Diagenesis is the sum of those processes whereby an originally sedimentary assemblage attempts to reach and maintain an equilibrium with its environment. Numerous factors influence and affect the diagenesis of sedimentary elastic assemblages - fundamentally unstable when deposited but never reaching equilibrium ith their environment. The interrelationship of these factors, however, precludes the identification of any single factor as wholly controlling the diagenesis of elastic sediments. The multifactorial nature of diagenesis is illustrated here by reference to the Middle Jurassic Dogger Formation and Ravenscar Group which outcrop on the North Yorkshire Moors and the Brent Group from Wells 3/3-1, -2, and -3 in the Ninian Field, and 210/15-2, also in the Northern North Sea.The Ravenscar Group is interpreted as being deposited in a fluvio-deltaic complex. Here, attempted equilibration of non-marine sediments with their pore waters resulted in a variety of diagenetic modifications. These are interpreted as being influenced strongly by bacterial degradation of organic matter, which lowered pH and then reduced Eh. This reduction of pH caused feldspar dissolution and muscovite neomorphosis to kandites throughout. Similarly, in the texturally and inineralogically mature sandbodies, quartz overgrowths and veriniform kandites precipitated from oxygenated pore waters, whilst chlorite and overgrowths formed in anoxic pore waters. This resulted in complete reduction of porosity in, and cementation of, finer and texturally less mature overbank sands. Conversely, channel sands were cemented into rigid but porous quartzose frameworks. In addition, soil horizons of sphaerosiderite developed as standing water on the floodplains stagnated. Bacterial ferric iron reduction throughout the water table then raised the pH and extensive siderite cements were precipitated. During burial, calcium carbonate saturated formation waters migrated into the remaining porous sandbodies and precipitated replacive ferroan calcite. In marine elastics, meanwhile, illite and potassium-feldspar overgrowths precipitated before in situ bacterial processes lowered pH here also. This resulted in dissolution of feldspars, muscovite neomorphism and precipitation of vermiform kandites. Subsequently, pH rose and ferroan calcite cementation occurred.It is suggested that "aggressive fluids" migrated into the larger connected sandbodies during burial. They dissolved the carbonate cements and precipitated dense pockets of blocky kandites. These sediments were little affected during continued burial. However, their Recent weathering may have dissolved carbonates and feldspars as well as neomorphosing chlorite to vermiculite.The reservoir rocks of the Ninian Field have formed from mature quartz-rich elastic sediments which accumulated in a transgressive sequence above Liassic mudrocks which was subsequently incised into by a fluvial system. Diagenetic modifications of the original sediments are similar to those of the Ravenscar Group, although neither chlorite nor soil horizons were observed in the wholly non-marine sediments. Porosity in marine sediments is occluded by extensive authigenic illite within a generally quartz framework. The effects of the fresh water table are also seen in the marine sediments over which the delta prograded. Then, during burial, ferroan calcite cementation and subsequent leaching and blocky kandite precipitation occurred here also. Hydrocarbon maturation and migration into the reservoir was preceded by alteration of pre-existing carbonates to ankerite, and. minor illitisation of blocky kandites. However, the only effort which can be related to oil emplacement is the widespread pyritisation around the oil-water contact.The sandstones from 210/15-2 are interpreted as formed from coarse elastic sediments which accumulated in a shallow-marine nearshore environment, possibly incised into by distributary channels. Initial marine connate water precipitated potassium-feldspar overgrowths before bacterial processes lowered pH and caused widespread kandite formation. Subsequently, these sediments were affected by ferroan calcite cementation, then leaching and blocky kandite precipitation. Although oil has migrated into these sediments, no other effects were observed.In addition to the factors which have been proposed previously as influencing diagenesis, I should like to propose that the climate of both the source area and of the depositional basin was of fundamental importance to diagenesis and many of the features observed in these rocks may be related to the original tropical climate. Moreover, as a result of the fundamental stability of the quartzose frameworks established during eogenesis, this climatic "finger print" may be recognised in all these sediments despite their subsequent diverse history.

The Scarborough Formation is the youngest marine horizon of formation status within the dominantly deltaic Aalenian - Bajocian Ravenscar Group, Cleveland Basin, northeast England. Sedimentary facies analysis has been performed on the three conformable lithostratigraphic units which make up the bulk of the Scarborough Formation outcrop: Blea Wyke, Byland Limestone and Crinoid Grit Members. This form of analysis was performed in an effort to determine the depositional environments of the members. The information derived from the study enables one to trace the palaeogeographic evolution of the Cleveland Basin throughout much of Scarborough Formation times.The clastic Blea Wyke Member [6 facies] is attributed to deposition in a shallow [<4m], essentially microtidal,delta-destructive marine embayment. This embayment formed through non-eustatic marine transgression initiated by the compactional subsidence of an abandoned [Gristhorpe Member] delta lobe. Open to the east, the embayment covered some 2000km2 of the Cleveland Basin when fully established. A range of sand bodies evolved on the silty embayment floor in response to spatial and temporal changes in the wind-forced wave and current regime. These sand bodies included subtidal shoals, laterally extensive storm-emplaced sand blankets, and a classic delta-destructive sheet sand formed through the landward translation of a low-profile barrier bar.Under sustained rate-of-subsidence controlled marine transgression, clastic input to the Blea Wyke Member embayment eventually waned. In response, the overlying Byland Limestone Member [6 facies] was deposited in the western part of the Cleveland Basin in the form of a carbonate-dominated lagoon-barrier-inner shelf complex. The barrier component of the complex evolved through transgressive upward-shoaling under the influence of wind-forced wave and current activity. Composed of pellet lime grainstones, it protected a lagoon within which the dominant deposits were pellet lime mudstones, wackestones and packstones. Lithological and faunal similarities between the lagoon and inner shelf suggest that much of the shelf region may have comprised former back-barrier lagoon-fills exhumed during transgression.Byland Limestone Member times were terminated by an acceleration in the rate of marine transgression followed by tectonic uplift and subsequent geomorphic decay of the major landmass to the north [Mid North Sea High]. Transgression generated an east-west orientated epeiric seaway connecting the Sole Pit Trough with an areally restricted Pennine Massif. Within this seaway, clastic sediment derived chiefly from the Mid North Sea High was deposited in the form of a progradational, regional-scale composite sheet sand body: the Crinoid Grit Member [8 facies]. Deposition occurred under the combined influence of tidal currents, wind-forced currents and wave activity. Three main facies belts are recognised: paralic tidal sandwave complex, storm-dominated inner shelf and sandy middle shelf. The presence of a tidal sandwave complex is particularly interesting; it indicates that the forging of a marine connection to the west of the Cleveland Basin was necessary before tidal cyclicity could become prominent within the basin.

This thesis is an attempt to combine a number of different approaches as part of a wider attempt to re-interpret the late Quaternary history of the Vale of Pickering and Northern Wolds in Yorkshire. This involved the critical analysis of part evidence together with the collation and interpretation of data from a variety of sources, some published, some unpublished but mostly from field work.The course of the research followed a number of different lines. The first of these was to study the sedimentary data from glacial and pro-glacial deposits in the Vale of Pickering to assess their age and environment of deposition. The sediments were mapped in the field and analysed in the laboratory. A glacial outwash rather than lake-beach origin was proved for an important group of these sediments. The sedimentary data from the Vale of Pickering showed that ice had undoubtedly advanced further into the area than had been envisaged by Kendall at the turn of the century. - this was supported independently by geomorphological evidence and more sedimentary data from the northern Yorkshire Wolds escarpment. In the western end of the Vale, a thicker lobe of ice than that supposed by Kendall seems to have advanced into the area from the Vale of York, but its furthest limits cannot be shown from data available at the moment.On the Yorkshire Wolds an attempt was made to delineate the advance of the Late Quaternary ice, but unfortunately the data was so poor that no firm limits could be drawn. Glacial outwash sediments were found at several scattered sites and compared with those found in the Vale, some similarity was proved, suggesting that meltwater from late Quaternary glaciers had flowed across the Wolds and that ice from the Vale had overtopped the Wolds scarp along much of its length. The soils were analysed and found to have a higher blown sand content than suspected previously. The blown sand content increased towards the northwest, suggesting a probable glacial outwash source.The dry valleys were studied and new light shed on the processes which may have contributed to their formation. In addition evidence of periglacial evidence from the whole region was collected, described and assessed. Finally it was found that the structural lines of disturbance which traverse the chalk of the northern Wolds could easily be mapped from aerial photographs. These were mapped and included in the thesis as a small contribution to the solid geology of the area, even though they only impinge indirectly upon the main scope of this study.

The Penrith Sandstone and brockrams (breccio-conglomerates) are continental red-beds of Lower Permian and Permo-Triassic ages respectively. The brockrams are predominantly the deposits of coalescing alluvial fans which accumulated as the products of subaerial sheetflood, transitional debris flow and braided river processes at the margins of desert basins bordering the upstanding Lake District. The fans were deposited on an irregular topography which is demonstrated to have a probable minimum preburial relief of 250 to 300 metres in west Cumbria. The cross-stratified Penrith Sandstone of the Eden Valley accumulated as the foresets of large scale (up to 100 metres width) aeolian dunes orientated in response to a uniform east-south-easterly palaeowind. Dune-bedding within these deposits indicates a crescentic-downwind (barchanoid) configuration for the dune slipfaces. The stratigraphic unit termed the 'Upper Brockram' is believed to represent the deposits of ephemeral streams (arroyos) which flowed through and reworked part of the aeolian sand sea of the Penrith Sandstone. Nodular carbonate profiles occurring within sandstone/siltstone horizons intercalated with distal alluvial fan deposits in west Cumbria are interpreted as immature caliche soil horizons and represent periods of surface stability (non-deposition) of indeterminate length. Petrographic evidence indicates the most important process of formation to have been that of replacement of the detrital quartz component by microcrystalline non-ferroan calcite. Extensive post-depositional (diagenetic) modification to the mineralogy and texture of the brockrams of west Cumbria has resulted from the mechanical infiltration of clay, the dissolution of the less stable detrital components (primarily volcanic clasts), replacement by secondary clay and the precipitation of interstitial and void-filling authigenic clay, a hydrated haematite precursor mineral, ferroan and non-ferroan calcite and gypsum. Most reactions are considered to have occurred as stages within an evolving diagenetic sequence.

This study is based on palynological investigations at three sites in Java: Bandung Lake, Trinil and Bumiayu. At Bandung Lake (Holocene) three cores were studied, while surface section samples were studied from Trinil in East Java (Middle Pleistocene) and Bumiayu in Central Java (Upper Pliocene). The Trinil site is well known for its hominid fossils.The pollen flora at each site is fully described and illustrated while the pollen record at each location is used to reconstruct their vegetational, environmental and climatic histories. An attempt has also been made to determine whether palynology can be used to assist in dating these deposits. At all three sites, the character of the local vegetation is better reflected than that of the regional vegetation.One of the Bandung sites (Rancaekek) was radiocarbon dated, suggesting deposition between 11,000 and 7,000 yr BP and represents a freshwater lake deposits. The lake gradually shallowed toward 7,000 yr BP, at which time it was drained. The regional pollen component suggests climatic amelioration at about 8,000 yr BP, possibly reflecting the maximum incoming of solar radiation experienced in the Northern Hemisphere about 9,000 yr BP.Studies at Trinil revealed a mosaic of forest and open vegetation growing on a lahar. The former climate at this locality was probably markedly seasonal, not unlike that of the present day. Palynology conclusively demonstrates that this sequence is Pleistocene rather than Pliocene in age. The palynological record at Bumiayu reflects a regressive sequence with lagoonal and freshwater lacustrine environments (Kalibiuk Formation) followed by freshwater fluvial deposition (Kaliglagah Formation). The climate during the deposition of this sequence was markedly seasonal. The data support an Upper Pliocene age for the Bumiayu sequence.Three taxa are shown to have become extinct in Java during the Plio-Pleistocene. These are Stenochlaena lamrifolia and S. areolaris, which become extinct at the end of the Pliocene, and Daczydium, which is thought to have become extinct during the Holocene.

No description available.

No description available.

No description available.

A minor eruption of Mount Saint Helens in Washington State U. S. A. in 1984, triggered the formation of a debris flow in the headwaters of the North Fork Toutle River. As the debris flow progressed downstream it transformed through the incorporation of water and the loss of sediment and within 34 kilometres became a muddy flood. The deposits produced by the transforming flow and associated recessional flows that followed in its wake, exhibited a coarse grained depositional continuum from debris flow to stream flow, including deposits with intermediate sedimentological characteristics termed "hyperconcentrated flow deposits".The systematic and detailed sedimentological analysis of these deposits, combined with information concerning the characteristics of the flow, has allowed the delineation of hyperconcentrated flow deposits within the debris flow/stream flow depositional continuum and hence the establishment of criteria for the recognition of coarse grained hyperconcentrated flow deposits in the volcaniclastic environment of Mount Saint Helens. Hyperconcentrated flow deposits are generally homogeneous, matrix-supported, unstratified (except where defined by sub units), have sorting characteristics intermediate between debris flow and stream flow and can exhibit a bimodal, generally non imbricate, clast fabric as a function of clast size. Coarse-tail inverse grading may occur but it is weak, or restricted to sub units. Use of these criteria enabled the recognition of hyperconcentrated flow deposits within depositional sequences produced earlier in the eruptive history of Mount Saint Helens.The analysis of Permo-Triassic alluvial fan deposits on the Isle of Lewis Scotland, revealed that elements of the debris flow/stream flow depositional continuum could be recognised by the application of the criteria established in the volcaniclastic environment of Mount Saint Helens.

The Ostracoda from nine sections of the Lower Fars Formation, Northern Iraq, Tel-Hajer well-1, Sheikh Ibrahim locality, Dohuk locality, Sheikhan locality, Bashiqa locality, Kirkuk well-208, Bai-Hassan well-33, Hamrin well-2 and the Naft Khana well-34, have been studied in detail.One hundred and nine Ostracod species/subspecies belonging to 50 genera/subgenera are described, of which one genus, one subgenus and 70 species are new. Five species are assigned to species previously described from western India. Five species are compared with other species from W. India, Iran, Turkey and France. Three species are regarded as having affinities with new species described in this thesis and 26 species are left under open nomenclature mainly because of lack of material or the impossibility of observing the internal details.Biostratigraphically, the Lower Fars Formation in the Sinjar area is divided into three Assemblage Zones, these zones are applicable only to N. Iraq, but make a starting point for future work in the area. In the Kirkuk area, the saliferous beds proved completely barren, but the upper Red, Seepage and Transition beds yield Ostracods although the assemblages recognised are at present only regarded as tentative, because the samples are ditch cuttings.Palaeoecology is discussed in terms of oxygenation, alaeoclimate, salinity and the trends in the depositional environment of the Lower Fars Formation.The affinities of the present genera and species are discussed from a palaeogeographical view point in relation to the adjacent and related regions. Three Miocene Ostracod provinces are proposed, namely a western India province, a Zagros shelf province and a southeast Turkey province.