Lower Paleozoic Sandstone Research Articles

Early Carboniferous (Mississippian) intertwining sediment dispersal network across the Laurentian cratonic interior

Early Carboniferous (Mississippian) strata across the Laurentian cratonic interior record the transition from a stable carbonate platform, supporting a broad epicontinental sea, to a series of widespread, mixed carbonate-siliciclastic successions. As the southern terminal sink, the Mississippian succession preserved on the southern Midcontinent provides evidence and constraints for sediment dispersal patterns. This paper presents the first comprehensive U–Pb detrital-zircon geochronological record of all known Mississippian sandstones from the southern Ozark Dome of southern Missouri and northwestern Arkansas. This study identifies the provenance of these Mississippian sandstones and establishes their sediment dispersal networks across the cratonic interior. Results show that a major provenance shift occurred between Lower and Upper Mississippian strata. The Lower Mississippian Bachelor Sandstone was sourced from the Laurentian craton, while Upper Mississippian and basal Pennsylvanian sandstones were sourced through recycling of upper Proterozoic and lower Paleozoic sandstones within the Laurentian craton to the north, the unroofing of the Appalachian orogenic belt from the east-northeast, and potentially some direct contribution from uplifted Precambrian basement along the Transcontinental Arch to the northwest. By combining previously published detrital zircon data from Laurentia, we propose that the Mississippian sedimentation reflects an intertwining dispersal system associated with multiple sources. Sediments derived from all three potential sources were merged and transported southward across Laurentia.

Material composition and formation conditions of lower Paleozoic sandstones of Engane-Pe Ridge (Polar Urals)

The paper presents the results of the study of the material composition of Upper Cambrian-Lower Ordovician Manitanyrd sandstones series in the southern part of Engane-Pe Ridge (Polar Urals). The study of the lithological and geochemical characteristics of feldspar-quartz sandstones has confirmed their formation in a shallow-water basin at the passive continental margin in a cold climate. An episode of volcanic activity, associated with the epicontinental riftogenesis, resulted in the appearance of a sub-comformable body of ultra-potassium basaltoids, and at a distance from it, there is a sandstone horizon containing "concretion" formations. In the composition of the sandstones there is a slightly altered volcanomictic material but they lack of recycled fragments and redeposited material of the weathering crust. The petrochemical features of Manitanyrd sandstones do not allow expecting sedimentary gold mineralization in them.

Lower Paleozoic reservoir zonation into different flow units using turbulence factor and their relations to diagenesis

Surface Lower Paleozoic sandstone samples were collected from southeast central Sinai. These samples subjected to petrophysical measurements which are porosity and permeability. It is known that turbulence factor (β) is a good tool to describe turbulent flow level, hence it was used to detect the flow properties distribution that corresponds to the nature of the pore system, so turbulence factor (β) was correlated with porosity, permeability, and reservoir quality index using many equations, where porosity correlation shows the presence of three groups having same porosity ranges but correspond to different values of turbulence factor, this refers to the presence of different flow zones. Porosity–permeability relation confirmed also the presence of similar three groups, where there are nearly same porosity ranges but with different permeability values. Consequently, samples with nearly same porosity values and representing the three groups were selected for capillary pressure by mercury injection to reveal the flow properties that characterize each group. Capillary pressure results confirmed that each group has their own pore system and flow regime. Petrography was done by optical polarizing microscope (OPM) through thin sections. The results indicated that the studied sandstone is composed mainly of quartz arenite microfacies of fine, angular to subrounded, moderately well sorted monocrystalline quartz grains. There are several features indicating that the investigated sandstones have been subjected to diagenesis processes. Diagenetic events identified in these sandstones include considerable compaction during burial diagenesis at higher temperatures and low flow rates, cementation by clay minerals and iron oxides, dissolution and alteration of unstable clastic grains, and tectonically induced grain fracturing. Unstable clastic grains like feldspars suffered considerable alteration to kaolinite when exposed to meteoric water of low ionic strength near the surface. The distribution of this kaolinite rather than the post-depositional iron oxides in pores of the studied sandstone leaded to differentiating these sandstones into three different flow units. This zonation indicates that the turbulence properties are proportional to the diagenetic effects inside the pores.

Sedimentological Conditions of Early Paleozoic Paleobasin in the Northwestern Russian Platform: Reconstruction of Paleolithodynamics and Mineral Resources

Reconstruction of characteristics of sedimentary environments of the Lower Paleozoic Sandstone (hereafter LPS) sequence in the northwestern Russian platform based on granulometric and texture analyses reveals high paleohydrodynamic conditions of sedimentation which decrease to moderate in south-east direction. Determination of quantitative paleolithodynamic parameters showed that the real sedimentation duration was considerably less than the related stratigraphic scale interval that is evidence of long interrupt of sedimentation and re-deposition of the clastic material. Study of paleolithodynamics is significant both for reconstruction of the paleobasin history and assessment of mineral resources.

Varietal heavy mineral analysis of sediment provenance, Lower Cretaceous Scotian Basin, eastern Canada

The origin of a major increase in sand supply in the Early Cretaceous of the Scotian Basin, offshore eastern Canada, has been investigated by analysis of heavy mineral varieties. The chemistry of detrital minerals from the Scotian Basin was compared with that of minerals from potential source rocks, sampled from older sedimentary successions, river sands and glacial tills on land. Heavy mineral varieties were established based on > 1000 high quality electron microprobe (EMP) analyses and used to classify heavy mineral types by Mineral Liberation Analysis (MLA), which uses a rapid scanning electron microscope particle analyser. Heavy mineral varieties were compared between the Cretaceous quartz arenites and subarkoses and samples from potential source areas. Different chemical varieties of the same mineral group have different grain size distributions, so that their relative modal abundances may be influenced by hydraulic sorting, but modal abundance of different varieties of tourmaline, garnet and spinel provides useful information. Widely used provenance-sensitive mineral ratios are difficult to interpret because of the abundance of polycyclic sources. Comparisons of the shape parameters of the individual mineral types are also useful for provenance identification. Aspect ratio in elongate grains, such as tourmaline and zircon, is a measure of polycyclic reworking, but is influenced by the initial shapes of minerals from different source rocks. Uniformity of varietal heavy minerals over a large area and stratigraphic range, and the covariance of spinel and zircon with quite different crystalline sources, indicate predominance of polycyclic sources to the Central Scotian Basin, probably principally from Carboniferous and Lower Paleozoic sandstones, in part sourced from western Newfoundland ophiolites. Heavy mineral varieties in the West Scotian Basin can be closely matched to sources in the adjacent Meguma Terrane of the Appalachians. All the data show that the sands of the Scotian Basin were derived from reworking of crystalline basement of the Appalachian orogen and its Paleozoic sandstone cover, uplifted during rifting of Iberia from the Grand Banks. There is no evidence of a significant supply of sand to the Scotian Basin from a proto-St Lawrence River.

Tracing the position of the South China block in Gondwana: U–Pb ages and Hf isotopes of Devonian detrital zircons

U–Pb detrital zircon geochronology from Lower Devonian quartz arenites of the northwestern margin of the Yangtze block yields dominant early Neoproterozoic (0.85–1.0 Ga), Pan-African (0.5–0.65 Ga) and middle Neoproterozoic (0.68–0.8 Ga) age populations and minor Mesoproterozoic to middle Mesoarchean (1.0–3.0 Ga) ages. Middle Mesoarchean to Mesoproterozoic rocks, however, are widespread in the South China block. Although Hf isotopic compositions show both juvenile crustal growth and crustal reworking for all the age groupings, the crust growth, essentially mantle-derived, occurred mainly around 3.1 Ga, 1.9 Ga and 1.0 Ga, respectively. Zircon typology and youngest grain ages indicate that this suite of quartz arenites was the product of multiphase reworking. Abundant magmatic zircon detritus with concordant U–Pb Grenvillian and Pan-African ages, together with accompanying various ε Hf( t) values, indicate an exotic provenance for the quartz arenite external to the South China block. Qualitative comparisons of age spectra for the late Neoproterozoic sediments of the Cathaysian Block, early Paleozoic sediments of pre-rift Tethyan Himalaya sequence in North India and lower Paleozoic sandstone from the Perth Basin in West Australia, show that they all have two the largest age clusters representing Grenvillian and Pan-African orogenic episodes. The resemblance of these age spectra and zircon typology suggests that the most likely source for the Lower Devonian quartz arenites of the South China block was the East African Orogen and Kuunga Orogen for their early Grenvillian and Pan-African populations, whereas the Hannan–Panxi arc, Jiangnan orogen, and the Yangtze block basements might have contributed to the detrital zircon grains of the Neoproterozoic and Pre-Grenvillian ages. Hf isotopic data indicate that the crustal evolution of the drainage area matches well with the episodic crust generation of Gondwana. These results imply that the previously suggested position of the SCB in Gondwana should be re-evaluated, and the South China block should be linked with North India and West Australia as a part of East Gondwana during the assembly of Gondwana, rather than a discrete continent block in the paleo-Pacific.

Contribution of pre Pan-African crust to formation of the Arabian Nubian Shield: New secondary ionization mass spectrometry U-Pb and O studies of zircon

Research Article| October 01, 2009 Contribution of pre Pan-African crust to formation of the Arabian Nubian Shield: New secondary ionization mass spectrometry U-Pb and O studies of zircon Yaron Be'eri-Shlevin; Yaron Be'eri-Shlevin * 1Department of Geological and Environmental Sciences, Ben-Gurion University, Beer-Sheva, Israel 2Laboratory for Isotope Geology, Swedish Museum of Natural History, Stockholm, Sweden *E-mail: yaron.beeri@nrm.se. Search for other works by this author on: GSW Google Scholar Yaron Katzir; Yaron Katzir 1Department of Geological and Environmental Sciences, Ben-Gurion University, Beer-Sheva, Israel Search for other works by this author on: GSW Google Scholar Martin J. Whitehouse; Martin J. Whitehouse 2Laboratory for Isotope Geology, Swedish Museum of Natural History, Stockholm, Sweden Search for other works by this author on: GSW Google Scholar Ilka C. Kleinhanns Ilka C. Kleinhanns 3Geowissenschaftliches Zentrum der Universität Göttingen, Göttingen, Germany Search for other works by this author on: GSW Google Scholar Geology (2009) 37 (10): 899–902. https://doi.org/10.1130/G30206A.1 Article history received: 09 Mar 2009 rev-recd: 12 May 2009 accepted: 19 May 2009 first online: 03 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share MailTo Twitter LinkedIn Tools Icon Tools Get Permissions Search Site Citation Yaron Be'eri-Shlevin, Yaron Katzir, Martin J. Whitehouse, Ilka C. Kleinhanns; Contribution of pre Pan-African crust to formation of the Arabian Nubian Shield: New secondary ionization mass spectrometry U-Pb and O studies of zircon. Geology 2009;; 37 (10): 899–902. doi: https://doi.org/10.1130/G30206A.1 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGeology Search Advanced Search Abstract New secondary ionization mass spectrometry U-Pb and O isotope analyses of detrital zircons from the Sa'al schist in Sinai coupled with whole-rock Nd isotopic analyses provide new evidence of pre- Neoproterozoic crust in the northernmost Arabian-Nubian Shield (ANS). The detrital zircon age population is bimodal, with concordia ages of 1029 ± 7 Ma and 1110 ± 8 Ma. The whole-rock ϵNd(t = 1.0 Ga) value of +2 is significantly lower than found for juvenile Neoproterozoic rocks in the region. Thus, the Sa'al schist is interpreted to represent Kibaran (Grenville) age crust incorporated into the northernmost ANS. The δ18O (zircon) values (6.1‰–9.4‰) imply that supracrustal recycling was involved in the formation of this ca. 1.0–1.1 Ga crust. A compilation of reported xenocrystic and detrital pre-ANS zircons and the variability of Nd, Sr, Pb, and O isotopic compositions within the shield suggests that its northernmost and eastern margins were more strongly contaminated by older crust ca. 0.9–3.0 Ga old. The distribution of 0.9–1.1 Ga xenocrystic and detrital zircons mainly in the east and north of the ANS suggests that such crust characterized parts of the northeastern margin of western Gondwana prior to ANS formation, and that 0.9–1.1 Ga old zircons detected in lower Paleozoic sandstone cover may have a proximal provenance. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

Magmatism coeval with lower Paleozoic shelf basins in NW-Argentina (Tastil batholith): Constraints on current stratigraphic and tectonic interpretations

Abstract The Tastil batholith (Eastern Cordillera, NW Argentina) holds relevant keys for interpreting the tectonic evolution of the Central Andes basement since it has always been interpreted as the subcrop of the Cambrian and Lower Ordovician basins in the Eastern Cordillera. However, in the Angosto de la Quesera section, the batholith intrudes sandstones underlying a fossiliferous Lower Tremadocian conglomerate containing Tastil granite pebbles. The precise assignation of the sandstones intruded by the granite to Cambrian Meson Group or to the Uppermost Cambrian–Lower Tremadocian Santa Victoria Group is a key for refining the relationships between magmatic and sedimentary units. The ages of 526 Ma and 517 Ma (U/Pb, zircons) obtained from two facies of the batholith are coherent with the proposal of including these sandstones in the Meson Group. However, the lithologic features and fossil content point to an affinity with the basal units of the Santa Victoria Group according to sedimentologic and stratigraphic studies ruled out by other authors. The intrusive relationships between the Tastil batholith and the Lower Paleozoic sandstones indicates the batholith is coeval with the Meson and/or Santa Victoria groups basins instead of being its subcrop, which strongly contradicts previous proposals about basement evolution along the Lower Paleozoic margin of Gondwana. Therefore, the genesis and emplacement of the Tastil batholith must be related to the development of the Lower Paleozoic shelf basins rather than with the final stages of Puncoviscana-type basin evolution. The basement of central and northern Argentina records a wide spectrum of sedimentary, deformational, magmatic and metamorphic processes at a variety of crust levels during the Early Paleozoic. Tastil batholith emplacement and exhumation in the Eastern Cordillera represent shallower crustal expressions of the plutonic and high-T–low-P metamorphic events at deeper levels in the basement now exposed mainly in eastern Puna and Pampean Ranges.

Petrography and geochemistry of lower Paleozoic sandstones, East Sinai, Egypt: Implications for provenance and tectonic setting

Petrography, mineralogy and chemical analyses were combined to investigate the lower Paleozoic sandstones at Wadi El-Quseiyeb area, East Sinai. They are mainly classified texturally as silty sandstones, sandstones and clayey siltstone. Their average modal composition (QFL, 87:11:2), classifies them as quartz arenite and arkosic arenite, with high proportions of quartz, monocrystalline quartz grains, more potash feldspar than plagioclase and a low plagioclase/total feldspar ratio ( P/ F < 0.2). High SiO 2, K 2O > Na 2O, and low Fe 2O 3 + MgO values revealed by chemical analyses are consistent with the modal data. Other criteria include elevated Ba and Sr contents and depletion in the ferromagnesian elements. The petrography and geochemistry suggest a stable continental (passive) margin or intracratonic basin, analogous to that of an Atlantic-type continental shelf. Also, they reflect a stable craton interior source, devoid, to a large extent, of basic debris and ultimately derived from a low-lying granite-rich Precambrian craton. Chemical index of alteration (CIA) and the Plagioclase index of Alteration (PIA) values range from 57.2 to 93.0 and from 79.7 to 94.6, respectively. However, most samples have values more than 60, suggesting a moderate to relatively high degree of alteration (weathering) in the source area.

Detrital zircon U–Pb geochronology of Cryogenian diamictites and Lower Paleozoic sandstone in Ethiopia (Tigrai): Age constraints on Neoproterozoic glaciation and crustal evolution of the southern Arabian–Nubian Shield

Detrital zircon geochronology of Neoproterozoic diamictites and Ordovician siliciclastics in northern Ethiopia reveals that the southern Arabian–Nubian Shield (ANS) formed in two major episodes. The earlier episode at 0.9–0.74 Ga represents island arc volcanism, whereas the later phase culminated at 0.62 Ga and comprised late to post orogenic granitoids related to crustal differentiation associated with thickening and orogeny accompanying Gondwana fusion. These magmatic episodes were separated by about ∼100 my of reduced igneous activity (a magmatic lull is detected at about 0.69 Ga), during which subsidence and deposition of marine carbonates and mudrocks displaying Snowball-type C-isotope excursions (Tambien Group) occurred. Cryogenian diamictite interpreted as glacigenic (Negash synclinoria, Tigrai) and polymict conglomerates and arkose of possible peri-glacial origin (Shiraro area, west Tigrai), deformed and metamorphosed within the Neoproterozoic orogenic edifice, occur at the top of the Tambien Group. They were formed well after the shutdown of island arc igneous activity in this region and are pierced by the post-collision granitoids. Negash diamictite and Shiraro sequence contain detrital zircons derived from underlying ∼0.85–0.74 Ga volcanics, a small number of 1.1 Ga zircons (likely inherited within the underlying arc crust) were also detected. The youngest detrital zircons in these sequences are 0.75 and 0.74 Ga. A broadly Sturtian timing (i.e. ∼0.70 Ga) is plausible, but we note this is a lower time limit. Our investigation shows that clasts in the diamictite have a proximal provenance and are derived from underlying igneous rocks and metasediments (including Tambien carbonates). Diamictites were formed when subsidence and basin sedimentation ceased and the Tambien and its underlying igneous complex (Tsaliet Group) were uplifted and eroded (incision exceeded 1500 m). Thus, although bearing the hallmark of a Snowball Earth, the properties of Tambien diamictites indicate relief differentiation and vertical motions may have played a significant role in shaping the glacial record of the southern ANS.

Impact-generated carbonate melts: evidence from the Haughton structure, Canada

Evidence is presented for the melting of dolomite-rich target rocks during formation of the 24 km diameter, 23 Ma Haughton impact structure on Devon Island in the Canadian high Arctic. Field studies and analytical scanning electron microscopy reveal that the >200 m thick crater-fill deposit, which currently covers an ∼60 km2 area in the center of the structure, comprises fragmented target rocks set within a carbonate–silicate matrix. The silicate component of the matrix consists of Si–Al–Mg-rich glass. The carbonate component is microcrystalline calcite, containing up to a few wt% Si and Al. The calcite also forms spherules and globules within the silicate glass, with which it develops microtextures indicative of liquid immiscibility. Dolomite clasts exhibit evidence of assimilation and may show calcite and rare dolomite overgrowths. Some clasts are penetrated by calcite and silicate injections. Along with the carbonate–silicate glass textures, the presence of pigeonite and spinifex-textured diopside suggests that the matrix to the crater-fill deposit was originally molten and was rapidly cooled. This indicates that the impact event that generated Haughton caused fusion of the predominantly dolomitic target rocks. It appears that the Ca–Mg component of the dolomite may have dissociated, with Mg entering the silicate melt phase, while the Ca component formed a CaCO3-dominant melt. The silicates were derived by the fusion of Lower Paleozoic sandstones, siltstones, shales and impure dolomites. Evidence for melting is corroborated by a review of theoretical and experimental work, which shows that CaCO3 melts at >10 GPa and >2000 K, instead of dissociating to release CO2. This work indicates that carbonate-rich sedimentary targets may also undergo impact melting and that the volume of CO2 released into the atmosphere during such events may be considerably less than previously estimated.

Provenance record of a rift basin: U/Pb ages of detrital zircons from the Perth Basin, Western Australia

Abstract U/Pb dating of 588 detrital zircons by ion microprobe from Lower Triassic, Permian and lower Paleozoic sandstone samples from the Perth Basin yield ages ranging from Archean to early Paleozoic. The detrital age spectrum of Lower Triassic samples differ from underlying units in lacking Archean and post-Mesoproterozoic detritus. The Archean Yilgarn craton has previously been envisaged as the main source of detritus in the Perth basin. The bulk of the detritus, however, is of Mesoproterozoic age, which together with the overall broad spectrum of age ranges within individual samples indicates that the detritus was derived from multiple sources. Potential source regions recognized include the Yilgarn craton, the Mesoproterozoic Albany Fraser Orogen, the Meso- to Neoproterozoic Leeuwin complex of the Pinjarra orogen, and probably also the late Mesoproterozoic Northampton complex of the Pinjarra orogen. In addition, source terranes possibly associated with Greater India and East Antarctica, which originally formed the western and southern margins of the basin, may have also contributed detritus accounting for the input of material whose age cannot be related to the known age ranges in currently exposed bounding source blocks. The multi-sourced nature of the detritus suggests the Perth basin was not a simple half-graben structure down stepping to the west but contained a variety of uplifted blocks with an overall longitudinal supply of detritus from the south. The distribution of exposed source blocks changed dramatically at the start of the Triassic with the cessation of input from Archean and Neoproterozoic source regions. The differing age spectra between Triassic and Permian strata and between Late Permian and older sequences suggest any reworked detritus is of extra-basinal origin and not related to intra-basin erosion of underlying rock units. Potential sources for this reworked multicycle detritus are the metasedimentary sequences within the bounding source terranes.

Origin of a classic cratonic sheet sandstone: Stratigraphy across the Sauk II–Sauk III boundary in the Upper Mississippi Valley

Research Article| February 01, 1998 Origin of a classic cratonic sheet sandstone: Stratigraphy across the Sauk II–Sauk III boundary in the Upper Mississippi Valley Anthony C. Runkel; Anthony C. Runkel 1Minnesota Geological Survey, 2642 University Avenue, St. Paul, Minnesota 55114-1057 Search for other works by this author on: GSW Google Scholar Robert M. McKay; Robert M. McKay 2Iowa Department of Natural Resources, Geological Survey Bureau, 109 Trowbridge Hall, Iowa City, Iowa 52242-1319 Search for other works by this author on: GSW Google Scholar Allison R. Palmer Allison R. Palmer 3Institute for Cambrian Studies, 445 North Cedarbrook Road, Boulder, Colorado 80304-0417 Search for other works by this author on: GSW Google Scholar GSA Bulletin (1998) 110 (2): 188–210. https://doi.org/10.1130/0016-7606(1998)110<0188:OOACCS>2.3.CO;2 Article history first online: 01 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Anthony C. Runkel, Robert M. McKay, Allison R. Palmer; Origin of a classic cratonic sheet sandstone: Stratigraphy across the Sauk II–Sauk III boundary in the Upper Mississippi Valley. GSA Bulletin 1998;; 110 (2): 188–210. doi: https://doi.org/10.1130/0016-7606(1998)110<0188:OOACCS>2.3.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGSA Bulletin Search Advanced Search Abstract The origin of cratonic sheet sandstones of Proterozoic and early Paleozoic age has been a long-standing problem for sedimentologists. Lower Paleozoic strata in the Upper Mississippi Valley are best known for several such sandstone bodies, the regional depositional histories of which are poorly understood. We have combined outcrop and subsurface data from six states to place the Upper Cambrian Wonewoc (Ironton and Galesville) Sandstone in a well-constrained stratigraphic framework across thousands of square kilometers. This framework makes it possible for the first time to construct a regional-scale depositional model that explains the origin of this and other cratonic sheet sandstones.The Wonewoc Sandstone, although mapped as a single contiguous sheet, is a stratigraphically complex unit that was deposited during three distinct conditions of relative sea level that span parts of four trilobite zones. During a relative highstand of sea level in Crepicephalus Zone time, quartzose sandstone lithofacies aggraded more or less vertically in nearshore-marine and terrestrial environments across much of the present-day outcrop belt around the Wisconsin arch. At the same time, finer grained, feldspathic sandstone, siltstone, and shale aggraded in deeper water immediately seaward of the quartzose sand, and shale and carbonate sediment accumulated in the most distal areas. During Aphelaspis and Dunderbergia Zones time a relative fall in sea level led to the dispersal of quartzose sand into a basinward-tapering, sheet-like body across much of the Upper Mississippi Valley. During early Elvinia Zone time a major transgression led to deposition of a second sheet sandstone that is generally similar to the underlying regressive sheet.The results of this investigation also demonstrate how subtle sequence-bounding unconformities may be recognized in mature, cratonic siliciclastics. We place the Sauk II-Sauk III subsequence boundary at the base of the coarsest bed in the Wonewoc Sandstone, a lag developed through erosion that occurred during the regional regressive-transgressive event that spanned Aphelaspis to early Elvinia Zones time. Such sequence-bounding unconformities are difficult to recognize where they are contained within coarse siliciclastics of the Upper Mississippi Valley, because they separate strata that are texturally and mineralogically similar, and because erosion occurred on a loose, sandy substrate along a low, uniform gradient, and in a nonvegetated terrestrial environment. Furthermore, the ultramature mineral composition of the exposed substrate is resistant to the development of a recognizable weathering profile.The well-known sheet geometry of the Wonewoc and other units of lower Paleozoic sandstone of this area is not dependent on atypical terrestrial depositional conditions conducive to the widespread distribution of sand, as commonly believed. Sand was spread into a sheet dominantly within the marine realm in a manner similar to that inferred for many better-known sandstone bodies deposited in the North American Cretaceous Western Interior seaway and Tertiary Gulf of Mexico. The laterally extensive, thin character of the Upper Mississippi Valley sandstone bodies compared to these other sandstone bodies simply reflects deposition of a continuously abundant supply of sand on a relatively stable, nearly flat basin of slow, uniform subsidence during changes in sea level. The dearth of shale in this and other cratonic sandstones can be indirectly attributed to the same controls, which led to an uncommonly low preservation potential for fairweather deposits on the shoreface. This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

Provenance and plate tectonic indexing of lower Paleozoic sandstones, Quebec and Maine; discussion and reply

Provenance and plate tectonic indexing of lower Paleozoic sandstones, Quebec and Maine; discussion and reply

Provenance and plate tectonic indexing of lower Paleozoic sandstones, Quebec and Maine

Provenance and plate tectonic indexing of lower Paleozoic sandstones, Quebec and Maine

Precambrian zircons from the Florida basement: A Gondwanan connection

A Gondwanan origin for the pre-Cretaceous basement of Florida is suggested by U- Pb ages of 515 to 2860 Ma for single zircons separated from subsurface samples of lower Paleozoic sandstone of the Suwannee basin (Alachua County, Florida) and Neoproterozoic Osceola granite (Osceola County, Florida). Forty individual grains analyzed by SHRIMP ion microprobe yielded ages from 515 to 2860 Ma; ages >1000 Ma were predominantly concordant. Two principal populations are evident: (1) 515 to 637 Ma (avg. = 574 Ma; 206 Pb/ 238 U ages) and (2) 1967 to 2282 Ma (avg. = 2130 Ma; 207 Pb/ 206 Pb ages). Only six zircons were recovered from the granite; four are Pan-African and two are Archean. For the sandstone, the similarity between the Sm-Nd model age (1245 Ma) and the average of the single zircon ages (1326 Ma) suggests that these zircons are chronologically representative of the aggregate provenance of the sandstone. The two dominant zircon age groupings correspond chronologically to the Pan-African and Birimian or Eburnian (Africa) and to the Brasiliano and Trans-Amazonian (South America) orogenic cycles. The presence of detritus from rocks of these two orogenic cycles clearly places the basement of Florida in Gondwanaland proximal to the West African and/or Trans-Amazonian-San Luis cratons in the early Paleozoic, a location it probably shared with other circum-Atlantic exotic terranes (Avalonian, Cadomian, and/or Carolina).

Significance of Carbonate-Clastic Shoaling Cycles in Mississippian of Northern Arkansas: ABSTRACT

Shoaling-upward carbonate shelf cycles are known to occur in many parts of the world and throughout the geologic record. A typical shoaling carbonate cycle begins with deep-shelf, interbedded, lime mudstones and shale. These are succeeded by open-shelf bioclastic packstones and grainstones, and finally in many places by oolite, the latter representing the culmination of the shoaling process. Subsequent cycles repeat this basic pattern. When correlated across a shelf, the cycles are thought to represent the episodic progradation of a carbonate sand platform that built up to wave base, subsided, and built up again. Upper Mississippian (Chesterian) strata in northern Arkansas consist of alternating limestones and shales that include a set of shoaling-upward cycles. These cycles, occurring within the dominantly carbonate Pitkin Formation, differ from the pattern described above in that they contain a significant terrigenous component. This material exists both as fissile black shale within lower-cycle lime mudstone, and as quartz sand admixed within upper-cycle oolite grainstones. This dual occurrence is thought to be related to movement of the shoreline that accompanied the repeated outbuilding of a carbonate platform. At the beginning of a cycle, the shoreline was distinct from the deeply submerged shelf and lime and terrigenous mud accumulated in a quiet-water setting. Thickness and facies anal sis of the Pitkin indicate an east-west trending shelf with a shoreline located in southern Missouri, perhaps curving south around the Ozark uplift. Eastward increase in shale percentage in the Pitkin suggests transport of fine clastics around the southeast flank of this uplift. The Illinois basin was an active Chesterian depocenter and during periods of maximum transgression fine clastics may have passed through a seaway southwest into northern Arkansas. As shoaling proceeded, the shoreline regressed south with the advancing carbonate sand sheet, cutting off the avenue of fine clastics. Quartz sand, probably derived from a thick sequence of lower Paleozoic sandstones exposed along the uplift by the retreating sea, became admixed with oolite across the newly built platform. These shoalin cycles are the product of slow, steady, subsidence along a northern Arkansas shelf punctuated by episodes of relatively rapid carbonate sand sedimentation and clastic influx. A similar tectonic and depositional setting must have given rise to other such deposits that occur in the geologic record. End_of_Article - Last_Page 453------------

A discussion on the structure and evolution of the Red Sea and the nature of the Red Sea, Gulf of Aden and Ethiopia rift junction - Eastern margin of the Red Sea and the coastal structures in Saudi Arabia

Results of many investigations since 1950 show that the eastern margin of the Red Sea and associated coastal structures in Saudi Arabia have a long geologic history, starting with the deposition of Precambrian eugeosynclinal sedimentary and volcanic rocks before 1000 Ma ago and extending to recent geologic time. The northeastern flank of the Red Sea rift valley is in a shield area affected by possibly four plutonic events at 1000, 720 to 735 (?), 660 to 670, and about 570 Ma. Cratonization of the shield occurred during all or part of the span 520 to 590 Ma. Nubian-type sandstone of Cambrian and Ordovician age laps up on the shield from Jordan southeastward around the rim of the Great Nafud basin, and along the eastern edge of the shield southeastward to 45° E longitude where it is overlapped by Permian limestone. The sandstone reappears to the south and extends southward and westward to the Asir Mountains at the Yemen border. Isolated sandstone outliers are present in the central shield, proving that lower Paleozoic sandstone covered most, if not all, of the basement as now exposed. The Mesozoic era was almost entirely a time of uplift and non-deposition except a middle to late Jurassic fringe marine invasion in the south and a possible narrow invasion from the Gulf of Suez at the end of the era. Marine and non-marine sedimentary deposits of middle and late Tertiary age are found along the Red Sea coast, and Oligocene basaltic flows are present at both low and high altitudes in the coastal ranges. Evidence for important volcanism during Oligocene and earliest Miocene time is widespread, and within the eastern rift fault zone early Miocene hypabyssal intrusives cut the shear zones. Major rifting occurred just before or during early Miocene when the flanks of the rift valley were ramped upward. Shortly after this volcanism a thickness on the order of 3500 m of middle Miocene marl and evaporite beds filled the Red Sea trough. Evidence also exists for widespread subaerial erosion in the Pliocene. Younger lava flows are Pliocene in age but the youngest, near Al Medinah, came as late as A. D. 1250. Lake-bed deposits are very probably in large part Pliocene throughout the shield. The Red Sea coastal plain in Saudi Arabia rises gently eastward from a 3 m littoral surface, generally underlain by dead reef from the Yemen border northward to Al Wajd, a distance of 1400 km. At Jizan, in the south, a salt dome has pushed the 3 m surface up to an elevation of about 50 m. From Al Wajd northward, Pleistocene terraces have been faulted, culminating in several surfaces as high as 520 m above the Red Sea at Tiran Island. Ramping of major fault-bounded blocks along the eastern side of the Red Sea trough—the Midian block in the north, a poorly defined central block, and the Asir block in the south—is connected with renewed movement on regional Precambrian faults. Drainage patterns of wadis in these blocks are characteristically affected by the ramping, and stream capture is common in the Midian and Asir blocks.

Stratigraphic and Tectonic Framework of Libya: ABSTRACT

Libya is situated on the unstable Mediterranean foreland of the African shield. Marine strata of Paleozoic, Mesozoic, and Cenozoic ages abound in northern Libya, but continental rocks of Paleozoic and Mesozoic ages predominate in southern Libya. Several marine incursions, mainly in Silurian, Middle Devonian, Carboniferous, Late Cretaceous, and Eocene times, reached far into the country, some crossing the southern border. Compression folds are almost wholly absent; however, uplift, subsidence, block faulting, and tilting have occurred, and angular and parallel unconformities are common. The major diastrophic disturbances include the Caledonian and Hercynian, as well as disturbances during Late Cretaceous and Oligocene through Miocene or Recent times. The chief regional structures are the Gefara-Gabese basin, Hamada basin, Gargaf arch, Marzuk basin, Tibesti-Haruj uplift, Kufra basin, north Cyrenaican uplift, and Sirte basin. Several large flows and intrusions of Cenozoic basalt and phonolite are present. Sand and gravel conceal the bedrock in about a third of the country. In the Sirte basin, marine sedimentation, differential compaction, reef development, subsidence, and block faulting, beginning in Late Cretaceous time, favored the development of source and reservoir rocks. Recoverable oil has been found chiefly in limestone and sandstone of Late Cretaceous and Tertiary ages, but also is reported in some knobs of lower Paleozoic sandstone and fractured Precambrian granite. In the Hamada basin, many oil accumulations have been found in sandstone beds of several Paleozoic systems. Most or all of the oil discovered to date probably is in anticlinal structures, but accumulations may exist in other types of traps. End_of_Article - Last_Page 608------------