy
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4490 , http://hdl.handle.net/10962/d1013080
- Description: 1. The effect of deviations from Beer's law on the precision of atomic absorption analysis has been examined from a theoretical point of view, and a function has been derived which makes it possible to evaluate quantitatively the effect of calibration curvature on the precision of analysis. The influence of incomplete sample volatilization on calibration curvature has been briefly investigated. 2. Possible error sources in atomic absorption spectrometry have been classified according to the "error function" (i.e., the dependence, upon transmittance T, of the uncertainty dT in a given transmittance measurement) with which they are associated. The magnitude of the contribution from each component function to the overall error function has been evaluated quantitatively, and it has been shown that the major component in nearly every case examined is that associated with the dynamic nature of the flame. Concentration ranges for optimum precision are suggested. 3. The effect of varying instrumental parameters on precision has been investigated, and generalized conditions for best precision have been ascertained. 4. The effect of an initial solvent extraction step on the precision of atomic absorption has been investigated for the elements copper and lead. It is shown that solvent extraction may be used to improve both the analytical sensitivity and the precision of analysis when very low concentrations of metal are determined. 5. The precision of analytical methods involving atomic absorption spectrometry has been studied, and the standard deviations compared with those obtained for the analysis of similar samples by means of a variety of other methods of analysis, both instrumental and classical.
- Full Text:
- Date Issued: 1976
- Authors: Roos, Johannes Tielman Hofmeyr
- Date: 1976
- Subjects: Atomic absorption spectroscopy
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4490 , http://hdl.handle.net/10962/d1013080
- Description: 1. The effect of deviations from Beer's law on the precision of atomic absorption analysis has been examined from a theoretical point of view, and a function has been derived which makes it possible to evaluate quantitatively the effect of calibration curvature on the precision of analysis. The influence of incomplete sample volatilization on calibration curvature has been briefly investigated. 2. Possible error sources in atomic absorption spectrometry have been classified according to the "error function" (i.e., the dependence, upon transmittance T, of the uncertainty dT in a given transmittance measurement) with which they are associated. The magnitude of the contribution from each component function to the overall error function has been evaluated quantitatively, and it has been shown that the major component in nearly every case examined is that associated with the dynamic nature of the flame. Concentration ranges for optimum precision are suggested. 3. The effect of varying instrumental parameters on precision has been investigated, and generalized conditions for best precision have been ascertained. 4. The effect of an initial solvent extraction step on the precision of atomic absorption has been investigated for the elements copper and lead. It is shown that solvent extraction may be used to improve both the analytical sensitivity and the precision of analysis when very low concentrations of metal are determined. 5. The precision of analytical methods involving atomic absorption spectrometry has been studied, and the standard deviations compared with those obtained for the analysis of similar samples by means of a variety of other methods of analysis, both instrumental and classical.
- Full Text:
- Date Issued: 1976
Agnation, alternative structures, and the individual in Chopi society
- Authors: Webster, D J
- Date: 1976
- Subjects: Chopi (African people) , Ethnology -- Mozambique
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:2122 , http://hdl.handle.net/10962/d1013288
- Full Text:
- Date Issued: 1976
- Authors: Webster, D J
- Date: 1976
- Subjects: Chopi (African people) , Ethnology -- Mozambique
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:2122 , http://hdl.handle.net/10962/d1013288
- Full Text:
- Date Issued: 1976
Drummer Hodge : the poetry of the Anglo-Boer War (1899-1902)
- Authors: Van Wyk Smith, Malvern
- Date: 1976
- Subjects: War poetry -- History and criticism South African War, 1899-1902 -- Literature and the war South African War, 1899-1902 -- Art and the war
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:2252 , http://hdl.handle.net/10962/d1003919
- Description: From Preface: This is not a history of the Boer War; nor is it an exclusively literary study of the poetry of that war. If the work that follows has to be defined generically at all, it may be called an exercise in cultural history. It attempts to assess the impact of a particular war on the literary culture, especially the poetry, of both the participants and the observers, whether in South Africa, in Britain and the rest of the English-speaking world, or in Europe. An assumption made throughout this study is that war poetry is not only verse written by men who are or have been under fire. Just as 'War poetry is not to be confused with political, polemical, or patriotic verse, although it can contain elements of all of these, so it is also the work of observers at home as much as that of soldiers at the front. It follows that I have not allowed myself the academic luxury of selecting, on the basis of literary merit only, a handful of outstanding war poems for rigorous analysis and discussion. "Doggerel can express the heart" wrote one of these late-Victorian soldierly versifiers, and I have roamed widely in the attempt to assemble the material which, I believe, records the full range of the impact that the Boer War made not only on Briton and Boer, but on the worId at large. A major thesis of this study is that the Boer War marked the clear emergence of the kind of war poetry which we have come to associate almost exclusively with the First World War. Poems in the style and spirit of "The Charge of the Light Brigade" were written in profusion, but the work which serves as this study's masthead, Hardy's "Drummer Hodge," clearly has --like many of its contemporaries-- more in common with Owen's verse than with Tennyson's. The reasons for the appearance of such poetry are discussed in Chapter 1; the rest of the book provides the evidence of it.
- Full Text:
- Date Issued: 1976
- Authors: Van Wyk Smith, Malvern
- Date: 1976
- Subjects: War poetry -- History and criticism South African War, 1899-1902 -- Literature and the war South African War, 1899-1902 -- Art and the war
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:2252 , http://hdl.handle.net/10962/d1003919
- Description: From Preface: This is not a history of the Boer War; nor is it an exclusively literary study of the poetry of that war. If the work that follows has to be defined generically at all, it may be called an exercise in cultural history. It attempts to assess the impact of a particular war on the literary culture, especially the poetry, of both the participants and the observers, whether in South Africa, in Britain and the rest of the English-speaking world, or in Europe. An assumption made throughout this study is that war poetry is not only verse written by men who are or have been under fire. Just as 'War poetry is not to be confused with political, polemical, or patriotic verse, although it can contain elements of all of these, so it is also the work of observers at home as much as that of soldiers at the front. It follows that I have not allowed myself the academic luxury of selecting, on the basis of literary merit only, a handful of outstanding war poems for rigorous analysis and discussion. "Doggerel can express the heart" wrote one of these late-Victorian soldierly versifiers, and I have roamed widely in the attempt to assemble the material which, I believe, records the full range of the impact that the Boer War made not only on Briton and Boer, but on the worId at large. A major thesis of this study is that the Boer War marked the clear emergence of the kind of war poetry which we have come to associate almost exclusively with the First World War. Poems in the style and spirit of "The Charge of the Light Brigade" were written in profusion, but the work which serves as this study's masthead, Hardy's "Drummer Hodge," clearly has --like many of its contemporaries-- more in common with Owen's verse than with Tennyson's. The reasons for the appearance of such poetry are discussed in Chapter 1; the rest of the book provides the evidence of it.
- Full Text:
- Date Issued: 1976
Some problems of dialect lexicography with particular reference to the preparation of a draft of an illustrative, experientially categorised Dictionary of South African English
- Authors: Branford, Jean
- Date: 1976
- Subjects: English language -- Provincialisms -- South Africa -- Dictionaries English language -- South Africa English language -- Lexicography -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3626 , http://hdl.handle.net/10962/d1009689
- Description: This dissertation consists in essence of an experiment and a commentary upon it. The text which constitutes Part II is a lexicographical experiment incorporating some features and treatments not usual in lexicography, and Part I consists of a discussion of the problems encountered, principles applied and procedures followed. Neither the matter nor the manner of the experiment, however, lends itself in the present state of our knowledge to the fully impersonal objectivity that is often claimed for the experiments in the physical sciences. At the same time every effort has been made to establish an unbiased record of the data and to maintain a certain methodological consistency. The main experimental feature of Part II is that it is an attempt to combine an orthodox, alphabetical dictionary with an experiential categorisation of the vocabulary, without repeating the entire data for each type of treatment. This has been done by means of a series of numbered, classified word-lists with a limited subject index as a guide to their use. The entries themselves, instead of being repeated in the order of their classification, are numbered according to the category or categories to which the word defined belongs. It can then, by means of its number(s), be found in its own lexical or experiential set (or sets) in the categorised section. This part of the work might be better described as lexicology rather than lexicography but does, I think, prove itself to be a useful adjunct to the A - Z lexicon proper. Apart from the detailed categorisation system the text contains three features not normally included in dictionaries of small compass: illustrative quotations, etymologies and a number of tentative parallels between South African and other varieties of English by means of cross-references to items of similar or related meaning or form in the English of Australia, Canada, the U.S.A., Hong Kong, Anglo-India and other 'overseas' English speech communities. Introduction, p. 1.
- Full Text:
- Date Issued: 1976
- Authors: Branford, Jean
- Date: 1976
- Subjects: English language -- Provincialisms -- South Africa -- Dictionaries English language -- South Africa English language -- Lexicography -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3626 , http://hdl.handle.net/10962/d1009689
- Description: This dissertation consists in essence of an experiment and a commentary upon it. The text which constitutes Part II is a lexicographical experiment incorporating some features and treatments not usual in lexicography, and Part I consists of a discussion of the problems encountered, principles applied and procedures followed. Neither the matter nor the manner of the experiment, however, lends itself in the present state of our knowledge to the fully impersonal objectivity that is often claimed for the experiments in the physical sciences. At the same time every effort has been made to establish an unbiased record of the data and to maintain a certain methodological consistency. The main experimental feature of Part II is that it is an attempt to combine an orthodox, alphabetical dictionary with an experiential categorisation of the vocabulary, without repeating the entire data for each type of treatment. This has been done by means of a series of numbered, classified word-lists with a limited subject index as a guide to their use. The entries themselves, instead of being repeated in the order of their classification, are numbered according to the category or categories to which the word defined belongs. It can then, by means of its number(s), be found in its own lexical or experiential set (or sets) in the categorised section. This part of the work might be better described as lexicology rather than lexicography but does, I think, prove itself to be a useful adjunct to the A - Z lexicon proper. Apart from the detailed categorisation system the text contains three features not normally included in dictionaries of small compass: illustrative quotations, etymologies and a number of tentative parallels between South African and other varieties of English by means of cross-references to items of similar or related meaning or form in the English of Australia, Canada, the U.S.A., Hong Kong, Anglo-India and other 'overseas' English speech communities. Introduction, p. 1.
- Full Text:
- Date Issued: 1976
Stratigraphy and sedimentology of the Cape and Karoo Sequences in the Eastern Cape Province
- Authors: Johnson, M R
- Date: 1976
- Subjects: Sediments (Geology) -- South Africa -- Eastern Cape Geology, Stratigraphic Sedimentology
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5004 , http://hdl.handle.net/10962/d1005617
- Description: The Cape Supergroup (Sequence) comprises three groups, embracing a total of twenty-three formations, with a maximum combined thickness of approximately 8 km. The Table Mountain Group consists of medium-grained (occasionally fine- or coarse-grained), "clean", ultra-quartzose sandstone plus subordinate fine-grained, "dirty", subfeldspathic to feldspathic sandstone, mudrock, and rhythmitite. Average total thickness is about 3000 m. The Bokkeveld Group is composed of mudrock, rhythmitite and subordinate subfeldspathic to feldspathic sandstone (generally fine-grained and "dirty"), with a maximum total thickness of over 3000 m. The Witteberg Group comprises fine- to medium-grained ultra-quartzose sandstone, icaceous streaky rhythmitite, mudrock, and one thin diamictite unit; total thickness is about 1700 m. The strata belonging to the Cape Supergroup appear to have been largely deposited under marine conditions in environments ranging from outer shelf to beach. Deltaic deposits are,however, common in the upper part of the Bokkeveld Group and the Witteberg Group, while the main sandstone units in the upper third of the Table Mountain Group may have accumulated on a coastal alluvial plain. Deposition took place in a basin elongated in an east-west direction, with the palaeoslope inclined towards the south. Palaeocurrents were generally directed down the palaeoslope, but westerly 1 transport directions parallel to the palaeostrike and presumed shoreline are present in both the Table Mountain and Witteberg Groups. I The sedimentary rocks o~ the Karoo Sequence are subdivided into two groups (containing a total of eleven formations) and four ungrouped formations. Using the maximum thicknesses of the individual formations, a combined total thickness of about 12 km can be calculated. The sequence commences with the Dwyka Tillite, a 700-m-thick diamictite unit. The overlying Ecca Group consists of "varved" rhythmitite, dark, massive, fine- to very fine-grained ultra-lithofeldspathic sandstone and subordinate mudrock with a total thickness of 2000 - 3000 m. The Beaufort Group is composed of thick mudstone layers alternating with thinner fine-grained ultra-lithofeldspathic, lithofeldspathic and lithic sandstones, with the exception of the Katberg Formation which consists largely of sandstone. Fining-upward cycles are ubiquitous, while red mudstone is com~on, especially in the upper half of the group. A maximum thickness of about 6000 m was obtained in the East London area. The Molteno Formation Consists of up to 600 m of alternating fine- to coarse-grained sublithic sandstones (frequently pebbly) and grey mudstones, generally forming finingupward cycles. The Elliot Formation (up to 500 m thick) consists of red and grey mUdstones and subordinate fine-grained lithofeldspathic sandstones arranged in fining-upward cycles. The bulk of the Clarens Sandstone consists of very fine-grained massive (occasionally cross-bedded) sandstone, with a maximum thickness of 300 m. The Drakensberg Group, consisting of up to 1200 m of basalt with some pyroclastic intercalations near the base, caps the Karoo sedimentary succession. The deposition of the Dwyka Tillite by glacier action coincided with a major change from the generally shallow marine conditions which characterised the sedimentation of the Cape Supergroup (with the source area located on the craton to the north of the basin) to a deep linear trough receiving clastic sediments from a source area situated south and south-east of the basin. The Ecca Group,the lower half of which is characterised by the presence of "proximal" turbidite sandstones, records the gradual infilling of this basin, with deltaic conditions developing in the upper part of the group in the western half of the study area (i.e. in the Waterford Formation). The overlying strata were virtually all deposited under fluviatile conditions, the chief exceptions being a stratigraphic interval within the lower half of the Beaufort Group which appears to have formed in a large body of water, a~d the aeolian Clarens Sandstone. The fluviatile sediments were all deposite1 by rivers flowin~ towards the north and nort~-west, while the Clarens Sandstone was laid down by winds blowing from the west. The Ecca and Beaufort Group sandstones are characterised by a high rock fragment content with "felsit ic" gra ins being a prc;>minent constituent. This, together with the relative abundance of quartzfeldspar porphyry pebbles in the Katberg Sandstone unit (Beaufort Group) near East London, indicates that volcanic material probably formed a prominent part of the post-Dwyka Karoo provenance.
- Full Text:
- Date Issued: 1976
- Authors: Johnson, M R
- Date: 1976
- Subjects: Sediments (Geology) -- South Africa -- Eastern Cape Geology, Stratigraphic Sedimentology
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5004 , http://hdl.handle.net/10962/d1005617
- Description: The Cape Supergroup (Sequence) comprises three groups, embracing a total of twenty-three formations, with a maximum combined thickness of approximately 8 km. The Table Mountain Group consists of medium-grained (occasionally fine- or coarse-grained), "clean", ultra-quartzose sandstone plus subordinate fine-grained, "dirty", subfeldspathic to feldspathic sandstone, mudrock, and rhythmitite. Average total thickness is about 3000 m. The Bokkeveld Group is composed of mudrock, rhythmitite and subordinate subfeldspathic to feldspathic sandstone (generally fine-grained and "dirty"), with a maximum total thickness of over 3000 m. The Witteberg Group comprises fine- to medium-grained ultra-quartzose sandstone, icaceous streaky rhythmitite, mudrock, and one thin diamictite unit; total thickness is about 1700 m. The strata belonging to the Cape Supergroup appear to have been largely deposited under marine conditions in environments ranging from outer shelf to beach. Deltaic deposits are,however, common in the upper part of the Bokkeveld Group and the Witteberg Group, while the main sandstone units in the upper third of the Table Mountain Group may have accumulated on a coastal alluvial plain. Deposition took place in a basin elongated in an east-west direction, with the palaeoslope inclined towards the south. Palaeocurrents were generally directed down the palaeoslope, but westerly 1 transport directions parallel to the palaeostrike and presumed shoreline are present in both the Table Mountain and Witteberg Groups. I The sedimentary rocks o~ the Karoo Sequence are subdivided into two groups (containing a total of eleven formations) and four ungrouped formations. Using the maximum thicknesses of the individual formations, a combined total thickness of about 12 km can be calculated. The sequence commences with the Dwyka Tillite, a 700-m-thick diamictite unit. The overlying Ecca Group consists of "varved" rhythmitite, dark, massive, fine- to very fine-grained ultra-lithofeldspathic sandstone and subordinate mudrock with a total thickness of 2000 - 3000 m. The Beaufort Group is composed of thick mudstone layers alternating with thinner fine-grained ultra-lithofeldspathic, lithofeldspathic and lithic sandstones, with the exception of the Katberg Formation which consists largely of sandstone. Fining-upward cycles are ubiquitous, while red mudstone is com~on, especially in the upper half of the group. A maximum thickness of about 6000 m was obtained in the East London area. The Molteno Formation Consists of up to 600 m of alternating fine- to coarse-grained sublithic sandstones (frequently pebbly) and grey mudstones, generally forming finingupward cycles. The Elliot Formation (up to 500 m thick) consists of red and grey mUdstones and subordinate fine-grained lithofeldspathic sandstones arranged in fining-upward cycles. The bulk of the Clarens Sandstone consists of very fine-grained massive (occasionally cross-bedded) sandstone, with a maximum thickness of 300 m. The Drakensberg Group, consisting of up to 1200 m of basalt with some pyroclastic intercalations near the base, caps the Karoo sedimentary succession. The deposition of the Dwyka Tillite by glacier action coincided with a major change from the generally shallow marine conditions which characterised the sedimentation of the Cape Supergroup (with the source area located on the craton to the north of the basin) to a deep linear trough receiving clastic sediments from a source area situated south and south-east of the basin. The Ecca Group,the lower half of which is characterised by the presence of "proximal" turbidite sandstones, records the gradual infilling of this basin, with deltaic conditions developing in the upper part of the group in the western half of the study area (i.e. in the Waterford Formation). The overlying strata were virtually all deposited under fluviatile conditions, the chief exceptions being a stratigraphic interval within the lower half of the Beaufort Group which appears to have formed in a large body of water, a~d the aeolian Clarens Sandstone. The fluviatile sediments were all deposite1 by rivers flowin~ towards the north and nort~-west, while the Clarens Sandstone was laid down by winds blowing from the west. The Ecca and Beaufort Group sandstones are characterised by a high rock fragment content with "felsit ic" gra ins being a prc;>minent constituent. This, together with the relative abundance of quartzfeldspar porphyry pebbles in the Katberg Sandstone unit (Beaufort Group) near East London, indicates that volcanic material probably formed a prominent part of the post-Dwyka Karoo provenance.
- Full Text:
- Date Issued: 1976
The Late Cenozoic history and palaeoenvironments of the coastal margin of the south-western Cape Province, South Africa
- Tankard, Anthony James Tempest
- Authors: Tankard, Anthony James Tempest
- Date: 1976
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:21068 , http://hdl.handle.net/10962/6257
- Description: This thesis examines the Late Cenozoic history and palaeoenvironments of the coastal margin between Elands Bay on the west coast and Die Kelders on the south coast. This study is introduced with a detailed discussion of eustatic sea level oscillation. The history of the existing ice sheets, sea floor spreading, isotopic composition changes of the oceans, and isostatic responses of the crust to varying loads are reviewed with regard to their bearing on sea level changes. A detailed account of the Neogene stratigraphy of the south-western Cape Province is presented. The Middle to early Late Miocene Saldanha Formation is characterised by shallow marine phosphatic sandstone and phosphorite. It is thought to have been deposited in a warm transgressive sea. The Pliocene Varswater Formation was deposited during a secondary transgression induced by.seaward tilting of the coastal margin during a time of worldwide regression. The Varswater Formation is characterised by pelletal phosphorites. It includes marine, estuarine, and fluvial facies. The estuarine sands and peats contain a rich fossil mammal fauna. Depositional environments of the Pelletal Phosphorite Member are examined by means of conventional grain size analysis to show that deposition took place on a shallow sublittoral platform dominated on the outer edge by a breaker-bar. Accretion of the breaker-bar to form a barrier-island allowed the development of an estuarine complex on the leeward side. Post-depositional diagenetic changes were examined by means of scanning electron microscopy. A detailed account of the petrology and geochemistry of the phosphorite and pelletal phosphorite is presented. The apatite mineral is a carbonate fluorapatite. It is concluded that the phosphorite is related to upwelling of phosphorus-rich waters.
- Full Text:
- Date Issued: 1976
- Authors: Tankard, Anthony James Tempest
- Date: 1976
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:21068 , http://hdl.handle.net/10962/6257
- Description: This thesis examines the Late Cenozoic history and palaeoenvironments of the coastal margin between Elands Bay on the west coast and Die Kelders on the south coast. This study is introduced with a detailed discussion of eustatic sea level oscillation. The history of the existing ice sheets, sea floor spreading, isotopic composition changes of the oceans, and isostatic responses of the crust to varying loads are reviewed with regard to their bearing on sea level changes. A detailed account of the Neogene stratigraphy of the south-western Cape Province is presented. The Middle to early Late Miocene Saldanha Formation is characterised by shallow marine phosphatic sandstone and phosphorite. It is thought to have been deposited in a warm transgressive sea. The Pliocene Varswater Formation was deposited during a secondary transgression induced by.seaward tilting of the coastal margin during a time of worldwide regression. The Varswater Formation is characterised by pelletal phosphorites. It includes marine, estuarine, and fluvial facies. The estuarine sands and peats contain a rich fossil mammal fauna. Depositional environments of the Pelletal Phosphorite Member are examined by means of conventional grain size analysis to show that deposition took place on a shallow sublittoral platform dominated on the outer edge by a breaker-bar. Accretion of the breaker-bar to form a barrier-island allowed the development of an estuarine complex on the leeward side. Post-depositional diagenetic changes were examined by means of scanning electron microscopy. A detailed account of the petrology and geochemistry of the phosphorite and pelletal phosphorite is presented. The apatite mineral is a carbonate fluorapatite. It is concluded that the phosphorite is related to upwelling of phosphorus-rich waters.
- Full Text:
- Date Issued: 1976
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