Showing papers on "Permian published in 1969"

Lissamphibian origins: possible protolissamphibian from the lower permian of oklahoma.

Abstract: A new genus and family of rhachitomous labyrinthodont amphibian, related to the Upper Paleozoic Dissorophidae and Trematopsidae, may be ancestral to some or all of the modern Amphibia. Doleserpeton occurs in Lower Permian fissure fill deposits in southwestern Oklahoma. It is unique among nonlissamphibian tetrapods in that it possesses pedicellate, bicuspid teeth together with nearly monospondylous vertebrae in which the main central element is a pleurocentrum. Doleserpeton may have been utilizing the food resources of the upland, terrestrial environment in a novel fashion for rhachitomes.

The Mesozoic of New Zealand: Chapters in the history of the Circum-Pacific Mobile Belt: 22ND WILLIAM SMITH LECTURE

Abstract: The Mesozoic includes the later history of the New Zealand Geosyncline, the Rangitata Orogeny that ended the geosynclinal phase, superposing a new structural system, and the beginning of the transgression that followed. The main elements of the geosyncline, from west to east, are: (1) a foreland, metamorphosed and intruded by granite in a relatively high temperature/low pressure environment; (2) a geosynclinal margin or hinge-line, the median tectonic line of Landis and Coombs; (3) a western or marginal belt of geosynclinal sediments (Hokonui Facies) relatively fossiliferous, apparently deposited over the Pacific edge of the sial and now forming a western marginal syncline; (4) an abrupt facies junction marked by ultramafic intrusions and Permian volcanics, perhaps the early Mesozoic oceanic boundary of sialic crust; and (5) an eastern belt of relatively unfossiliferous deformed sediments of the greywacke suite (Torlesse Facies), metamorphosed in a high pressure environment, their lower parts to schist. The western or Hokonui zone records rapid and almost continuous marine sedimentation during the Triassic and Jurassic, with some brief local interruption during the Middle Jurassic. The eastern or Torlesse zone of thick quartzo–feldspathic greywackes and argillites, with some spilitic lavas, occupying a Pacificmargin trench, has proved difficult to interpret owing to structural complexity, lithological monotony and scarcity of fossils. The metamorphic boundaries vary in age in different places, and the known fossils show a nonrandom distribution in age and space, as if basins of rapid sedimentation migrated up and down its axis throughout Permian to Tithonian time, reacting to variable thermal gradients. The Rangitata Orogeny began with precursor movements in the Middle Jurassic but climaxed in the Lower Cretaceous. The orogeny led to the main metamorphism and folding of the geosyncline, long the East phases of granite intrusion in the foreland, and the torsion and rupture of the geosyncline along the transcurrent Alpine Fault. In the Aptian, basins within the New Zealand geosyncline received sediment still of geosynclinal facies, so that it remains uncertain whether deposition was locally continuous or whether the Cretaceous is everywhere unconformable on underlying rocks. Synorogenic breccias (pre-Campanian) locally overlie schist and foreland granites that have been dated isotopically as mid-Cretaceous, and thus point to rapid uplift and erosion. By the Macstrichtian, freshwater and marine sediments indicate peneplanation and dominantly chemical weathering. The Tasman Sea is first evident in the Cretaceous, and the Cretaceous transgression, continuing in the Tertiary, reduced the land to a changing archipelago. Early Mesozoic structures are consistent with a simple continent–ocean boundary and trench trending north-west, parallel to the Mesozoic Darwin Rise. The Cretaceous orogeny superposed north-east trending structures that have dominated later history; their northern parts face the Pacific and parallel a section of the East Pacific Rise, but their southern parts face the Tasman Sea in a kind of scissors or ‘anceps’ structure. The change from a single Pacific margin to the present anceps structure facing both the Pacific and Tasman is consistent with post-Jurassic development of the Tasman and other marginal ocean basins during the Cretaceous orogeny, which entailed considerable horizontal movements of the crust. New Zealand geology can be extrapolated onto the surrounding shallow sea-floors, underlain by subcontinental crust, using evidence from outlying islands, submarine geology, and geophysics. The speculative process of rationalizing Lower Mesozoic palaeogeography is made easier if it is assumed that the early Mesozoic arc, now sinuous, was originally straighter, and that the marginal ocean basins now interrupting its course developed during the Cretaceous deformation that led to its curvature.

Late Paleozoic Glaciation: I, South America

Abstract: Glacial activity is recorded in rocks of Early, Middle and Late Carboniferous and Early Permian(?) age in Argentina and Bolivia, and in Carboniferous and Permian(?) strata of the cratonic Parana basin in Brazil, Uruguay and Paraguay. Direct evidence for glaciation in the four Andean basins consists of a single striated floor and common striated clasts in diamictites and associated strata. Many Andean diamictites are intercalated in sequences which contain marine invertebrate fossils and turbidites. There is abundant evidence in the form of sandstone inclusions showing soft sediment deformation that subaqueous mass movement took place during deposition. These rocks are therefore interpreted as resedimented till. Pebbly shale and varvelike rocks formed from ice rafting in marine and lacustrine environments. The glacial impress is slight in the continental facies as developed in fluvial strata of the Rio Blanco basin. The dominant feature of the glacial Itarare Subgroup of the eastern border and of the Aqui-dauana Group of the western border of the Parana basin is fluvial reworking of diamictite during intervals between glacial advances. This extensive reworking has removed much primary evidence of glaciation but the presence of about 30 striated floors and surfaces within the sequence is unequivocal. Subaqueous mass movement and ice rafting also took place. Ice centers apparently developed in rugged highlands within the Andean orogenic belt. Alpine or piedmont glaciers, or both, flowed downward onto narrow shelves, and till then moved into the marine portions of the basins by mudflow and sliding. The continental portions of the basins lay generally eastward of the marine areas and a topographically mature terrane still farther east was affected only slightly by glaciation, presumably because it was distant from glacial centers and lay at a relatively low elevation. Continental glaciers of eastern South America probably radiated from centers located in South West Africa before separation of the continents, flowing northwestwardly onto the Brazilian shield and thence into the Parana basin. Three separate lobes of ice occupied the Uruguayan shield, parts of Parana and Santa Catarina states, and the state of Sao Paulo. A marine seaway occupied the basin center at times and was succeeded by a large body of fresh water at the time of glaciation of the western border of the basin. The southern portion of the Asuncion arch was a glacial source which yielded debris northeastwardly from the western border after glaciation ceased in the east. The Parana sequences suggest 10 distinct ice advances separated by fluvial activity that may represent interglacial periods. This extensive glaciation resulted because the region was in high latitudes (as indicated by paleomagnetic data) through much of the Carboniferous and the Early Permian. The restricted glaciation of the Andean region was more closely controlled by elevation, possibly because of its position in somewhat lower latitudes.

New Permian Brachiopods from West Texas

Abstract: Thirty-five new genera are described, 27 of them based on new species. They are classified by superfamily as follows: Enteletacea: Acosarina (A. dorsisulcata, new species). Davidsoniacea: Goniarina (G. pyelodes, new species), Tropidelasma (T. culmenatum, new species). Chonetacea: Chonetinetes (C. reversus, new species), Micraphelia (M. scitula, new species), Rugaria (Chonetes hessensis R. E. King), Sulcataria (Chonetina? rostrata Dunbar and Condra), Undulella (U. undulata, new species). Strophalosiacea: Acritosia (A. magna, new speccies), Agelesia (Aulosteges triagonalis R. E. King). Richthofeniacea: Collumatus (C. solitarius, new species), Cyclacantharia (C. kingorum, new species), Hercosestria (H. cribrosa, new species), Hercosia (Richthofenia uddeni Bose), Sestropoma (S. cribriferum, new species). Productacea: Anemonaria (A. inflata, new species), Dasysaria (D. undulata, new species), Oncosarina (O. spinicostata, new species), Thamnosia (T. anterospinosa, new species). Lyttoniacea: Petasmaia (P. expansa, new species) . Rhyncfionellacea: Amphipella (A. arcaria, new species), Bryorhynchus (Camarophoria? bisulcata Shumard), Divaricosta (D. squarrosa, new species), Petasmatherus (P. opulus, new species), Phrenophoria (P. subcarinata, new species), Pontisia (P. stehlii, new species), Strigirhynchus (Rhynchonella? indentata Shumard), Tautosia (T. fastigiata, new species). Spiriferacea: Lepidospirifer (L. angulatus, new species). Spiriferinacea: Sarganostega (S. transversalis, new species), Xestotrema (Spirifera pulchra Meek) . Reticulariacea: Anomaloria (A. anomala, new species), Astegosia (Squamularia guadalupensis subquadrata Girty). Dielasmatacea: Plectelasma (P. kingi, new species) . Cryptonellacea: Texasia (T. elongata, new species). The genus Cooperina Termier, Termier and Pajaud, based on material from the Glass Mountains, Texas, was assigned by its authors to the Thecideidina. Evidence is adduced here to show that it is classified more properly among the Strophalosiacea of the Productidina and that it is unrelated to the thecideids.

Cycads: Fossil Evidence of Late Paleozoic Origin

Abstract: Plant fossils from Lower Permian strata of the southwestern United States have been interpreted as cycadalean megasporophylls. They are evidently descended from spermopterid elements of the Pennsylvanian Taeniopteris complex; thus the known fossil history of the cycads is extended from the Late Triassic into the late Paleozoic. Possible implications of the Permian fossils toward evolution of the angiosperm carpel are considered.

Carboniferous Productidina and Chonetidina of the Cantabrian Mountains (NW Spain): Systematics, stratigraphy and palaeoecology

Abstract: The Carboniferous sediments of the thrust structures between the Porma and Bernesga rivers (map 2) and the headwaters of a tribuary of the Luna River (map 3) are described. In the lithostratigraphic chapter, the Vegamian, Alba, Escapa and San Emiliano formations are described, ranging in age from the Tournaisian to the lowermost Westfalian. The Alba and Escapa formations are subdivided into three and two members, respectively. An attempt has been made to reconstruct the palaeoecological conditions during sedimentation. The palaeoecological interpretation is based mainly on the productoids and chonetoids, but other palaeontological and lithological evidence has also been used. Many faunal assemblages have been found, which are comparable to those described by Moore (1964) from Pennsylvanian and Permian deposits in Kansas (U.S.A.). A short sedimentary history is given in chapter IV. A systematic study has been made of the Carboniferous representatives of two suborders of the phylum Brachiopoda: the Productidina and the Chonetidina. 22 Genera of the Productacea are described. They are represented by 51 species and subspecies, three of which are new. The new species are Levipustula breimeri, Karavankina rakuszi and K. wagneri. Twelve species and subspecies of seven different genera are described from the family Chonetidae. The investigation of these brachiopods resulted in a reappraisal of the Spanish Carboniferous productoids and chonetoids, combined with the description of a number of elements previously unknown in Spain. The genus Karavankina is described in some detail since only a short introductory note (Ramovs, 1966) has been published previously. A pedicle sheath is described for the first time for the genus Chonetipustula. The groove in the internal moulds of small pedicle valves of that genus are shown to be due to a groove anterior to the pedicle sheath, and not to a median septum as supposed by previous authors. A comparison of the faunas with those of other areas leads to some interesting conclusions. The fauna of the Vegamian Formation is closely comparable with German faunas of a slightly younger, distinctly Visean age. The fauna appears to be dependent on the type of sediment deposited, viz. black shales, and not so much on the stratigraphic age. Van Ginkel (1965b) has dated the top of the Escapa Formation on the basis of fusulinids as Lower Bashkirian. The productoid assemblage of these deposits is unique and consists mainly of forms found in the Visean of north-western Europe, together with a few genera and species known from Moscovian and even younger strata elsewhere. The upper Bashkirian and the lowermost Moscovian faunas in Spain become more cosmopolitan, the Visean and Namurian elements being replaced by new ones. In Moscovian strata, it is found that the fauna shows close relationships with the faunas described from Russia and China as well as with those found in the Westfalian marine bands of north-western Europe. The Carboniferous faunas in nord-west Spain apparently belong to the Europe Tian-Shan faunal province, because the productoid fauna as well as the fusulinid fauna agree with those described for this province (Einor et al., 1965). It seems that Karavankina should be added as another characteristic genus for this faunal province. It occurs from the Cantabrian Mountains to China. The Kasimovian productoids belong to the Moscovian genera, but differ at a specific level.

Stratigraphy and Petrology of the Mainly Fluviatile Permian and Triassic Beacon Rocks, Beardmore Glacier Area, Antarctica

Abstract: The near horizontal Beacon strata (Devonian?-Triassic) of the Beardmore Glacier area rest on a peneplain cut mainly in a Precambrian to Lower Paleozoic graywacke and phyllite sequence intruded by granitic plutons. The 2600-m-thick Beacon sequence comprises eight formations; the Alexandra Formation (Devonian?), the Pagoda, Mackellar, Fairchild and Buckley Formations (Permian), the Fremouw and Falla Formations (Triassic), and the Triassic?-Jurassic Prebble Formation. The Ferrar Group (Jurassic), which overlies and intrudes the Beacon rocks, c~n­ prises the Kirkpatrick Basalt and Ferrar Dolerite. This study is concerned mainly with the stratigraphy and petrology of the Permian and Triassic Beacon strata above the glacial Pagoda Formation. The Mackellar Formation, which conform.ably overlies the Pagoda Formation, consists of 60 to 140 m of laminated mediumto dark-gray shale and light-gray fine-grained sandstone, but the proportion of sandstone increases to the northwest. Current flow was southeasterly. The formation was deposited in a quiet body of water extending for 1000 km along the Transantarctic Mountains from the Queen Elizabeth Range to the Ohio Range; Sr87/Sr86 ratios suggest a noimlarine enviroimlent. The Fairchild Formation consists of 130 to 220 m Qf arkosic sandstone deposited by southeast-flowing streams. The sand was derived from a granitic and metasedimentary source, though same may have been reworked glacial debris. The Buckley Formation is a crudely cyclic coal-bearing sequence about 750 m thick; sandstone beds rest on erosion surfaces and grade upward into carbonaceous shale. Coal forms as much as six percent of the section. Leaves (mainly Glossopteris) and stems are carmnon. Buckley sandstone had two nonvolcanic sources; quartz plagioclase K-feldspar sand from the west, and quartz-plagioclase sancl. from the north. Intermediate-acid volcanic detritus appears 100-300 m above the base of the formation and dominates the sandstones in the upper part. The Triassic Fremouw Formation consists of three parts: the lowest is a 100-m-thick cyclic sequence of quartzose sandstone and greenishgray siltstone; the middle, 200 m thick, is mainly siltstone and includes sandstone with volcanic fragments; the upper 300 mis mainly similar volcanic sandstone, although the beds become carbonaceous toward the top. A labyrinthodont jawbone fragment was discovered near the base of the formation, and leaves of Dicroidium and logs were found near the top; root impressions occur throughout. The Falla Formation, which is from 160 to 530 m thick, is a cyclic sandstone-shale sequence in the lower part. The sandstone is more

Saccate Plant Microfossils from the Permian of Western Australia

Abstract: Systematic descriptions of saccate plant microfossils from the northern Perth Basin are given. Twenty-nine species are described, five of which are new. Three new combinations are proposed. The stratigraphic distribution of each species is given.

Sedimentology, paleoclimatology, and diagenesis of Post-Hercynian continental deposits in the South-Central Pyrenees, Spain

Abstract: The first chapter of the post-Hercynian geologic history of the South-Central Pyrenees is recorded in a sequence of fluvial and volcanic deposits which reach a total of added maximum thicknesses of more than 2300 m and date from the Westphalian D up to and including the Lower Triassic The present study concerns the primary lithology, paleocurrents, depositional environment, paleoclimatology, and diagenesis of these deposits Five formations are distinguished: (5) Bunter Formation (Lower Triassic) (4) Peranera Formation (Permian) (3) Malpas Formation (Stephanian) (2) Erill Castell Volcanics (Stephanian?) (1) Aguiro Formation (Westphalian D) The deposits of the Aguiro Formation are the fills of fossil valleys forming part of a pronounced paleorelief The formation consists largely of conglomerates deposited by braided streams One level, near Aguiro, contains coal-bearing, tuffaceous mudstone and tuff beds, the environment of deposition corresponding to that of a back-swamp Most clastic components, many of wich are non-calcareous phyllite grains, can be recognized as stemming from the Paleozoic basement (Axial Zone of the Pyrenees, lying to the North of Aguiro) The Erill Castell Volcanics, consisting of silicified and kaolinized andesitic tuffs and one intercalated basaltic andesite sheet, were deposited on a hilly land surface, since they locally overly fossil slope breccia and contain some fluvial channel-fills The tuffs show evidence of penecontemporaneous pedogenesis The Malpas Formation contains

Microtextures in recent and fossil caliche

Abstract: Microtextures of calcite in recent caliche are similar to those of authigenic calcite in Upper Carboniferous, Permian and Lower Triassic continental sandstones and mudstones in the South-Central Pyrenees, Spain. Except for one profile in the Permian, no complete caliche profiles containing calcrete occur in the ancient deposits. It is suggested that the fossil authigenic calcite crystallized in early stages of diagenesis under climatic conditions favourable to the development of caliche.

Age of the Separation of South America and Africa

Abstract: ON the basis of the positions of the magnetic south pole in the Triassic determined by palaeomagnetic studies of African and South American rocks, Creer1 has argued that the drifting apart of Africa and South America began in the Permian. Briefly, if South America and Africa are placed in such a position that their Palaeozoic polar wandering curves coincide, there is obtained a reconstruction very similar to that suggested by the shapes of the coastlines, and the earliest palaeopoles which do not coincide are those of the Triassic. In this argument, the Triassic palaeopole for South America was computed from a study of the lavas of the Serra Geral formation, in the southern part of Brazil. Unfortunately, a radiometric study2 of forty-one samples of basalt and dacite has shown that the principal phase of this igneous cycle is of Middle Cretaceous age, about 115–125 m.y.

Saline ground-waters in the Carboniferous Rocks of the English East Midlands in relation to the geology

Abstract: Summary The Carboniferous system in the East Midlands is comprised of a limestone-shale series or a massive limestone (the Carboniferous Limestone) overlain by a cyclic sequence of sandstones, mudstones, seat-earths and coals (the Millstone Grit and Coal Measures). The geology is described briefly and modifications are made to correlations of the Millstone Grit and Lower Coal Measures in the light of recent studies of information obtained by deep drilling for oil. Most of the Carboniferous ground-waters discussed are saline with total concentrations ranging up to 246 000 mg/1. The concentration in all formations increases from the Eakring-Kelham Hills area towards Gainsborough, that is from SW to NE, and the variation in ionic content associated with this increase is discussed. The ground-waters are believed to have originated from the diagenesis of Carboniferous marine and brackish waters and possibly some Permian marine waters. They have probably been concentrated by argillaceous beds acting as semi-permeable membranes and it is suggested that the increase in the Ca/Cl and Mg/Cl ratios as the total ionic concentration increases is due to the selective concentration of calcium and magnesium ions by argillaceous beds. In the south-west and south of the East Midlands the saline water has been diluted, probably by meteoric water moving through the aquifers from the outcrop areas and discharging into Permo-Triassic rocks, where these overlie Carboniferous aquifers at depth in the south-east of the region.

Permo-Triassic Section in Central Iran: GEOLOGICAL NOTES

Abstract: An exceptionally thick and very fossiliferous Upper Permian-Lower Triassic marine transitional sequence has been discovered in the Abadeh region of Central Iran. The uppermost Permian of this section compares closely with the classic Julfa (FOOTNOTE 3) section, the stratotype of the latest Permian Dzhulfian (FOOTNOTE 4) Stage, which is about 1,100 km (683 mi) northwest of Abadeh. The Abadeh section, however, is thicker and possibly more complete than the Julfa section.

Permian Evaporites in North Sea Basin

Abstract: Thick evaporite beds are present in the Permian beneath the North Sea, and can be correlated with the known successions in Germany and in England. The evaporites are more widespread in the upper division (Zechstein) than in the lower (Rotliegendes). This paper concerns chiefly the Zechstein of the English side of the basin, in which four main evaporite cycles are present. Zechstein salt movement began near the end of the Early Triassic when the overburden was only about 2,000 ft (610 m) thick, and continued throughout the Mesozoic and Tertiary. Movement was earlier in the west than in the east. Salt plugs are associated particularly with the margins of a large NNW-SSE trough which became fully developed during the Jurassic. Important structural features and thickness changes in the Mesozoic and Tertiary rocks were caused by the salt movement, and are almost entirely compensated by salt at depth. As a result, the base of the Permian is nearly parallel, on a regional scale, with the base of the Quaternary though separated from it by about 10,000 ft (3,000 m) of moderately complicated strata.

Xenodiscacean ammonoids and their bearing on the discrimination of the Permo-Triassic boundary

Abstract: Xenodiscacean ammonoids from Dzhulfa in Soviet Transcaucasia, assigned to Tompophiceras, Bernhardites and Paratirolites, have been interpreted as indicating that the enclosing beds, which also contain tetracorals, productacean brachiopods and goniatites, are Lower Triassic. Critical examination of the identifications shows that these beds should be regarded as Permian, not Triassic. Tompophiceras and Bernhardites are based on Triassic type species but the specimens from Dzhulfa are not demonstrably congeneric. Interpretation of Tompophiceras as a genus with a fastigate venter is rejected. Paratirolites, previously regarded as Triassic, is evidently Permian, and is now recorded from Madagascar, this being the first record outside Transcaucasus. New evidence is presented concerning the exact age of Glyptophiceras. The Dzhulfa section has been interpreted as providing a continuous transition, in the marine facies, between beds of Permian and Triassic age. This interpretation is rejected. It remains probable that there are no sections, in any part of the world, that do so.

Marine Paleozoic Rocks of Mexico

Abstract: Rocks of all Paleozoic systems are present in Mexico and, from north to south, are distributed in several basins: Sonora-Pedregosa basin (including the postulated Palomas-Villa Ahumada platform), Chihuahua basin, main Paleozoic geosyncline and Tlaxiaco subbasin, and Chiapas-Guatemala basin. The maximum known thickness of Paleozoic strata is estimated to be about 3,500 m. Data are too few to make reliable and detailed isopach and lithofacies maps of the Mexican Paleozoic. Sections studied and measured to date indicate that, of all the systems, the Silurian is the most poorly represented. Early Devonian strata are unknown. The Cambrian and Ordovician Systems are developed best in northern Mexico, but fossiliferous Cambrian, Ordovician, and Carboniferous strata recently were discovered for the first time in Oaxaca, southern Mexico. The Mississippian, Pennsylvanian, and Permian are the most widespread Paleozoic systems. Most Paleozoic rocks in which fossils are preserved were deposited in shallow-water environments. Deeper water lithofacies have been found in strata of middle and late Paleozoic ages, and their predominance in eastern Mexico suggests that the seas of those times were open toward the Gulf of Mexico. The paleogeographic maps show the relations between the basins and platforms of the southern United States and their equivalents in northern Mexico. Paleozoic strata are drilling objectives in some areas of Mexico, particularly in the north-central part.

Stratigraphy of the Permian and Lower Triassic marine sediments of the Gympie District, Queensland

Abstract: Six formations are recognised within the 10,000 feet of Permian and Lower Triassic marine sediments exposed in the Gympie district of southeast Queensland. In superpositional order these have been named the Highbury Volcanics, Rammutt Formation, South Curra Limestone, Tamaree Formation, Keefton Formation, and Traveston Formation. A low angle unconformity appears to occur at the base of the Keefton Formation and the available palaeontological data suggest that this unconformity embraces the Permian-Triassic boundary. Rich marine faunas occur in the Rammutt Formation, lower and upper parts of the South Curra Limestone, and in the upper part of the Traveston Formation. The faunas of the Rammutt Formation and lower part of the South Curra Limestone are similar and can be correlated with Fauna II of Dickins (Dickins et al., 1964) in the Bowen Basin. They are probably of lower Artinskian (Aktastinian) age. A different fauna from the upper part of the South Curra Limestone is correlated with Fauna IV of Dickins and is therefore probably of basal Upper Permian age. An ammonoid fauna from the upper part of the Traveston Formation belongs to the middle Lower Triassic zone of Meekoceras gracilitatis. The "Kin Kin Phyllite" as mapped appears to overlie both Upper Permian and Lower Triassic rock units. Unfortunately it has not been possible to subdivide the Phyllite in the area studied because of its limited outcrop and lithological homogeneity.

Paleomagnetism of Permian redbeds from the Colorado Plateau

Abstract: Partial thermal demagnetization of Permian sediments from two locations on the Colorado Plateau has, in some cases, isolated a thermally stable paleomagnetic direction that is significantly different from the results previously published for the Permian rocks of the southwestern United States. The stable magnetization was successfully recovered from samples of the Halgaito tongue of the Cutler formation, the Hoskinnini tongue of the Moenkopi (Triassic?) formation, the Toroweap formation, and the Hermit shale. The NRM of other formations, including the Supai, was found to be thermally unstable. Thermal demagnetization shows that a secondary component of magnetization parallel to the earth's present dipole field direction has probably been acquired by all the Permian sediments of this area.

Age of adularia and metamorphism, Ouachita Mountains, Arkansas

Abstract: Adularias from quartz veins give isotopic ages which bracket crystallization between 287 and 214 m.y. ago. A Middle Pennsylvanian age is excluded. Isotopic, stratigraphic, and structural data suggest deposition in Late Pennsylvanian or Early Permian and persistence of mild deformation and elevated temperatures related to low-grade regional metamorphism into and possibly somewhat after Middle Permian. The metamorphism may coincide with the 250 m.y. heating event in the southern Appalachians. Feldspar data suggest continuous Ar diffusional loss activated by very slow Al-Si ordering toward the stable structural state of maximum microcline. Feldspars in intermediate structural states are more prone to such ordering and give lower ages.

World correlations of New Zealand Permian stages

Abstract: New Zealand Permian stages are discussed. Two horizons are recognised below the lowest formally named stage, and the Braxtonian Stage is subdivided into the Barrettian and Flettian substages. Recent advances in the Permian geology of Siberia, and work by the writer on huge collections from the Canadian Arctic, reveal that the pattern of stages proposed for New Zealand also holds true for the Arctic realm. A visit to Tasmania confirmed that the stages can also be recognised there, including a very high Permian fauna in the upper Ferntree beds, equivalent to the New Zealand Waiitian Stage. The persistence over much of the world of brachiopod and bivalve horizons suggests that more stress should be given to these groups in attempting world correlations for the Permian, and therefore correlations for New Zealand stages are adjusted accordingly, bringing the stages into harmony with some fusuline and ammonoid evidence, but conflicting with the views of some workers on fusulinids and ammonoids. Most of...