Brown Chert Research Articles

Microscopic imaging of human bloodstains: testing the potential of a confocal laser scanning microscope as an alternative to SEMs

The forensic interest on human bloodstains derives from their relation to crime investigation, whereas an archaeological and ethnographic concern arises from their occurrence because of warfare and ritual. The development of digital reflected light microscopes provided an opportunity to use ligh microscopy to study surface topographies in a more accurate way than previously. However, this enhancement has been focused on increasing magnification rather than resolution. An advanced type of light microscope is the confocal laser scanning microscope (CLSM). Its potential as an alternative to scanning electron microscopes (SEMs) for imaging human bloodstains was tested. A fragment of stone (brown chert) was smeared with human peripheral blood, air-dried, and stored indoors. After nearly two years, the sample was examined and imaged using an Olympus LEXT OLS4000 CLSM. The surface detail of CLSM images appeared to be comparatively lower than that of SEM micrographs of coated bloodstains taken at high-vacuum mode and high accelerating voltage, similar to that of SEM micrographs of uncoated bloodstains taken at low-vacuum mode and high accelerating voltage, and similar to or even higher than that of SEM micrographs of uncoated bloodstains taken at high-vacuum mode and low accelerating voltage. These results suggest that a CLSM is a practical alternative to SEMs for imaging human bloodstains when a very-high level of surface detail is not required.

Distribución de núcleos en el sector central de la mesta de Somuncurá (Río Negro, Argentina). Relaciones entre la base regional de recursos líticos y el aprovisionamiento de materias primas líticas

In this paper we address rock procurement among hunter-gatherers societies from Somuncura plateau through the study of cores and quarries. Different analyses allowed us to infer the possible trajectories of the main raw materials recognized in the Talagapa stream basin: chalcedony, brown chert and obsidian. The raw materials and cores distribution allowed us to distinguish different provisioning strategies, use patterns and cores discard. The use of the most frequently represented rocks is related to the trajectories. While chalcedony had a main role, brown chert acted as a complement in certain sectors in the basin and obsidian appears as a secondary raw material.

Thermal behaviour of organic radicals and paramagnetic centres in chert: A case study of Bergeracois brown chert, Dordogne, France

In order to successfully understand the complex evolution of prehistoric societies, archaeologists require absolute dating tools, which are not only accurate but also widely applicable. Thermoluminescence (TL) dating is one such approach that has been successfully used to establish a general chronological framework for prehistoric sites and is particularly suited for use on heated lithic artefacts. Experiments conducted in this study have clearly shown the applicability of Electron Spin Resonance (ESR) isothermal modelling in combination with TL dating to constrain firing temperature. This expands the potential application for TL dating to include artefacts treated at low firing temperatures. The present study shows potential in terms of precision and accuracy for framing the “equivalent firing temperature”. At the same time, the comparison of the TL signal with the lattice-defects and aluminium centres invigorate the use of ESR dating on heated flint, especially with samples that have received low thermal treatment. The presence of organic matter in large quantity raises concern on the pyrolysis effect on the luminescence signal; however, the use of ESR isothermal and isochronal modelling could potentially lead to the ability to overcome current interferences of the organic radicals within the dating signal of TL.

Tausonite and aluminum-fluorine titanite from the metamorphosed metalliferous sediments of the Triassic chert formation of the Sikhote Alin

Rare strontium mineral tausonite and a peculiar Al- and F-rich titanite variety were found in the metamorphosed metalliferous sediments of the Triassic chert formation of the Sikhote Alin, which are distinguished by the abundance of native elements, intermetallic compounds, and metal solid solutions, as well as the presence of diverse Au, Ag, and PGE minerals. Tausonite was documented in the manganese (metamorphosed siliceous-rhodochrosite) rocks of the Ol’ga mining district and in the “brown cherts” (siliceous rocks with manganese garnet and spessartine) of the Dal’nerechensk district, Primorye. It forms rather numerous grains 2–10 μm across usually occurring as inclusions in quartz or rhodonite. According to the electron microprobe analysis, in addition to Sr, Ti, and O, the mineral contains only Fe3+ (up to 0.20 a.f.u.). Aluminum-fluorine titanite was found in the “brown cherts” of the Dal’nerechensk district of Primorye (upper reaches of the Gornaya River). Its crystals are up to 200 × 200 μm in size. The recalculation of the microprobe analyses to crystal chemical formulas indicated that up to half of the Ti sites in the structure of this mineral may be occupied by Al. The decrease of the total positive charge owing to the Al3+ substitution for tetravalent Ti4+ is compensated for by a decrease in the total negative charge owing to F− substitution for O2− via the scheme Al3+F− → Ti4+O2−. The occurrence of considerable amounts of F substituting for oxygen in the titanite structure and, as a consequence (owing to the crystal chemical features of the mineral), the high Al content were related to the reduced character of the metamorphism of the metalliferous deposits.

Primor’ye as a new promising region of Russia with gold-palladium-platinum ore mineralization of a nontraditional type

The following regionally distributed contact-metamorphosed metalliferous sediments occur in association with each other in the lower part (Upper Olenekian‐Ladinian) of the Triassic siliceous formation of the Sikhote-Alin, which is enriched in carbon: manganese‐silicate (metamorphosed siliceous‐rhodochrosite) rocks, “brown cherts” (cherts with pyrophanite and spessartine), tin‐iron ores, “ilmenite‐biotite‐feld spar” (metamorphosed argillous) rocks, and “itabirites” (gold-bearing jaspers). These rocks occur in association with the products of hydrothermal regeneration composing bodies of different morphology and composition, including deposits of manganiferous skarnlike (amphibole‐pyroxene) rocks and skarns [1‐3]. Metalliferous sediments and products of their regeneration contain nickel and cobalt sulfides, arsenides, antimonides, tellurides, sulfoarsenids, sulfoantimonides and sulfotellurides, minerals of rare earth elements, thorium, uranium, barium, vanadium, and other minerals. Furthermore, reduced forms of different metals are common: native elements, solid solutions, intermetallic compounds, phosphides, and silicides. Associations of the reduced forms occur in pores and microsize fissures with organic matter. They were formed during the contact-metamorphic process under high temperatures (according to the admixture concentration level of several elements in native metals) accompanied by hydrocarbon decay and hydrogen reducing of oxidized forms. In view of the degree of the metalliferous rock distribution and the usual presence in it of minerals of Au, Ag, Pt, and Pd (a separate publication devoted to these minerals has been prepared [5]), the question of the concentration level of noble metals in these rocks becomes very important. Analyses performed earlier [1, 3] could not give an unambiguous answer to this question. Although they revealed high concentrations of Au, Pt, and Pd in separate samples, they characterized only manganese‐silicate rocks, their amount was insufficient, and reproducibility was weak. The concentrations of Au and Pt were found to be lower (one order of magnitude or more) than was expected according to the results of the investigation of mineral forms and dissolution of samples in hydrofluoric acid. The following three analytical methods have been used in the present work: fire assay with atomic absorption (AA) finishing, ICP-MS, and AA. The results of the fire assay analysis were found to contradict the data from the microprobe investigation and dissolution of samples in hydrofluoric acid. As was established during the microprobe investigation of the cinder, the losses were connected with

Gold and platinum group metals in skarns of the Ol’ginsk and Dal’negorsk ore districts of Primorye and some issues of metallogeny of the southern Sikhote Alin region

The Triassic‐Jurassic carbonaceous sequence of Sikhote Alin includes metalliferous sediments represented by siliceous‐rhodochrosite rocks and their metamorphosed analogues [3, 4], siliceous rocks with pyrophanite (“brown cherts”), tin‐iron ores, “ilmenite‐ biotite‐feldspar” (metamorphosed clayey) rocks, and “itabirites.” They are characterized by high contents of Au, Ag, Pt, and Pd [2] and the ubiquitous presence of minerals of these elements. Hydrothermally altered sandstones, as well as siliceous‐clayey and siliceous rocks, which are associated with syngenetic metalliferous rocks, contain grains of gold, silver, argentite, platinum, Pd-platinum, itenbohaardite, and other minerals of noble metals. It should be mentioned that identifications of all minerals mentioned in this paper have been confirmed by microprobe analyses. Another type of hydrothermal ores is represented by Mn-rich amphibole‐pyroxene rocks that contain native gold, silver, Pdplatinum, and other minerals of gold, silver, and platinum group metals (PGM). Hydrothermal ores are products of the regeneration of metalliferous rocks due to the evolution of Late Cretaceous granitoid massifs. The amphibole‐pyroxene rocks formed after calcareous sandstones, which are probably of Late Triassic age [3]. The southern Sikhote Alin region incorporates numerous Late Cretaceous skarn and vein (cavity-filling) deposits of lead, zinc, silver, tin, tungsten, and iron. Skarns are characterized by high concentrations of Mn derived from manganese rocks [1]. Similarly as other metalliferous rocks, the manganese rocks are enriched in Pb, Zn, Ag, Sn, W, and Fe. Hydrothermal deposits of these metals define the metallogenic profile of the southern Sikhote Alin region. Manganese and other metals mentioned above were probably derived from metalliferous rocks of the Triassic‐Jurassic carbonaceous sequence. The metalliferous rocks and associated hydrothermal rocks contain Au and PGM. For example, these metals are concentrated in amphibole‐pyroxene rocks of the Shirokaya Pad area of the Ol’ginsk district. These rocks are analogues of the adjacent manganiferous

Metalliferous sediments of the Triassic cherty formation in the Ol’ga ore district of primorye: Tin-noble metal ores of a new genetic type

The Triassic cherty formation of Sikhote Alin [1] hosts metalliferous deposits. They are commonly represented by siliceous‐rhodochrosite rocks and their metamorphosed analogues (primarily, consisting of Mn-silicates and aluminosilicates) with high concentrations of Ga, Au, Pt, Pd, and other metals [3]. In the Ol’ga district, the metalliferous deposits are also represented by chocolate-brown siliceous rocks (hereafter, brown cherts) and tin‐iron ores. The metalliferous deposits occur in the Middle‐ Late Triassic siliceous‐clayey sequence. They make up at least one ore-bearing unit (thickness of 5 m or more) represented by brown cherts with a manganese rock bed near the upper contact. The overlying tin‐iron ore bed varies from tens of centimeters to a few meters in thickness. Judging from locations of native exposures, talus, and alluvial fragments, the ore-bearing unit is developed over an area of no less than 20 km 2 (Fig. 1). The manganese rocks are composed of rhodonite, pyroxmangite, and spessartine with a maximum V 2 O 3 content of 0.20 wt % [2, 4]. The rocks contain kanoite, tephroite, manganactinolite, dannemorite, tirodite, pyrosmalite, pyrophanite, hubnerite, scheelite, native silver, native gold, minerals of the cobaltite‐ gersdorffite series, pentlandite, millerite, violarite, tetradymite, tellurobismuthite, and other minerals. The manganese rocks also include Au (up to 35 g/t), Pt (0.08‐ 0.33 g/t), Zn (up to 5.97 wt %), Cu (up to 0.64 wt %), Ni (up to 0.14 wt %), and Co (up to 0.10 wt %) [3]. Nearly all polished samples contain native silver dissemination up to 20 µ m in diameter. Gold grains ( n mm in size) extracted by the acid treatment of manganese rocks are characterized by a high grade of fineness

Aurignacian Settlement Patterns in the Vézère Valley

Etude de la mobilite des groupes aurignaciens du bassin de la Vezere a partir de l'economie de la matiere premiere lithique et de la saisonnalite animale. Ces elements fournissent des donnees nouvelles sur l'extension du territoire exploite, sur le degre de sedentarisation et de saisonnalite humaine

Aurignacian Settlement Patterns in the Vézère Valley

Aurignacian Settlement Patterns in the Vézère Valley

Composition and origin of hydrothermal ironstones from central Pacific seamounts

Ironstones recovered from five Late Cretaceous seamounts in the central Pacific region probably formed during late-stage edifice-building volcanism. Ironstones are dense and compact with the appearance of brown chert. The ironstones are characterized by a goethite mineralogy with FeOOH contents up to 88%, extreme fractionation of Fe and Mn, low trace-element and rare earth element abundances, low Co Zn ratios, and isotopic equilibration temperatures of about 20–45 °C. These characteristics indicate that the ironstones formed from hydrothermal fluids. Ironstones probably formed below the seawater-seafloor interface, as indicated by their occurrence as a proximal hydrothermal deposit, presence of primary goethite cement, pervasive replacement of rocks by goethite, and absence of interbedded pyro-clastic beds.

Permian Stratigraphy at Carlin Canyon, Nevada

Three new formation names are defined for a hitherto undescribed section of Permian marine sedimentary rocks exposed north of Carlin Canyon, Elko County, northeastern Nevada. The name of Buckskin Mountain formation is proposed for a 1,200-foot uniform sequence of yellow-tan quartzose calcisiltites and minor gray calcarenite beds of Wolfcampian age conformably overlying the Pennsylvanian-Permian Strathearn formation and conformably overlain by the Permian Beacon Flat formation. The name of Beacon Flat formation is proposed for a three-member unit 2,800 feet thick. The 550-foot lower member of gray, silty calcarenites and chert beds contains the Wolfcampian-Leonardian boundary. Alluvium covers the undescribed middle member. Cherty, fossiliferous, gray calcarenites make up the 1,150-foot-thick upper member, conformably overlain by the Permian Carlin Canyon formation. The name of Carlin Canyon formation is proposed for a 1,225-foot sequence of tan quartzose calcisiltites and massive brown cherts of Leonardian and possibly Guadalupian age, unconformably overlain by the Miocene-Pliocene Humboldt formation. The Buckskin Mountain formation is probably correlative with parts of the Carbon Ridge and Arcturus formations. Carlin Canyon formation sediments reflect orogeny and volcanism taking place in western Nevada, as well as local uplift, during Leonardian and possibly Guadalupian time.

Stratigraphy of La Honda and San Gregorio Quadrangles: ABSTRACT

The oldest rocks exposed are Upper Cretaceous foraminiferal mudstones, graded sandstones, and conglomerates (9,500 feet) occurring in a fault slice along the coast south of Pescadero. Not in contact is the Butano formation (5,000 feet) of Eocene age, consisting of interbedded sandstones, siltstones, and mudstones. The sandstones are thicker and cleaner in the upper part of the Butano formation and produce oil in the La Honda field. Conformably overlying the Butano formation are 2,500 feet of San Lorenzo mudstones and siltstones (upper Eocene A-1 zone to lower Zemorrian) which are cut by diabase sills and dikes. These dikes were feeders to basalt flows which poured from subaerial volcanoes into shallow water. The volcanic rocks are interbedded with upper Zemorrian and Sauc sian mudstones, quartzose sandstones, and organic calcarenites. This sequence totals 2,000 feet in thickness and is overlain by 500 feet of brown chert and laminated mudstone (Relizian ?). Transgressing all older rocks are the upper Miocene cherts and diatomaceous mudstones (0-9,000 feet thick) of the Monterey formation. The Pliocene Purisima formation (5,650 feet) overlies the Monterey comformably and is still transgressive. It is characterized by the first influx of andesitic debris, probably from the Sierra Nevada. The Purisima is divided into five mappable members, which from the base upward are: tuffaceous siltstone and sandstone member containing small amounts of oil in the La Honda field (2,150 feet); siliceous mudstone member (2,300 feet); pebbly sandstone member (150-350 feet); udstone member (450 feet); fine sandstone member (400 feet). Pleistocene terraces, recent alluvium, and landslides complete the stratigraphic column. It is believed that the Butano, the lower Miocene volcanics and the Purisima formation can be directly correlated across the present San Andreas fault into the Stanford-Woodside area. The correlation suggests that lateral displacements along the fault in this area may be a mile or two, but not hundreds of miles. End_of_Article - Last_Page 257------------

The Gravels at Reculver, Kent

In January, 1912, Mr. Reginald Smith read a paper before the Society of Antiquaries entitled “Flint Implements of Special Interest,” in which figured an implement of the Thames pick type— the author relegating it to the palæolithic period. I will read an extract from this paper describing the “pick.”“The implement in question was found during the War by the late Captain Harvey Webb while searching the coastal gravel near Netley Hospital. It is a flint rod of roughly triangular section, with one face chipped flat; one end is nosed with bold fluting, the other is crusted and therefore, not functional. The whole is patinated an ochreus colour and the ridges are much battered by rolling.Length 6 inches—the flat face 2 inches across. It was submitted to the British Museum in November, 1916, with other (obviously palæolithic) specimens from the same deposits: a large pear-shaped hand-axe with brown patina; a white St. Acheul ovate much rolled; a cordate brown St. Acheul implement; unrolled; a pointed triangular hand-axe; and a brown chert ovate, this last being from the top of the loam beneath the gravel.”