Academic literature on the topic 'Sediment hopper'

Thesis (MSc)--University of Stellenbosch, 1989.<br>AFRIKAANSE OPSOMMING: Senosoiese sedimente langs die suidooskus van die Kaapprovinsie is periodiek deur verskeie outeurs vir meer as 'n eeu bestudeer. In hierdie aanbieding word die Iiteratuur saamgevat en vele dubbelsinnige stratigrafiese onderverdelings en definisies opgeklaar. Die Senosoiese afsettings kan volgens oorsprong geklassifiseer word as marien, eolies en fluviaal. Die mariene afsettings, synde strand-, nabystrand-, estuarien of lagunale afsettings geassosieerd met transgressiewe/ regressiewe kusIyne, word nou op grond van kenmerkende litologiese, paleontologiese sowel as ouderdomsverskille onderverdeel in die Paleogeen Bathurst, Neogeen Alexandria en Kwaternere Salnova Foraasies. Die Laat-Plioseen tot Vroeg-Pleistoseen Nanaga Formasie, Middel- tot Laat- Pleistoseen Nahoon Formasie en die Holoseen Schel• Hoek Formasie vorm die kus-eoliese afsettings. AI die mariene en marienverwante (eoliese} formasies, gekenmerk deur kalkige klastiese afsettings, is saamgegroepeer in 'n nuutgedefinieerde Algoa Groep. Fluviale afsettings word onderverdeel in die Martindale, Kinkelbos, Bluewater Bay, Kudus Kloof en Sunland Formasies. Die onderskeie afsettings word gekorreleer met verskillende seevlakstande deur geologiese tye. Die vroegste Senosoiese transgressiewe/regressiewe siklus het in die Vroeg-Paleoseen begin en die hoogste aangetekende elevasie vir die era bereik. Die Bathurst Formasie is waarskynlik gedurende hierdie regressie afgeset. 'n Tweed~ kleiner transgressie/ regressiesiklus het plaasgevind gedurende die Laat-Eoseen tot Vroeg-Oligoseen. Sover tans bekend, kan geen afsetting in die dagsoomgebied van die Algoa Groep definitief met hierdie siklus in verband gebring word nie. Die volgende siklus, wat 'n transgressiewe maksimum van c. 250 m bereik het, het begin in die Middel-Mioseen en verstryk in die Vroee Plioseen. Mariene planasie van die kusplatform het gedurende die transgressie plaasgevind terwyl die Alexandria Formasie wat tans bo 120 m geleë is, gedurende die regressie afgeset is. Die Vroeg-Plioseen transgressie het waarskynlik 'n maksimum huidige hoogte van c. 120 m bereik, waartydens o.a. die 120 m branderstoep en "Humansdorpterras" gekerf is. Die Alexandria Formasie tans geleë tussen 60 en 120 m, is afgeset gedurende die Laat-Plioseen regressie. Hierdie regressie het verskeie relatief lang stilstande, wat waarskynlik die 106-m, 90- tot 100-m en 84-m branderstoepe verklaar, ondervind. Selfs die 60-m en 52-m kuslyne kon tydens hierdie regressie gevorm het. Voorlopige paleontologiese getuienis dui egter daarop dat die 60-m kuslyn 'n transgressiewe maksimum van 'n daaropvolgende siklus verteenwoordig, gevolg deur 'n regressie met minstens een beduidende stilstand by 52 m. Die Alexandria Formasie geleë tussen c. 60 en 30 m, is waarskynlik gedurende hierdie regressie gedeponeer, waartydens ook die Bluewater Bay, Kinkelbos en Kudus Kloof Formasies afgeset is. Gedurende die Kwaternêre transgressie/regressiesiklusse, waarvan minstens vier aangedui word, is die Salnova Formasie (afwesig bo 30 m) afgeset. Die Nahoon Formasie, wat ook op groot skaal op die kontinentale bank ontwikkel is, is gedeponeer gedurende die laaste twee Pleistoseen glasiale toe seevlakke tot benede -100 m gedaal het. Die Schelm Hoek Formasie wat tans nog afgeset word, het ontstaan uit die transgressiewe maksimum van die Flandriese transgressie aan die begin van die Holoseen.<br>ENGLISH ABSTRACT: Cenozoic sediments along the south-east coast of the Cape Province have been studied intermittently for more than a century by various authors. In this presentation the literature is reviewed and many ambiguous stratigraphic subdivisions and definitions are clarified. The Cenozoic deposits can be classified, according to origin, as marine, aeolian and fluvial. The marine deposits, being lagoonal deposits either beach, nearshore, estuarine or associated with transgressive/regressive shorelines, are now subdivided on the grounds of distinct lithological, palaeontological as well as age differences into the Palaeogene Bathurst, Neogene Alexandria and Quaternary Salnova Formations. The Late Pliocene to Early Pleistocene Nanaga Formation, the Hiddle to Late Pleistocene Nahoon Formation and the Holocene Schelm Hoek Formation constitute the coastal and marine-related aeolian deposits. All the marine (aeolian) formations, which are characterised by calcareous clastics, have been grouped together in a newly defined Algoa Group. Fluvial deposits are subdivided into the Martindale, Kinkelbos, Bluewater Bay, Kudus Kloof and Sunland Formations. The various deposits are correlated with different stands of sea-level through geological time. The earliest Cenozoic transgression/regression cycle started in the Early Palaeocene and reached the highest recorded altitude for the era. The Bathurst Formation was probably deposited during this regression. A second lesser transgression/regression cycle occurred in the Late Eocene to Early Oligocene. As far as is presently known, no deposit in the outcrop area of the Algoa Group can be definitely related to this cycle. The next cycle, which reached a transgressive maximum of c. 250 m, started in the Middle Miocene and terminated in the Early Pliocene. Marine planation of the coastal platform took place during the transgression, whilst the Alexandria Formation presently situated above 120 m, was deposited during the regression. The Early Pliocene transgression is considered to have reached a maximum present-day elevation of c. 120 m, during which the 120 m marine bench and "Humansdorp Terrace", amongst others, were carved. The Alexandria Formation presently situated between 60 and 120 m, was deposited during the Late Pliocene regression, which experienced several relatively long stillstands which probably account for the 106 m, 90 t.o 100 m and 8.4 m benches. Even the 60 m- and 52 m-shorelines could have been formed during this regression. Preliminary palaeontological evidence, however, suggests that the 60 m shoreline represents a transgressive maximum of a subsequent cycle followed by a regression with at least one significant stillstand at 52 m. The Alexandria Formation situated between c. 60 and 30 m, was probably deposited during this regression, which also saw the deposition of the Bluewater Bay, Kinkelbos and Kudus Kloof Formations. During the Quaternary transgression/regression cycles, of which at least four are indicated, the Salnova Formation (absent above 30 m) was deposited. The Nahoon Formation, which is also extensively developed on the continental shelf, was deposited during the last two Pleistocene glacials, when sea-levels receded to less than -100 m. The Schelm Hoek Formation, which is still being deposited, originated from the transgressive maximum of the Flandrian transgression at the start of the Holocene.

There is a high potential for economic gold deposits in the Slave Structural Province, NWT. Gold exploration, however, is hampered by a complex cover of Quaternary sediments and limited bedrock outcrops. Furthermore, there is a lack of information on the glacial dispersion of gold and the effects, if any, of postglacial redistribution of gold under prevailing periglacial conditions. Therefore, the partitioning of gold among size and density fractions was determined for the various surficial materials in the vicinity of, and down-ice from, known gold mineralization in the southeastern portion of the Hope Bay Greenstone Belt, 650 km northeast of Yellowknife, NWT. Terrain mapping by Ryder (1992) identified several types of surficial materials consisting of weathered rock, till, marine sediments and mixtures of the different types. Soil and humus samples were collected from thirty-seven pits along five lines on the Wally Grid. The lowermost horizons from each pit, and A and B horizons from selected soil pits, were wet sieved into four size fractions between 2000 um and 212 um; the resulting -212 um fraction was analyzed for gold by fire assay-atomic absorption spectroscopy (FA-AAS). Samples from one grid line were further sieved to obtain the -53 um fraction which was analyzed for gold by FA-AAS. LFH horizons and bog samples were milled to -1000 um and organic-rich soils (Ah and O lenses) were dry sieved to -70 um, and were analyzed for gold by neutron activation analysis. Regional till samples down-ice from known mineralization were wet sieved into six size fractions. The -53 um fraction and light and heavy mineral separates of the - 212+106 um and -106+53 um fractions were analyzed for gold by FA-AAS. The -53 um fraction was analyzed for gold by aqua regia column-inductively coupled plasma spectrometry (AR column-ICP). Two distinct types of geochemical anomalies were identified in the study area: (i) an older gold anomaly in regional till, and (ii) a younger gold anomaly in locally-derived materials. Gold results of heavy mineral concentrates (HMC) of the -106+53 um fraction and the silt-clay (-53 um) fraction of regional till identified an anomalous gold zone that is detected for at least 2 km down-ice. Although the contrast and gold concentrations in the silt-clay are lower, the -53 um fraction of regional till contains over 60% of the gold with most of the balance residing in the -106+53 um HMC fraction. For the younger anomaly, gold concentrations in soil profiles decrease from the upper A and B horizons to lower C horizons. Exceptions occur, however, for horizons directly overlying mineralized bedrock; in these cases, gold values increase with depth. In cross section, anomalous gold zones have a 'mushroom-shaped' vertical distribution pattern in which the anomalous zone defined by the near-surface horizons is 10 to 50 m broader than the anomaly in the underlying horizons. Gold values from weathered rock are typically 10x to 100x greater than from other surficial materials as they contain a high proportion of weathered, local bedrock fragments. Results show there is no systematic variation of gold values across the surface of individual frost boils developed in these weathered rock materials. For reconnaissance scale exploration, a 500 g sample of -2 mm field material should be collected from the central portion of regional till frost boils. A 50 g subsample of the -53 um fraction should be analyzed for gold by a reliable analytical method having a low detection limit for gold. Considering the width and length of the gold dispersal train, a rectangular sampling grid should be utilized whereby grid lines oriented perpendicular to ice flow direction are spaced 500 m apart and samples collected every 40 m. As a complement to gold results from the -53 um fraction, a large, 2 to 5 kg field sample could be used to analyze the -106+53 um HMC fraction for gold. Costs would increase but would be worthwhile to provide an extra degree of assurance in identifying gold anomalies. For property scale exploration, a representative 30 g subsample of the -53 urn fraction could be analyzed by FA-AAS. However, although the -53 um fraction contains over 75% of the gold for the local materials, sample representativity is only slightly reduced if a 30 g subsample of the -212 um fraction is analyzed for gold. In most cases, a 500 g field sample of -2 mm material should initially be collected at 10 to 20 m spacings along grid lines 100 m apart. Infill sampling lines should be spaced at 50 m. It appears that marine sediments blanket geochemical anomalies but additional research is needed to address this problem, and to suggest a possible geochemical method that could be used in these areas.