Fossiliferous Chert Research Articles

Zur Paläontologie und Geologie fossilführender Hornsteine der S-Eifel (Oligozän, Rheinisches Schiefergebirge)

Zur Paläontologie und Geologie fossilführender Hornsteine der S-Eifel (Oligozän, Rheinisches Schiefergebirge)

Origin of Chert in Permian System in Southwestern Utah and Northwestern Arizona: ABSTRACT

Within the Permian System in southwestern Utah and northwestern Arizona, the Brady Canyon Member of the Toroweap Formation and the Fossil Mountain and Harrisburg Members of the Kaibab Formation contain five different forms of chert. These chert forms provide information about the origin and emplacement of chert in the Permian System. The forms present are: rounded chert nodules, ribbon chert, silicified burrows, disseminated chert, and massive chert that grades into limestone. Sources of chert are attributed to upwelling of deep bottom waters, silica-derived from freshwater mixing with saline water in deltaic complexes, and precipitation of silica through biological processes. Examination of fossiliferous rounded chert nodules, silicified burrows, ribbon chert, disseminat d chert, and stringers of chert, indicate that deposition was the result of secondary solution moving through areas with greater porosity. Disseminated chert, found in the Fossil Mountain Member, was deposited in the areas where the porosity was greatest. Massive chert in the Harrisburg Member formed at the water table where dissolution of the limestone occurred. This chert layer was then exposed to erosion. Chert emplacement occurred following the partial dolomitization of the limestone early in the diagenetic history. Some chert appears to have been deposited as secondary cement in the carbonate rock following cementation and dolomitization. Chert horizons in the upper part of the Kaibab Formation suggest that chert may have developed much later during an erosional cycle. This is suppo ted by colloform structures and gradation from a massive chert down to limestone. End_of_Article - Last_Page 525------------

Fossiliferous chert in South western Australia after the holocene transgression: a behavioural hypothesis

Fossiliferous chert in South western Australia after the holocene transgression: a behavioural hypothesis

Experimental studies in Precambrian paleontology: Structural and chemical changes in blue-green algae during simulated fossilization in synthetic chert

Experimental data concerning the effects of diagenesis and fossilization on soft-bodied microorganisms (particularly algae preserved in siliceous sediments) have been obtained through systematic monitoring of morphological and organic chemical changes in filamentous blue-green algae ( Lyngbya majuscula , Oscillatoriaceae) during simulated fossilization in synthetic chert. With increasing time and temperature, there were tendencies toward reddening, darkening, and fragmentation of algal filaments, reduction in the size of algal cells and sheaths, destruction of micellar order in sheaths (with consequent loss of bire-fringent character), coalescence of trichomes, and destruction of intracellular components with preferential preservation of sheaths and cell walls. In addition, some algal filaments were damaged by growth of quartz spherulites, producing artifactual morphologies that appear to have natural counterparts in Precambrian fossiliferous cherts. Original algal hydrocarbons, and particularly normal alkanes, were relatively stable, but several previously absent hydrocarbons were produced through decomposition of other organic compounds. Isoprenoid compounds, chlorins, and probably porphyrins were derived from the degradation of algal chlorophyll. The δC 13 PDB value of algal carbon was unaffected in most experiments but decreased by 3‰ under extreme time and temperature conditions. Results of this study suggest trends in the morphological degradation of naturally silicified algae, demonstrate that certain morphologies are artifacts of the silicification process, and suggest possible explanations of observed organic chemical trends in recent and ancient sediments.

Stratigraphy and Deformation of Paleozoic Section at Anaktuvuk Pass, Central Brooks Range, Alaska

The stratigraphic section at Anaktuvuk Pass consists of more than 13,000 feet of marine and non-marine sedimentary rocks ranging in age from Late Devonian through Permian. Non-marine Upper Devonian rocks include more than 6,300 feet of plant-bearing shale, siltstone, sandstone, and conglomerate, overlying a thick sequence of shale and slate. The Mississippian section, consisting of 4,680 feet of fossiliferous marine sandstone, black shale, dolostone, limestone, and chert, is overlain unconformably by approximately 400 feet of Permian marine shale and siltstone. Post-Paleozoic deformation of these rocks resulted in large-scale imbricate deep-seated thrust faults and large folds overturned toward the north; near the north front of the range the structures grade into broad o en folds associated with shallow thrusts that are limited to Mississippian and younger rocks. Most structural axes, both major and minor, trend east-west, and most thrusts, which tend to be localized along incompetent rock units, dip south, indicating northward release of deformational stresses. The Anaktuvuk thrust, exposed beneath isolated klippen on mountain summits northwest of Anaktuvuk Pass, is a major structural feature with minimum northward displacement of 8 miles. This thrust, confined to Mississippian and younger rocks, is shallow and appears to have moved northward from a structural high that forms the crest of the range. Absence of pre-Upper Devonian strata in exposed deep-seated thrust sheets suggests that the lowest unit of the Paleozoic section at Anaktuvuk Pass, thick in ompetent shale and slate, may constitute the base of a regional decollement in the northern half of the range. Within the area, intensity of deformation decreases gradationally northward as the Paleozoic section thins and as detrital sediments grade into coarser facies.

The erratics of the English Chalk

A description is given of the Th. Wiltshire and G.E. Dibley Collections of erratics from the Chalk comprising 388 stones. Most of the specimens are small, from ½ to 5 cm. in length, only twenty are more than 9 cm. in length. The rock types represented include quartzitic sandstone, quartzite, quartzschist, vein-quartz, chert, rhyolite, quartz-porphyry, granite, gneiss, tourmaline granite of luxulyan type, tourmalinised sandstone, phosphatic sandstone and limestone. The vein-quartzes are notable for strain and partial recrystallisation. The fossiliferous cherts have been examined by Dr. K.P. Oakley and Mr. C.D. Ovey who determine one as Carboniferous and others as probably Carboniferous. The few larger stones more than 9 cm. in length may have been transported in the roots of trees or attached to seaweed, but many, and perhaps the majority, of the others are considered to be gastroliths picked up from pebbly beaches by marine reptiles (? plesiosaurs) and dropped from their drifting carcases. The 150 stones found within a few feet of one another at Rochester are probably the gastroliths of one reptile. The erratics have been obtained from many and distant shores. The more specialised types among them indicate that the south-west of England and the Oslo Fjord-south-west Sweden region have contributed material.

Origin of Siliceous Dockum Conglomerates

A fossiliferous chert shingle discovered in a Dockum outlier in Motley County, Texas, contained fusulinids which apparently came from the Hueco, Franklin, or Glass mountains of West Texas. A suite of Dockum pebbles was collected from this outlier and a megascopic and microscopic examination indicated a source near the Marathon uplift, a distance of at least 300 miles.

Alluvial Fan of Potomac River

Research Article| September 30, 1931 Alluvial Fan of Potomac River1 MARIUS R. CAMPBELL MARIUS R. CAMPBELL Search for other works by this author on: GSW Google Scholar Author and Article Information MARIUS R. CAMPBELL Publisher: Geological Society of America Received: 01 Jun 1931 First Online: 02 Mar 2017 Online Issn: 1943-2674 Print Issn: 0016-7606 © 1931 Geological Society of America GSA Bulletin (1931) 42 (3): 825–852. https://doi.org/10.1130/GSAB-42-825 Article history Received: 01 Jun 1931 First Online: 02 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation MARIUS R. CAMPBELL; Alluvial Fan of Potomac River. GSA Bulletin 1931;; 42 (3): 825–852. doi: https://doi.org/10.1130/GSAB-42-825 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 General DescriptionWhen one travels southeastward from the Capitol at Washington he crosses Anacostia River and climbs a rather steep elevation known as Good Hope Hill. The western slope of this hill is composed of bedded deposits of Cretaceous and Tertiary ages, but the summit is capped by unconsolidated gravel and sand of a much younger formation. The gravel bed ranges in thickness from 20 to 40 feet and is composed largely of pebbles and cobbles of vein quartz, quartzite and fossiliferous chert; and the sand associated with the gravel is generally well washed and pure, although in some places it is intermixed with clay in the form of lenses and irregular masses. Good Hope Hill has an altitude of about 300 feet, but instead of being an isolated knob, as one might suppose from the name, it is a small part of a much dissected plateau capped by the . . . 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.