The Re-Os organic-rich sedimentary rocks (ORS) geochronometer has the potential to provide precise depositional ages and vital information on the Os isotope composition of palaeo-seawater. This thesis presents new geochronology data from Proterozoic sedimentary successions and insights into Re-Os systematics of organic-rich sedimentary rocks and petroleum products such as bitumen and oil. New Re-Os ORS geochronology from two drill cores indicate that the Proterozoic Atar Group of the Taoudeni basin, Mauritania is ~200 Ma older than previous estimates (1107 ± 12 Ma, 1109 ± 22 Ma and 1105 ± 37 Ma). Furthermore, this data also provides precise Re-Os geochronology data from sedimentary rocks that have experienced flash pyrolysis and demonstrate that the Re-Os systematics are not disturbed by the effects of very rapid heating. Coupled with palaeomagnetic data the Re-Os geochronology suggests that a reassessment of the role of the West African craton during the assembly of Rodinia is required. New Re-Os geochronology for the Ballachulish Slate Formation of the Dalradian Supergroup, Scotland yields a depositional age of 659.6 ± 9.6 Ma. The Re-Os age represents a maximum age for the glaciogenic Port Askaig Formation and represents the first successful application of the Re-Os geochronometer in sedimentary rocks with low Re and Os abundances (<1 ppb and <50 ppt, respectively). This new age suggests that the Port Askaig Formation may be correlative with Sturtian glaciations rather than middle Cryogenian events. Laboratory-based hydrous pyrolysis experiments were employed to evaluate the complexation of Re and Os in ORS and their transfer behaviour into petroleum. The findings from these experiments demonstrate that the Re-Os geochronometer is not disturbed by thermal maturation of whole rocks. Furthermore, the data support the hypothesis that the isotope composition of oils and bitumens can be used to fingerprint petroleum to specific source rocks.

The late Neogene to Quaternary of Cyprus is considered to be a tectonically active period coeval with major climatic change. Uplift, associated with the activities of the supra-subduction zone to south of island was concomitant with global cooling, the expansion of the Northern Hemisphere Ice Sheets and the Middle Pleistocene Transition. Despite the globally significant climatic events during the period of deposition, the Plio-Pleistocene climatic record in Cyprus is largely unknown and for the most part ignored. The objective of this study was therefore to investigate the stratigraphical record of the ‘fore-arc’, with the intention of elucidating the mechanisms controlling the cyclicity on sedimentation, in an attempt to understand the uplift history. Sequence stratigraphical, palaeohydraulic, micropalaeontological and architectural analyses were conducted to provide an understanding of the sedimentary cyclicity, at key stratigraphical intervals. Correlation of the results to global patterns provided a robust method for deducing climatic controls on sedimentary deposition, thus leaving the residual record of tectonic uplift. Cyprus is critically located in a region sensitive to climatic perturbations and is positioned between two major oscillatory atmospheric cells (Hadley and Ferrel Cells). The position of the boundaries of these cells is governed by the Inter Tropical Convergence Zone, which is controlled by latitudinal temperature gradients and ice volume. The effect of the Northern Hemisphere Ice Sheets and its influence on the climate belts over the eastern Mediterranean has been examined and has allowed the recognition of distinct climatic and oceanographic conditions. The results indicate that the sedimentary evolution of the Cyprus ‘fore-arc’ responded to the progressive development of the Northern Hemisphere Ice Sheets and the orbitally controlled meridional movements of the Inter Tropical Convergence Zone. Tectonics created the relief and source necessary for deposition, whilst climate provided the overriding control on internal architecture within the depositional systems.

No description available.

A description of the Devonian goniatites and their localities in Devon and Cornwall is given based upon museum material and new collecting. This enables correlation with the established continental successions and the following German ammonoid faunas have been recognized. The fauna of the Anarcestes Stufe has been recognized in South Devon and probably in Cornwall. Two faunal subdivisions of the Maenioceras Stufe have been recognized, the lowest only at Wolborough, South Devon, the uppermost at Lummaton and Barton, Devon and Trevone and Portquin, North Cornwall (the last two localities have previously been identified with the Cheiloceras Stufe). The three German zones of the Frasnian have been identified in South Devon but only the middle one with certainty in North Cornwall. The Famennian ammonoids have not been exhaustively examined. Only Maenioceras Stufe goniatites occur in the massive lime stones of South Devon which appear to be wholly Givetian in age ; no Frasnian goniatites occur within them but they are found in the thin-bedded or rubbly limestones immediately above. The absence of evidence for the Cheiloceras Stufe emphasises the widespread development of ostracod-slate facies at that time. The recognition of the Gattendorfia and Wocklumeria Stufen (largely the work of others) tells against the large unconformity usually supposed to mark the base of the Carboniferous in South-West England. Ontogenetical details are given for several species: the evidence from Maenioceras shows that it probably evolved direct from Anarcestes or early Wemeroceras. Peculiar internal growths on specimens of Sobolewia shed light on the relation of the soft parts to the shell in goniatites.

Detailed mapping of the Carboniferous strata of Yoredale facias in north Westmorland has shown that the Middle Limestone Group succession comprises nine well developed cyclothems. The major limestones at their bases are clearly recognisable throughout the region but thin calcareous horizons, found within the clastic successions of four of the earliest cycles, are of more local distribution. Correlations of the limestones with those in the Westmorland Pennines are suggested and involve the equation of the Iron Post Limestone with the siliceous upper leaf of the Newby Mill (= Four Fathom) Limestone. The Upper Limestone Group sediments, lacking well marked calcareous horizons, cannot satisfactorily be divided into cyclothems. However, high in the sequence, the Bewley Castle Limestone has been shown to represent marine strata in the Crag Limestone cyclothem of the Pennines. A decrease in the thickness of the Middle Limestone Group strata, of the order of 10%, has been detected in the western parts of the area as compared to the region east of the Lyvennet. This is consistent with the regional picture of minimal subsidence in west Cumberland and, taken in conjunction with the close similarity in the successions on either side of the Pennine Faults, it indicates that, at this time, a large paxt of northern England behaved as a distinct tectonic unit. In comparison with the rapidly subsiding trough to the north this was a stable region, to the whole of which the term 'Alston Block' may usefully be extended. Its structural unity was broken only after Carboniferous deposition ceased, by the initiation of the Pennine Faults; there is evidence that the latter had no earlier history as hinge-lines affecting deposition. Of particular mineralogical interest are the Grayber Limestone, the upper leaf of which invariably is rich in glauconite, and the argillites which, irrespective of their position in the cycle, have kaolinite as a common component. This is a product of diagenesis and is believed to be due to the deep penetration of weathering under the tropical conditions of immediately post-Carboniferous times. A comparison between pale and dark limestones suggests that finely divided pyrite has a greater influence upon colour than does organic carbon. Little mineralogical variation is present through the major limestones but certain trace elements, most notably manganese and strontium, are present in greatly varying amounts. Manganese is closely associated with iron- and magnesium-bearing carbonates and may total 1% in some dolomitised limestones. Studies of strontium variation in the Little Strickland Limestone strongly suggest that its distribution reflects primary differences in the proportions of aragonite and calcite accumulating on the sea floor. Such variation may prove to be a useful tool in aiding the understanding of the micro-environments of limestone deposition. Chemical and mineralogical data support stratigraphical evidence which indicates that the bulk of the succession was laid down in relatively quiet shallow marine waters whose salinity varied from normal during times of limestone deposition to brackish at higher levels in most of the cycles. Only occasionally, where there is a sheet sandstone with a sharply erosional base, may a fluvial environment be said to have been dominant. A widespread tectonic control, probably depending ultimately upon isostatic forces, is considered to be the basic cause of the cyclic repetition. Uplift in post-Carboniferous times led to strong erosion under a tropical climate which became increasingly arid. Its effects remain clearly recognisable in the reddening of the Carboniferous rocks which may extend to a depth of as much as 1000 feet below the New Red Sandstone unconformity. Two stages of reddening have been recognised; they were separated by a period of local dolomitisation consequent upon the extension into the Vale of Eden of the Zechstein Sea. It is postulated that the Vale underwent rapid sinlcing during the time of accumulation of the New Red Sandstone and that thick deposits did not spread far beyond their present limits. Deep wadi-like channels with a general northerly trend have been recognised and, in the vicinity of Appleby, upstanding remnants of Carboniferous strata, isolated by erosion from the main upland mass, can be proved to exist. The conclusion that this main erosion area lay to the south and west is supported by facies. changes in the basal New Red Sandstone, Brockram giving way to pebbly Penrith Sandstone in a northerly and easterly direction.

No description available.

Yoredale type cyclothems of the Mid-Carboniferous of north east England were deposited as a result of glacio-eustatic fluctuations arising from waxing and waning of the Gondwana ice sheets present in the southern hemisphere. Rhythmic alternations of areas of maximum cyclothem thickness have been recognised in the Scar to Little Cyclothems which are attributed to localised differential subsidence, flexuring and uplift of the Alston Block of the northern Pennines. A detailed study of one cyclothem, the Great Limestone Cyclothem of the Alston Block, reveals that within the transgressive carbonates, the beds form two and a half thinning-upward to thickening-upward bed-sets with the individual beds and the bed-sets being correlatable across the region. Inevitable diagenetic alteration of the Great limestone has occurred and resulted in resetting of some initial geochemical values. However, it is proposed that in the case of δ18O and several trace elements their trends through the limestone do in fact track an original pattern, namely that of the bed-thickness pattern. It is suggested here that the cyclothems are attributable to the short eccentricity Milankovitch rhythm, the bed-sets, within the Great Limestone, to the range of either the obliquity and precession rhythms, with the beds in the Great Limestone being deposited in periods of the sub-Milankovitch millennial time-scales. The biostromes within the Great Limestone, the Chaetetes band, Brunton band and the Frosterly band are typical of shallow-marine environments as are all grains seen in thin-section analysis. All limestone beds are a similar bioclastic wackestone to packstone with no observable changes in the proportions of the various elements throughout the thickness of the Great Limestone.

In northern South America, Upper Palaeozoic strata were deposited extensively over peri-cratonic areas associated with restricted seas located between Laurentia and Gondwana, in equatorial Pangea. In many places the successions are rarely exposed, and so are poorly documented; this is largely the result of extensive weathering and dense vegetation in the tropical Andes. However, these strata do contain significant information for palaeogeographic and palaeoclimatic reconstructions, and our understanding of the evolution of northern Gondwana and the finally assembly of Pangea. The main objective of this thesis is the study of Permian carbonates in the Venezuelan Andes, their sedimentology, geochemistry, diagenesis and petroleum potential. The Palmarito sediments were deposited on a carbonate ramp that dipped basinwards towards the north facing the open ocean. The formation evolved from the underlying fluvial (Sabaneta Formation) through tidal-flat to mid-outer ramp deposits, with all facies recording a well-developed cyclicity. These strata fill an important gap in the regional palaeogeography and hence have revealed important implications for the palaeoclimate and palaeoceanography of the time. The results of this study of Palmarito strata have significant implications for the palaeogeography of this Permian time. From the facies analysis of the Palmarito Formation, new evidence has been provided for a central Pangean seaway. Furthermore, isotope analyses have improved the time-frame for the succession from 87/86Sr data, and in addition, the long-term stratigraphic trends in the δ13C and δ18O data have permitted interpretations of the climatic and oceanographic controls on Permian carbonate deposition. Moreover, metre-scale cyclicity shows the patterns of short-term controls on sedimentation, where autocyclic and allocyclic processes affected deposition and the vertical stacking of facies. An analysis of the diagenesis of the Palmarito carbonates shows several stages of cementation and alteration, although the strata are mainly fine-grained and coarse cements are rare. Finally the elements of the petroleum system for the Palmarito have been considered for the succession and as a result, it can be proposed that, firstly, fractures in finer-grained facies have the potential to provide reservoir rocks, and secondly, that although high values of Tmax have been obtained from rock-eval analysis from one locality, Palmarito strata do have the potential to form source rocks. Further investigation is required to ascertain the actual hydrocarbon potential of the Palmarito. The high content of finer-grained facies with low permeability provides the Palmarito strata a high potential to perform as a seal, as well as possibility to develop stratigraphic traps.

The Pleistocene – Present-day sedimentary succession of the South Caspian Basin was deposited syntectonically alongside growing anticlines in an under-filled, rapidly subsiding basin. The combination of ample sediment supply from surrounding mountain belts, fast sedimentation rates (variously estimated at between 0.4 and 1.7 m/kyr) and high accommodation space has resulted in an exceptionally thick succession (up to 3000 m) which documents structural growth and regional tectonics at a high temporal resolution. The succession additionally records the palaeo-water level history of the Caspian Sea —an internally drained lake— which has fluctuated at much higher magnitudes and frequencies throughout the study interval than along comparable marine settings. The Pleistocene – Present-day Caspian stratigraphy therefore represents an ideal geological dataset with which to study depositional processes along syntectonic fold ‘growth strata’ and to investigate the relative impacts of tectonics and climate change on syntectonic sedimentation. This thesis presents three studies which describe South Caspian Basin fold growth strata at a variety of scales using offshore seismic data from the north-eastern portion basin and field data from western Azerbaijan. The studies examine; [1] the vertical spacing and regionally lateral synchronicity of angular unconformities within late Pliocene – Present-day growth strata; [2] Pleistocene basin margin syntectonic sedimentology, and: [3] the process of large scale slope failure from submarine landslide deposits along folds located in the basin interior. The results of these studies add to the scientific understanding of the regional geology and of tectono- sedimentary processes in general. However the main finding —recurrent in all three studies— is the presence of repetitive sedimentary patterns and correlations. These are suggested to represent orbital Milankovic cycles of 40,000 years (obliquity) and 100,000 years (eccentricity). Orbitally driven climate change appears to have been a major control on South Caspian fold growth strata architecture and sedimentary processes within anticline mini- basins. Fold growth effects are also observed but these are relatively subdued as tectonic uplift was outpaced by high sedimentation rates.

The following succession of Tertiary rocks is established on the Maltese island of Gozo (youngest beds first): Upper Coralline Limestone, over 290 feet; Transitional Greensand, 0 to 40 feet J Blue Clay, 0 to 200 feet; Upper Globigerina Limestone, 40 to l10-feet; Middle Globigerina Limestone, 0 to 60 feet; Lower Globigerina Limestone, 17 to 75 feet; Scutella Bed, ½ to 20 feet; Lower Coralline Limestone, over 450 feet. The algal and foraminiferal Lower Coralline Limestone was probably deposited in shallow water. The prominent Scutella Bed resembles a near-surface shell bank. Two phosphatic nodule beds, possibly marking stagnant periods, separate the Globigerina Limestones. The lower and upper divisions are formed of pelagic foraminifera with lamellibranchs and neritic echinoids. The middle division, a marly limestone, may be a deep of water deposit but has an upper, coarser facies in south-west Gozo. The Lower and Middle Globigerina Limestones thin eastward and the latter is absent over much of the eastern area where the nodule beds coalesce. The Upper Globigerina Limestone— Blue Clay boundary, despite sane previous opinions, is always sharp. The two beds have faunal similarities, their lithological differences are probably caused by a sudden onset of mud deposition. Variations in, thickness of the Blue Clay are considered to have an erosional origin. There is a gradual passage through the glauconitic Transitional Greensand, which varies in thickness and lithology and has a thick-shelled fauna suggesting a shallow water origin, to the Upper Coralline Limestone, which has a soft, lower division and a hard upper one, complicated by lateral variation and later recementation. The echinoids from the above succession are listed and the following ten species are described and figured: Scutella subrotunda, Scutella sp. nov., Hemiaster scillae, Hemiaster cotteaui, Fericosmus latus, Gregoiyaster lorioli, Schizaster eurynotus, Schizaster parkinsoni, Eupatagus dekonincki, Echinolampas lucae.