Call number: LD2668 .T4 1963 S674 / Master of Science

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Until recently, there has been very limited academic palynological study of South Africa’s offshore west coast Cretaceous sequences. For this thesis, an in-depth study of the palynological sequence as well as a combination of other disciplines was undertaken for Offshore Sites C-B1 and O-A1, situated off the west coast of Cape Town. The study has yielded copius amounts of mostly well-preserved palynomorphs (trilete spores, pollen, diniflagellate cysts and foraminiferal test linings) ranging from Early to Late Cretaceous in age. Both Offshore Sites consist mostly of sandstone and siltstone lithologies but it was the carbonaceous mudstone-rich intervals that were targeted for palynomorph extraction. The Petroleum Agency, SA (previously SOEKOR) has identified ten time periods (nine in the Cretaceous and one in the Tertiary) from these lithologies but for this study, only eight of these time periods that span the Barremian to the Campanian stages of the Cretaceous were utilized.. Over 550 samples that include cuttings, sidewall and core samples, have been provided by the Petroleum Agency, SA representing offshore Cretaceous sedimentary strata from the west coast of South Africa. All of these samples have been analysed palynologically. A wide variety of palynomorphs have been described from these samples and are fully illustrated. These include angiosperms, gymnosperms, spores of known and unknown botanical affinity, four species of algae and one species of fungi. These palynomorphs are compared with published descriptions and illustrations to aid and effect identifications. Several new palynomorphs were found, however formal naming will only be undertaken at a later stage. Palynological data indicates that the gymnosperms and ferns dominated the plant groups during both the Early and Late Cretaceous intervals of both Offshore Sites. Angiosperms only really became a significant part of the vegetation during the Late Cretaceous. Gymnosperms found at both Offshore Sites are dominated by the genera Classopollis, Podocarpidites, Zonalapollenites, Balmeiopsis and Exesipollenites. Cyathedites, Gleicheniidites and other trilete schizeaceous types dominated the spore population. The information gained from the identification of the microfossils present in these two Offshore Sites contributes not only to amplifying the biostratigraphy of this part of the geologic column but also to reconstruct the Cretaceous palaeoflora and palaeo-environment. The age ranges of the palynomorphs present have provided a general Cretaceous age bracket for these two Offshore Sites, supporting the Petroleum SA’s findings. However these palynomorphs do not always age-define the level they were found in and on more than one occasion Tertiary palynomorphs were located at the base of the Cenomanian and Turonian stages (Late Cretaceous Period). The pollen and spore assemblage include many species that are known from both northern and southern hemispheres, although the northern hemisphere representatives are usually represented by only a few individuals. There is a noticeable difference between the Early and Late Cretaceous floras. Early Cretaceous floras are dominated by gymnosperms and fern spores with only a few angiosperm pollen grains present. Late Cretaceous flora is much richer in angiosperm pollen and in Tertiary flora. Botanical affinities were used to reconstruct the palaeoflora of both Offshore Sites. The forests that existed during the Cretaceous were probably cool, moist and temperate, located in the highlands of a slowly developing rift valley. The dominant trees in these forests produced palynomorphs attributable to Podocarpaceae, Microcachryidites, Balmeiopsis and Exesipollenites. The lowland woodlands consisted primarily of cheirolepideacean conifers with the undergrowth including varieties of ferns and bryophytes. Results of the pollen and spore analysis suggest that neither west coast sites fits into any established pollen zonation. Therefore new pollen zones were established for this thesis and will hopefully contribute to the understanding of the palaeoflora of this part of the southern hemisphere. Zones are used to designate each Offshore Site into divisions that characterize the essential changes in the vegetational history as well as divide the history of the palaeoflora in the Cape Basin. Offshore Site C-B1 consists of 5 zones (CI, CII, CIII, CIV and CV) and four subzones namely Subzone CI-A, CI-B, CV–A & CV–B. Offshore Site O-A1 is comprised of 5 zones namely OI, OII, OIII, OIV and OV. Palaeoenvironmental reconstructions were deduced by studying the palaeoflora and palynodebris in each zone / facies of each Offshore Site. The Early Cretaceous was tropical, humid and warm with palaeoflora indicators such as Classopollis and Ephedripites suggesting the start of a shift towards warmer more semi-arid conditions. In comparison, the beginning of the Late Cretaceous assemblages suggested a shift to hotter, humid and then semi arid conditions. By the end of the Late Cretaceous the environment had once again reverted back to warm, wet and humid conditions. Using the core depth as scale, the relative frequencies of the organic matter types in Offshore Sites C-B1 and O-A1 were plotted using CONISS – the distance cluster analysis program which identified four main groups of samples in each core (Facies CB- D1 to D4 and OA – D1 to D4) on the basis of their organic content. These eight palynofacies assemblages (Facies CB- D1 to D4 and OA – D1 to D4) show the gradual and immediate changes in palynodebris and could reflect environmental and geological changes. The palynodebris component for both Offshore Sites supports the origin of the sediments deposited into the Cape Basin as continent-derived and transported into the Cape Basin via fresh water sources. The presence of sporomorphs and resins in the palynodebris reflects a great diversity of hinterland vegetation. Plant and cuticle palynodebris found at both Offshore Sites suggest stable dry conditions terrestrially and near shore deposition. Amorphous organic material and the presence of green algae throughout both Offshore Sites indicate a terrigenous source associated with shallow fresh to brackish water of lagoons and swamps. The presence of marine palynomorphs supports deposition in a marine or saline esturine marsh environment.

The Arctic is climatically sensitive to global change and therefore climate records from this region are of key importance. Little, however, is known of the state of the Arctic in the traditionally “greenhouse” period of the Cretaceous. Climate conditions are often assumed to have been warm-temperate as evidenced by the presence of conifers and dinosaur trackways on Svalbard and other Arctic localities. However, isotopic evidence for cooling episodes, sequence stratigraphic evidence for interpreted glacio-eustatic sea-level falls, and the presence of more enigmatic deposits such as dropstones and glendonites has led to a re-evaluation of the question of climatic dynamism during the Cretaceous. This project evaluates the climatic and environmental character of Arctic Svalbard during the Early Cretaceous (palaeo-latitude of c. 65 °N), via a multiproxy sedimentological, geochemical, sequence- and chemo- stratigraphic study of Berriasian–Albian strata from the Central Basin of Svalbard. The “outsized clasts” recorded on Spitsbergen do not show evidence that they were rafted by glacial ice (e.g. surface striations), although could have been rafted by seasonal sea-ice. The results show that regionally widespread cold water conditions were the most likely control on ikaite formation and glendonite preservation. This counters recent studies that suggest a methane-seep driver for Mesozoic glendonites, and supports the global extent of Valanginian to Hauterivian and Late Aptian global cooling. Surface temperatures during cool episodes of < 14 °C, as implied by the presence of glendonites at the seafloor, are consistent with Polar (90 °N) temperatures being below freezing (even given reduced pole-to-equator temperature gradients). This study therefore supports the hypothesis that small polar ice-caps developed during the Valanginian – Hauterivian and Late Aptian cooling events.

The St. Lawrence Platform is located along the northern shoreline of Lake Ontario, currently in an intra-cratonic setting exposing relatively flat-lying middle Ordovician sedimentary strata. The purpose of this study is to gain insight on recent brittle deformation events that have deformed the bedrock. Based on structural field observations, broadly trending E-W extensional joints are the youngest stress recorded in the bedrock. These joints are partially filled and sealed with calcite mineralization and were strategically sampled to gain insight on the source and timing of fluid flow. Trace element geochemistry and stable isotope (δ18O and δ13C) analysis on calcite mineralization indicate that their compositions are analogous to the host rock, thus, fluids originate from connate fluids that were released from pore space during deformation. In addition, U-Pb geochronology via LA-ICP-MS methods yield a model age of 101 ± 6 Ma (MSWD: 2.3). The date of calcite crystallization is contemporaneous with the establishment of North America’s modern compressive stress field, and is linked to a Cretaceous tectonic plate reorganization event that was global in scale. This study demonstrates that calcite veins can serve as a tool to date brittle deformation in limestone, which could have direct applications in hydrocarbon exploration, paleohydrology, and the consideration for locating sites to host deep geological repositories.

The estuarine to fluvial sediments of the mid-Cretaceous (Late Albian/Early Cenomanian) Dakota Formation of Jefferson Co., Nebraska (NE) and Washington Co., Kansas (KS) were deposited in a marginal marine setting along the eastern margin of the Cretaceous Western Interior Seaway. Three depositional facies based on various lithic content are recognized in the study area: Facies 1: Fluvial Channel Facies, Facies 2: Paleosol/Interfluve Facies, and Facies 3: Bay Head Delta/Estuarine Facies. The facies interpretation helped confirm that the Dakota Formation was deposited in a marginal marine setting in which low-gradient fluvial systems supplied a wave-dominated, estuary system. Petrographic analysis of the Fluvial Channel Facies concluded that the sandstones can be classified as quartz-rich lithic arkose. These findings differ slightly from previous studies on Cenomanian Dakota Formation strata in Thurston Co., NE. Palynostratigraphic, subsurface, and sedimentologic evidence helped to delineate a more accurate sequence stratigraphic framework for the Dakota Formation in the study area. Three large-scale, unconformity-bounded, sequences (D0, D1, and D2) are recognized, within which deposits of the transgressive and falling stage systems tracts are preserved in the Dakota Formation in the study area. While no physical deposits exist for the falling stage and lowstand systems tracts, evidence for their past occurrence can be observed by the erosional nature of the sequence boundaries. Detailed analysis of the systems tracts framework allows delineation of a generalized sea-level curve for the Dakota Formation in the study area. Analysis of the sequence stratigraphic framework revealed a Late Albian/Early Cenomanian sea-level fall that subsequently created valley incisions of over 25 m into the Late Albian D1 sequence. A careful literature review combined with sequence stratigraphic evidence suggests that a geologically fast-acting eustatic sea-level mechanism lowered worldwide sea-levels by more than 25 m from Late Albian into Early Cenomanian time. A reevaluation of the mid-Cretaceous "greenhouse" world suggests that a glacioeustatic component to the observed sea-level changes may have occurred. A Southern Hemispheric polar ice sheet with limited extent and volume compared to "icehouse" continental ice sheets, along with global alpine glaciers fed by wet climate cycles are hypothesized to account for sea-level fluctuations that resulted in valley incision and subsequent filling in the study area.

Includes other papers published by the author. Bibliography: p. 620-629.

Oceanic circulation remains one of the poorly understood elements of the global climate system, despite its importance to planetary heat redistribution and carbon cycling. The nature of deep-water formation and circulation in ancient oceans are even more poorly constrained. In order to understand climate dynamics of past and future climates we must have a better understanding of the role of deep-ocean circulation. In this dissertation I investigated changes in intermediate- to deep-water circulation in three different ocean basins during two different geologic eras. The first study focused on the late Pleistocene (~25 ? 60 ka) California margin to investigate the role of intermediate water circulation in abrupt climate fluctuations. The other two studies investigated deep-water circulation during the Late Cretaceous (~70 ? 100 Ma) greenhouse interval, to determine if deep waters formed in the southern Indian or Atlantic basins. The above studies employed neodymium isotopes preserved in biogenic apatite (fish teeth and bones) and foraminiferal calcite to reconstruct the provenance of intermediate- to deep-water masses. Here I present data from two sites located at intermediate depths on the late Pleistocene California margin as well as seven Deep Sea Drilling Project and Ocean Drilling Program Cretaceous aged sites; four in the South Atlantic Ocean, and three in the Indian Ocean. The new Pleistocene data rule out changes in the source of intermediate waters to the California margin, thus the recorded changes in seafloor oxygenation were caused by changes in sea surface productivity. In the Cretaceous, the spread of deep waters formed in the high-latitude South Atlantic was hindered by tectonic barriers until the mid Campanian when the subduction of Rio Grande Rise allowed for the continuous flow of deep waters from the Southern Ocean into the North Atlantic. The deep Cretaceous Indian Ocean was filled with deep waters formed in the high-latitude Indian Ocean, until being replaced with waters sourced in the Pacific from the late Cenomanian to early Campanian before a return to southern Indian-sourced waters for the remainder of the study interval.