bluuebunny/crossref_metadata_2025_split huggingface dataset:
The structure of the Gulf of Suez (Clysmic) rift, with special reference to the eastern side
Authors: ROBSON DOUGLAS ARTHUR 
Published: December 2007

The stratigraphical sequence includes Palaeozoic (resting unconformably upon a Pre-Cambrian peneplane), Mesozoic and Tertiary rocks. These were deposited uniformly over the entire region although in Egypt the succession thins towards the south. Miocene rocks rest unconformably on earlier strata with which they contrast sharply in showing remarkable facies changes closely related to structural movements. Igneous activity was on a subdued scale and confined to Oligocene times. Dykes generally run parallel to the main Clysmic rift trend.
Rift faulting was initiated in Oligocene and continued into post-Miocene times. In addition to major marginal faults there are many tilted blocks which typify the pre-Miocene faulting. On the west some of these were eroded down to Basement before the deposition of Miocene sediments. In the east many such blocks exhibit only slight erosion and were probably not uplifted until late Oligocene times. The eastern boundary is marked by synthetic faults with downthrows of 1000 metres or more, but in one restricted area there is a downwarp broken by antithetic faults. The Miocene is characterized by anticlinal flexures generally associated with rejuvenation of Oligocene faults. There is no evidence of lateral movement but many of the faults follow ancient Pre-Cambrian trends. On the Sinai peninsula trend-lines show a twofold directional pattern, parallel to the Gulf of Akada and Gulf of Suez respectively. The angle between them suggests a series of conjugate pairs, originating as transcurrent faults in response to north-south compression. If this was the case, such strike-slip movements ceased before the deposition of the earliest Palaeozoic strata. These are at least as old as Carboniferous.
The area seems to have remained insulated from the great movements of lateral shiftwhich are claimed for the Akaba-Jordan rift and which are considered to be linked with the divergence of the Red Sea and the counter- clockwise rotation of Arabia. However, there is evidence to suggest that, since Eocene times, there has been a growing divergence of the margins of the Clysmic rift towards the south, producing a small counter-clockwise rotation of Sinai.
Thermal convection below the solidus in a mantled gneiss dome, Fungwi Reserve, Rhodesia
Authors: TALBOT CHRISTOPHER JOHN 
Published: December 2007

Previously unrecorded structures inside a mantled gneiss dome are described and interpreted as having important geological implications.
The gneisses which make up this basement structure were domed on at least three scales near the thermal acme of the post-Umkondo 500 m.y. orogeny in the Zambezi orogenic belt. Groups of domes on one scale occur inside those of successively larger scales, forming a hierarchy of structures which are interpreted as being due mainly to gravitational, rather than lateral forces.
The rocks involved have an essentially uniform density at the present and it is argued that a concentration of the regional orogenic thermal gradient would have induced unstable density gradients capable of driving thermal convection below the range of temperatures at which the rocks would have melted. For the domes (or convection cells) to have been preserved in the manner in which they are found the convection can only have been due to marginal mechanical instability and must have been stabilized after the first half-cycle of motion. Heat is conducted faster parallel to a gneissose foliation than normal to it and, in restricted ranges of thermal gradients, the mechanism of heat transfer, conduction or convection-with-conduction, may depend solely on the attitude of the foliation in relation to the thermal gradient. The hierarchy of structures is interpreted as a chain reaction of alternations of conduction and convection caused by the rotation of this thermal anisotropy as the structures formed.
The genetic model suggested is tested and found to be geologically acceptable in termsthe thicknesses of the convecting layers, their effective viscosities, and the time necessary for each structural pattern to develop.
It is argued that had the regional orogenic thermal gradient persisted or been exceeded the incipient convection preserved in Fungwi would have become cyclic. This would have resulted in the homogenization of the granite- syenitic gneiss to what would subsequently look like a normal magmatic rock in a very short time geologically. Other basement domes in the region are interpreted as recording a predictable sequence of normal gneiss domesto completely ‘igneous’ plutons.
The production of homogeneous rocks from a gneissose basement by convective overturn may be anticipated as a reasonably common orogenic phenomenon inside local thickenings of mechanically uniform rock sequences. It is suggested that this simple mechanism is a link often assumed or alluded to by earlier writers who have described migma and magma domes in close proximity.
Palaeontological prospects—the use of fossils in stratigraphy
Authors: McKERROW WILLIAM STUART 
Published: December 2007

T
he study
of fossils provides three main types of information:

1. the best method yet devised for recognising Phanerozoic time divisions over wide areas;
2. one of the best methods for distinguishing past sedimentary environments;
3. the only direct evidence of evolution through time, and thus a demonstration of the evolutionary relationships between those groups of animals and plants which have developed since the early Cambrian.
Palaeontology thus serves both Geology and Biology. This multiple service is even more evident today than in the past, especially in such fields as marine ecology. Not only are many modern ecological techniques being applied to fossil collecting, but the necessity to find out more about past environments has resulted in many palaeontologists wading and dredging to find out for themselves what is happening in modern seas.
This article is essentially a personal view of a palaeontologist who is attempting to use fossils to unravel past events and conditions in the light of present day processes. Of necessity, it cannot be a review of more than a small part of palaeontology. Most of the examples selected to illustrate this article are taken from fossil groups about which I have some experience; many of the points could equally well be made from other fossil groups. Drs. H. G. Reading and B. W. Sellwood have kindly made some comments on the typescript.
Fossils as time indicators
Some fossils can be used as a rough working basis for stratigraphy without considering them as much more than formed
Some points of interest concerning the Silurian inliers of southwest central Ireland in their geosynclinal context:
a statement
Authors: HARPER JOHN CHILDS , BRENCHLEY PATRICK JOHN 
Published: December 2007

In his discussion of geosynclinal development in the Silurian of the British Isles,
Ziegler (1970)
distinguishes land masses, shelf deposits, turbidite deposits and graptolitic shales. He further distinguishes between blocks such as the Midland Block and Eocaledonia (where passage from shelf to turbidite facies is sharp and associated with major fractures) and tectonic lands such as Cockburnland or the Irish Sea Land Mass (where the shelf record is only in the form of slumped shelly deposits).

Ziegler extrapolates his palaeogeographic maps across Ireland—a slimly documented area. He tentatively places the shelly succession of the Dingle Peninsula as part of the southern margin of Eocaledonia, and asserts that the turbidites and associated deposits of the Central Inliers seem to be related to the northern (Eocaledonian) margin of the trough. A contrary view has been suggested by Holland (1969 p. 208) who thinks that the Irish Sea Land Mass might have contributed sediments from the east.

Ziegler's palaeogeographic maps
(op. cir.
Figs. 3–6) show the trough as asymmetric, with turbidites mainly confined to the north-western side and graptolitic shales to the south-east. The evidence for this palaeogeographic interpretation in Ireland is slender and his conclusions are presumably based on his interpretation of the geology of the Central Inliers.

As will be seen in the following account there are some points concerning these inliers which are worthy of mention although their explanation is by no means clear.
The inliers are thought to fall into two groups and the argument for this is
Carbonatite-derived sediments in southeast Uganda
Authors: BLOOMFIELD KEITH 
Published: December 2007

F
ive carbonatite complexes
of probable Lower Miocene age occur along a
nne–ssw
line some 65 km in length in the southeast of Uganda, close to the Kenya border (
King & Sutherland 1966
). They are associated with the major central-type alkaline volcanoes of Mount Elgon and Kadam (Fig.
1
) which may also be assigned to the Lower Miocene on the basis of recent K-Ar age determinations (
Bishop, Miller & Fitch 1969
).

Sub-volcanic sediments, termed the Bugisu Series, crop out sporadically on the periphery of Mount Elgon and partly underlie Nkokonjeru, a neighbouring volcanic outlier. This Series was first described by Davies (1952 p. 7), who inferred four separate lacustrine basins of sedimentary deposition, three near the edges of the main Mount Elgon volcanic pile and the fourth underlying Nkokonjeru. Later, the Geological Survey of Uganda carried out a pitting and drilling programme on the northern slopes of Nkokonjeru and located various sub-horizontal sediments classified as ‘calcareous tuffs’, ‘ashy limestones’, and conglomerates in the lower part of the sequence.
The writer made a petrographic examination of available drill-core and found that most of the rocks were calcarenites and calcirudites containing abundant magnetite and apatite with small amounts of detrital pyrochlore––all apparently derived from carbonatites. Accordingly a detailed survey of the Nkokonjeru area was carried out, accompanied by intensive geochemical stream sediment sampling. This note summarizes the results.
Letter to the Editor
Authors: Powell Derek , Saxena Mahendra 
Published: December 2007

Sir,

The recent short communication concerning tillite horizons in the Chamba Himalayas of N. India (Powell and Saxena,
J. geol. Soc. Lond.
1971, p. 595) has prompted letters from Dr. J. B. Auden and Dr. V. J. Gupta. Dr. Auden has kindly pointed out our error in quoting Auden 1935 instead of Auden 1934 and 1955. He also draws attention to papers pertinent to the general discnssion of Himalayan Tillites, viz. Auden 1943, 1946, 1947, 1958 and Pilgrim and West 1928.

Dr. Gupta suggests an Upper Carboniferous to Permian age for tillltes in the Chamba area. The authors' tentative conclusion of a lower Carboniferous or older age for the Kalhel and Durgatti deposits was based on evidence presented by Gupta and Bedi (1970). Dr. Gupta now suggests the younger age for the tillites near Kalhel (Fuchs and Gupta 1971) on the basis of the presence of
Spirifer nagmargensis, S. nitrensis,
etc. in associated rocks. In support of this conclusion he cites Datta and Bhattacharya 1971 who report
Spiriferella rajah, Productus sp.
and
Modiola lidarensis
from the ‘Agglomeratic Slates’ in the north-eastern part of the Chamba area.

It is, however, not clear in Gupta (1970) or Fuchs and Gupta (1971) what is the detailed rock succession at Kalhel or how it can be correlated with the Agglomeratic Slates of Kashmir.
The new evidence from Dr. Gupta is welcome since only with more faunal evidence accurately located, will difficulties of correlation and dating be resolved.
Scourian-Laxfordian relationships in the Barra Isles
Authors: FRANCIS PETER W. 
Published: December 2007

The Lewisian rocks of Barra are a Laxfordian supra-structure of amphibolite facies gneisses and a Scourian infra-structure characterised by orthopyroxene bearing gneisses. Both units contain representatives of the Scourie Dyke suite; in the supra-structure they are highly deformed and folded; in the infra-structure they are relatively undeformed, unfolded, and retain original discordant relationships. The infra-structure also has several suites of intrusive igneous rocks earlier than the Scourie dyke suite, the most widespread being dykes of dioritic composition.
The same sequence of Laxfordian deformation may be recognised in both units. Folding occurred in the supra-structure under amphibolite facies conditions, which continued after deformation ceased. In the infra-structure, evidence for a pre-Scourie dyke pyroxene granulite facies metamorphism is preserved. The Scourie dykes of the infra-structure have pyroxene granulite facies mineral assemblages resulting from intrusion into hot or dry country rock gneisses.
Probably a very old cover to basement relationship is preserved in the area, which was first deformed in the Scourian orogeny, and then subsequent Laxfordian deformation of the interface between the two major units produced overall structure of the area.
The geology of the continental shelf between Luderitz and Cape Town (Southwest Africa), with special reference to Tertiary strata
Authors: DINGLE RICHARD V. 
Published: December 2007

The geology and morphology of the continental shelf between Luderitz and Cape Town are described. The shelf is shown to be a thick sediment wedge constructed mainly during Cretaceous times, with a thin capping of Lower Tertiary, Upper Tertiary and Holocene sediments. Shallow-water sediments dominate the Upper Tertiary succession, and four main facies are identified which are controlled to a great extent by the Lower Tertiary ridge; a topographical high possibly representing secondary features related to basement structures at depth. ?Coniacian, ?Eocene, ?Miocene and ?Pliocene transgressions are recognized.
Earliest Cretaceous sediments are probably Aptian or earlier. A progressive decrease in the sedimentation rate since Cretaceous times is postulated and present-day regional disparities in shelf depth are explained in the light of subsidence and sedimentation rates. The double shelf break has been in existence since at least Lower Tertiary times and has been periodically modified by erosion and sedimentation. Bottom currents have kept the outer shelf area sediment-free since ?Pliocene times. The distribution of organic-rich and authigenic mineral-rich sediments is mentioned.
The Cenozoic history of the southern Atacama Desert, Chile
Authors: MORTIMER CEDRIG 
Published: December 2007

Four episodes of landscape evolution are recognized, each of which has led to the development of a regional erosion surface. The first phase began upon elevation of northern Chile above sea level in the late Mesozoic, and each subsequent phase commenced with a major incision of drainage into the preceding landscape. Radiometric dating of pyroclastic flows shows that the earliest elements of the present topography already existed in the Lower Eocene, and that most landforms had developed by the Middle-Upper Miocene. Deep canyon formation characterized the latest erosional phase which commenced in the Upper Miocene and is still continuing.
Tectonic elevation of the Cordillera de la Costa in relation to the longitudinal depressions seems to have occurred early in the landscape history, though later remobilization along major structures has since taken place.
Erosional landforms in the high Andes are often blanketed by constructional volcanic features and the migration of eruptive centres since Miocene times has displaced the continental watershed to the east.
Tectonically induced relative sea level changes have caused late Tertiary transgressive deposits in the littoral region to have been terraced during an irregular marine regression. The landscape history which spans the whole of the Tertiary indicates that Andean relief generation has been a prolonged pulsative process.
Supergene enrichment of the copper deposits took place under the older erosion surfaces between the Lower Eocene and the Upper Miocene, and the economic viability of a prospective mine can be largely predicted from the overlying topography.
Seismic reflection profiles of the continental margin bordering the Rockall Trough
Authors: BAILEY ROBIN J. , GRZYWACZ JAN M. , BUCKLEY JOHN S. 
Published: December 2007

From 25 seismic reflection profiles of the continental margin of the British Isles bordering the Rockall Trough (54° to 57°n Lat.), 15 are selected for description. They reveal a marginal sedimentary succession recording two major phases of subsidence and sedimentation, with an intervening phase of uplift and erosion. Although the Rockall Trough may well date from late Jurassic or early Cretaceous times, a late Cretaceous age of the first phase of subsidence and sedimentation is likely during which a marginal prograding sedimentary series was deposited. The ensuing phase of uplift and erosion is equally tentatively referred to the Palaeocene Epoch. The subsequent transgression and deposition of the overstepping upper sedimentary series is of possible Eocene to Recent date.
There is evidence to suggest that, in addition to these regional phases of subsidence and uplift, the continental margin at 55°20'n Lat. suffered faulting involving major east-west dextral displacement. This occurred prior to the deposition of the older prograding sedimentary series. The sense of movement within the fault zone, and the location and general trend of this zone, are appropriate for correlation with a prolongation or splay of the Great Glen Fault System.
The structure and emplacement of the Rio Fortaleza Centred acid complex, Ancash, Peru
Authors: KNOX GORDON J. 
Published: December 2007

The Rio Fortaleza centre is one of four known centred complexes of the Coastal Batholith and is a hypabyssal ring-dyke complex. Subterranean cauldron subsidence is represented by a bell-jar pluton, while a later ring-dyke may have produced subaerial pyroclastics associated with a caldera.
Inclusion screens represent the remnants of spalled-off country rock and ring-fault mylo-nites, tuffisites and gas breccias with limited hydrothermal mineralizations are indications of its high-level nature.
The two ring-dykes, some 22 km in diameter, are structurally controlled with polygonal outcrop patterns related to the regional joint pattern. At depth, the intersections of major wrench fractures may have focussed the magmas and delimited the symmetrical disposition of the four centres.
The centred complexes show a close relation between plutonism and vulcanism and prob­ably represent the basal remnants of caldera volcanoes that supplied some of the extrusive envelope of the batholith.
Apollo and the geology of the Moon
Authors: SCHMITT HARRISON H. 
Published: December 2007

The probability is very great that the geology of the decade of Apollo will become one of the fundamental turning points in the history of all science. For the first time the scientists of the Earth have been presented with the opportunity to interpret their home planet through the direct investigations of another. Mankind can be proud and take heart in this fact.
The interpretive evolution of the Moon can be divided now into seven major stages beginning sometime near the end of the formation of the solar system. These stages and their approximate durations in time are as follows:
1. The Beginning—4.6 billion years ago
2. The Melted She11—4.6–4.4 billion years ago
3. The Cratered Highlands—4.4–4.1 billion years ago
4. The Large Basins—4.1–3 9 billion years ago
5. The Light-colored Plains—3.9–3.8 billion years ago
6. The Basaltic Maria—3.8–3.0 (?) billion years ago
7. The Quiet Crust—3.0 (?) billion years ago to the present
The Apollo explorations that permit us to study these stages of evolution each have contributed in progressive and significant ways. Through them we now can look with new insight into the early differentiation of the Earth, the nature of the Earth’s protocrust, the influence of the formation of large impact basins in that crust, the effects of early partial melting of the protomantle and possibly the earliest stages of the breakup of the protocrust into continents and ocean basins.
Sedimentation and tectonism (?Permo-Triassic) on the margin of the North Minch Basin, Lewis
Authors: STEEL RONALD J. , WILSON ALAN C. 
Published: December 2007

The (?) Permo-Triassic Stornoway Formation is
c
. 4000 m thick and consists mainly of conglomerates.

The sediments were deposited on alluvial fans as mudflow, streamflood and braided stream deposits, and on floodplains as channel and overbank sediments. In each of the lower, middle and upper units of the Formation there is evidence of two major phases of alluvial fan-building. It is suggested that these phases were tectonically controlled and that within each alluvial fan sequence the time-trend of sedimentation reflects the rate of basin subsidence. Fining-upwards fan sequences suggest basin-margin faulting of gradually decreasing intensity; coarsening-upwards sequences suggest a history of increasing fault intensity. Floodplain deposits, overlying either type of sequence, indicate a cessation of tectonism and a gradual overlap of the old fault lines by fine-grained sediment.
The Stornoway Formation is seen as the sedimentary fill within the deep, western margin of an asymmetrical North Minch (Permo-Triassic) Basin. Palaeogeographic reconstructions through time suggest that this western margin shifted westwards as the locus of faulting and fault-generated sedimentation migrated by 15 km from the Minch Fault.
Geochronology of the Channel Islands and adjacent French mainland
Authors: ADAMS C. J. D. 
Published: December 2007

Rb-Sr whole-rock dating of igneous and metamorphic rocks of the Channel Islands region has delineated the following major events: 1) Formation of the Pentevrian basement gneisses
c.
2600 Ma ago in the northern Guernsey, Alderney and Cap de la Hague region. 2) Possible isotopic rejuvenation of these gneisses during a second metamorphic episode
c.
1950 Ma ago. 3) Formation of Pentevrian gneisses in the southern, St Malo-St Brieuc region, 1000–1100 Ma ago. 4) Deposition of the Brioverian sedimentary series in the interval 650–1000 Ma. 5) Emplacement of igneous rocks 650–690 Ma ago during initial phases of the Cadomian Orogeny (late Precambrian) followed by 6) a main regional metamorphic event 620–650 Ma ago, and 7) a post-metamorphic igneous phase 560–610 Ma ago. 8) On Jersey a further post-tectonic granite phase, 480–520 Ma, can be recognized

Within this framework, nearly 130 K–Ar and Rb–Sr mineral ages from the area are interpreted as reflecting initiation of cooling and uplift of the Cadomian orogen as a whole in late Precambrian or Cambrian times.
Only a very few, young minor intrusions are connected with Variscan orogenic events.
Some preliminary comparisons can be made with late Precambrian igneous and metamorphic rocks elsewhere in the Massif Armoricain, southern Britain, eastern Canada and U.S.A.
Structural style in slump sheets: Ludlow Series, Powys, Wales
Authors: WOODCOCK NIGEL H. 
Published: December 2007

The slump deformation in sediments of the Montgomery Trough is described and compared with tectonic deformation. The structures within each slump sheet are systematically oriented with respect to the inferred palaeoslope. The slump folds have lognormal size distributions and their range of styles closely matches that of tectonic folds. Similar folds are rare, and deformed lineations show that buckling was important during slump fold formation. Axial microfold lineations and axial plane cleavages are associated with the slump folds. Also present is a spaced cleavage, thought to have formed in soft sediment.
Structural style cannot discriminate between slump and tectonic structures. The distinction may in many cases rely on subjective and uncommon features of soft-sediment deformation, such as the absence from folds of tension cracks and veins.