A B S T R A C TVertical sequence analysis within 1500-2500 m thick coarse-grained coalfield successions allows six sedimentary associations to be distinguished. These are interpreted in terms of depositional environments on, or related to alluvial fans which fringed a fault bounded source region. (i) Topographic valley and fanhead canyon fills: occurring at the bases of the coalfield successions and comprising sporadically reddened, scree, conglomeratic thinning and fining upward sequences, and fine-grained coal-bearing sediments. (ii) Alluvial fan channels: conglomerate and sandstone filled. (iii) Mid-fan conglomeratic and sandstone lobes: laterally extensive, thickly bedded ( 1-25 m) and varying from structureless coarse conglomerates and pebbly sandstones, to stratified fine conglomerates and cross-bedded sandstones. (iv) lnterlobe and interchannel : siltstones, fine-grained sheet sandstones, abundant floras, thin coals and upright trees. (v) Distal fan: 10 cm-1.5 m thick sheet sandstones which preserve numerous upright trees, separated by siltstones and mudstones with abundant floras. and coal seams. The sheet sandstones and normally arranged in sequences of beds which become thicker and coarser or thinner and finer upwards. These trends also occur in combination. (vi) Lacustrine: coals, limestones, and fine-grained, low-energy, regressive, coarsening upward sequences.Proximal fan sediments are only preserved in certain basal deposits of these coalfields. The majority of the successions comprise mid and distal alluvial fan and lacustrine sediments. Mid-fan depositional processes consisted of debris flows and turbulent streamflows, whilst sheetfloods dominated active distal areas. A tropical and seasonal climate allowed vegetation to colonize abandoned fan surfaces and perhaps resulted in localized diagenetic reddening. Worked coals, from 10s cm-20 m thick, occur in the distal fan and lacustrine environments.These alluvial fan deposits infill 'California-like' basins developed and preserved along major structural zones. In many of their characteristics, in particular the occurrence of thinning and fining, and thickening and coarsening upward sequences and niegasequences. these sediments have similarities to documented ancient submarine fan deposits.
On the Eastern Flank of the South Oman Salt Basin lies a Cambrian to Recent sequence much affected by the withdrawal and dissolution of underlying Infracambrian salt. Salt withdrawal began after burial by only a few hundreds of metres of Cambrian continental sands, and salt dissolution has taken place periodically up to the present, initially near-surface and later in the subsurface. Salt removal has (1) resulted in the collapse of masses of dolomite and shale formerly interbedded with the salt, (2) influenced the large-scale geometries of sedimentary bodies within the overlying succession, (3) affected the distribution of sedimentary facies when rates of salt removal balanced or exceeded sedimentation, (4) allowed the preservation of parts of the succession otherwise eroded at this basin margin, and (5) caused folding and fracturing of Cambrian to Recent sediments.More than 2 • 109 m 3 of oil (12 • 109 bbls) is estimated to be present in four types of hydrocarbon trap related to salt removal. In terms of importance these are: large turtleback anticlines resulting from the inversion of former peripheral synclines, truncation traps rimming eroded turtle-back anticlines, small anticlines draped over residual masses of dolomite and shale, and porous and fractured dolomites within such residual masses.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.