Geologic sources and geographic distribution of sand tempers in prehistoric potsherds from the Mariana Islands

Temper sands in prehistoric potsherds of the Mariana Islands include terrigenous detritus derived from Paleogene volcanic bedrock and calcareous grains derived chiefly from modern fringing reefs, but also in part from uplifted Neogene limestones overlying volcanic bedrock. Calcareous sands are nondiagnostic of island of origin, but volcanic sands and the terrigenous component of hybrid sands composed of mixed terrigenous and calcareous grain types can be traced to geologic sources on Saipan and Guam, the only occupied islands where volcanic bedrock is extensively exposed. Quartzose tempers of several types were derived exclusively from dacitic volcanic rocks on Saipan. Nonquartzose tempers of andesitic parentage derive from both Saipan and Guam, but abundance of orthopyroxene as well as clinopyroxene is diagnostic of Saipan andesitic tempers, the presence of olivine is diagnostic of selected tempers from Guam, and placer temper sands rich in heavy ferromagnesian minerals occur only in sherds on Guam. Temper analysis documents widespread ceramic transfer from Saipan to other islands throughout Mariana prehistory, and more restricted ceramic transfer from Guam to nearby Rota, although the origin of some andesitic temper types is petrographically indeterminate. © 2001 John Wiley & Sons, Inc.     

Petrography and provenance of Laecanius Amphorae from Istria,northern Adriatic region,Croatia

Amphorae sherds from the Laecanius workshop of Roman Istria (10–5 B.C. and 78 A.D.), Croatia, were studied by integrating archaeological and geological techniques including fabric analysis, thin‐section petrography, X‐ray diffractometry (XRD), and heavy mineral analysis. The fabric of the sherds showed distinctive characteristics, permitting their classification and allocation into nine fabric groupss. Petrography revealed that quartz is the dominant clastic component, whereas carbonate is common as temper; XRD provided information on firing temperatures that ranged between 750 and 900°C. The sherds contain diverse heavy mineral suites with generally high epidote and garnet proportions; zircon is occasionally important. Garnet/epidote ratios and the presence of diagnostic species (pyroxene, hornblende) showed systematic variations that coincided with similar variations in fabric characteristics. Heavy mineral signatures of amphorae produced in other workshops proved essential in differentiating them from Laecanius sherds. A comparative heavy mineral analysis of terra rossa samples from the vicinity of the workshop indicated that terra rossa was the major source for the paste. Differences observed in the heavy mineral composition of the sherds and terra rossa were interpreted by the spatial heterogeneity of the latter and the mixing of the paste with sandy temper. Fresh Adriatic sponge spicules in the majority of Laecanius sherds and the temper‐derived, generally immature heavy mineral assemblages suggest that sandy deposits from the Adriatic were used for the clastic temper. © 2006 Wiley Periodicals, Inc.     

Sources of sand tempers in prehistoric Tongan pottery

The sources of volcanic temper sands in prehistoric pottery found on low-lying raised-coral islands of Tonga have long been uncertain. The paucity of noncalcareous sand on most inhabited Tongan islands has led to the suggestion that temper was imported from the active magmatic are to the west, or even that most pottery was imported to Tonga from Fiji. The simple mineralogy of the tempers, which are composed almost exclusively of pyroxene and plagioclase mineral grains, volcanic rock fragments, and opaque ferro-magnesian oxide grains, is compatible with derivation from Tongan volcanics, but island volcanoes of Tonga lack deposits of rounded and well-sorted sands that are similar texturally to the tempers. Discovery of local placer deposits composed of volcanic sand on beaches otherwise composed of calcareous reef detritus within the Ha'apai Group of central Tonga provides a satisfactory local source for temper on the shorelines of several inhabited islands. The beach placer sands were apparently derived from reworking of thick tephra deposits that mantle the islands. Detailed compositional analysis of temper sands in numerous ancient Lapitoid potsherds from all the constituent island groups of Tonga implies that pottery making was once a widespread industry making use of locally available raw materials. Stylistically diagnostic protohistoric Fijian potsherds, found in small numbers on several islands in Tonga, can be distinguished from the older indigenous Lapitoid wares by their anomalous tempers, which contrast sharply with the Tongan volcanic temper sands. © 1996 John Wiley & Sons, Inc.     

Oceanic tectonic islands

The origin of oceanic islands has been the subject of much speculation, starting with Darwin almost two centuries ago. Two classes of oceanic islands can be identified: ‘volcanic islands’, which form due to excess volcanism caused by melting anomalies in the suboceanic mantle, and ‘tectonic islands’, which form due to transpressive and/or transtensional tectonics of blocks of oceanic lithosphere along transform faults. Modern and sunken tectonic islands from the Atlantic Ocean and Indian Ocean and the Caribbean Sea and Red Sea expose mantle and lower‐crust lithologies and display an elongated narrow morphology; in contrast, volcanic islands expose basalts and have near‐circular morphology. Both are often capped by carbonate platforms. The life cycle of tectonic islands tends to be more complex than that of most volcanic islands; their elongated narrow morphology, together with their tectonic instability and high seismicity, affect the architecture of the carbonate platforms capping them, limiting coral reef development and favouring rhodalgal–foramol biota associations.     

Petrography and geologic provenance of sand tempers in prehistoric potsherds from Fiji and Vanuatu,South Pacific

Indigenous sand tempers in prehistoric potsherds from Fiji, Vanuatu, and neighboring islands of the eastern Solomon outliers and northern Melanesian borderland have diverse compositions reflecting the varied geology of different islands in patterns controlled by regional geotectonic relations. Mineralogical compositions of noncalcareous temper sands reflect the nature of the bedrock sources on different islands. Temper analysis indicates that the ceramic assemblages recovered from most archaeological sites within the region were made locally or nearby, but also documents interisland ceramic transfer in widely varying volumes over distances as much as several hundred kilometers. Contrasts in island geology allow exotic wares to be identified without ambiguity but to varying degrees of specificity in terms of islands of origin. Rare sherds of New Caledonian wares have been collected in prehistoric context from several islands in Vanuatu, but there is as yet no temper evidence for prehistoric ceramic transfer between Vanuatu and Fiji. © 2001 John Wiley & Sons, Inc.     

Evidence for a single clay/temper source for the manufacture of Middle and Late Helladic Aeginetan pottery from Asine,Greece

In an effort to further characterize the Middle and Late Helladic pottery industry on Aegina, we have analyzed amphibole in 23 sherds imported to the coastal settlement of Asine. The sherds derive from vessels of different classes and shapes and range in age from MH I‐II to LH IIIB‐IIIC Early. All sherds come from vessels that carry manufacturing marks, and their amphiboles have compositions that are incompatible with those of Methana, Poros, and Melos. Twenty of the sherds have amphiboles that are identical in composition and overlap a narrow range of amphibole compositions found in specific lava flows on the northern portion of Aegina. Given that the dacites across Aegina contain amphiboles with a wide range in compositions, we suggest that the narrow range of amphibole compositions in the sherds indicates that they were derived from either a specific clay source on the island, located in a stream system southeast of the prehistoric settlement at Kolonna, or that the potters used a specific temper source along the same stream system. Multiple clay or temper sources would have produced sherds with a broader range of amphibole compositions reflecting the diversity of amphibole compositions found on Aegina. One sherd has amphibole compositions indicative of an additional Aeginetan component that is not found in the other sherds. Two sherds have amphiboles with compositions that do not match any known reference amphiboles for Aegina, Methana, Poros, or Melos. These may have been derived from still unsampled dacites on Aegina or have been manufactured from materials located outside the Saronic Gulf. © 2004 Wiley Periodicals, Inc.     

Sources of sandstone artifacts and pottery from Lost Dune,a late prehistoric site in Harney County,southeastern Oregon,U.S.A.

Granitic constituents suggest distant plutonic sources for sherds representing four of six low‐fired brown ware pots and for eight of ten sandstone artifacts from Lost Dune (35HA792), a Late Prehistoric bison processing camp in Harney Basin of southeastern Oregon, a Tertiary volcanic and sedimentary region. Eight sandstone artifacts match granite‐derived sandstone near Oregon's Owyhee River, and three former pots match altered granite and rhyolite in Idaho's Owyhee Mountains. A fourth corresponds to mixed hydrovolcanic basalts near the sandstone abrader source. The sources delineate a 30 × 70 km area > 100 km from Lost Dune. Two other pots and two milling stones match deposits near this area and elsewhere. The determined sources suggest people who used Shoshoni pots and knives at Lost Dune resided in southeastern Oregon. Pots with temper from elevations above 1500 m or recovered as sherds above 1500 m might be made in summer root‐digging camps. © 2002 Wiley Periodicals, Inc.     

The reliability of thermoluminescence dating: A pilot experiment

The accuracy of thermoluminescence dating of pottery was tested by utilizing dendro-chronologically dated provenances in the northern part of the American Southwest. Fairly accurate determinations were achieved for potsherds recovered from sedimentary rock soil, while much younger dates were obtained for potsherds recovered from volcanic rock soil. The reduction of accumulated dose through radon escape might be responsible for the much younger dates of the sherds buried in volcanic soil. The application of the technique to samples recovered from soil matrices in volcanic materials, to burnt volcanic rocks, or to sherds containing ample volcanic rocks should be avoided for reliable determinations.     

A Middle Miocene carbonate embankment on an active volcanic slope: Ilhéu de Baixo,Madeira Archipelago,Eastern Atlantic

Carbonate factories on insular oceanic islands in active volcanic settings are poorly explored. This case study illuminates marginal limestone deposits on a steep volcanic flank and their recurring interruption by deposits linked to volcaniclastic processes. Historically known as Ilhéu da Cal (Lime Island), Ilhéu de Baixo was separated from Porto Santo, in the Madeira Archipelago, during the course of the Quaternary. Here, extensive mines were tunnelled in the Miocene carbonate strata for the production of slaked lime. Approximately 10 000 m³ of calcarenite (−1 to 1ø) was removed by hand labour from the Blandy Brothers mine at the south end of the islet. Investigations of two stratigraphic sections at opposite ends of the mine reveal that the quarried material represents an incipient carbonate ramp developed from east to west and embanked against the flank of a volcanic island. A petrographic analysis of limestones from the mine shows that coralline red algae from crushed rhodoliths account for 51% of all identifiable bioclasts. This material was transported shoreward and deposited on the ramp between normal wave base and storm wave base at moderate depths. The mine's roof rocks are formed by Surtseyan deposits from a subsequent volcanic eruption. Volcaniclastic density flows also are a prevalent factor interrupting renewed carbonate deposition. These flows arrived downslope from the north and gradually steepened the debris apron westwards. Slope instability is further shown by a coral rudstone density flow that followed from growth of a coral reef dominated by Pocillopora madreporacea (Lamarck), partial reef collapse, and transport from a more easterly direction into a fore‐reef setting. The uppermost facies represents a soft bottom at moderate depths in a quiet, but shore‐proximal setting. Application of this study to a broader understanding of the relationship between carbonate and volcaniclastic deposition on oceanic islands emphasizes the susceptibility of carbonates to dilution and complete removal by density flows of various kinds, in contrast to the potential for preservation beneath less‐disruptive Surtseyan deposits. Copyright © 2013 John Wiley & Sons, Ltd.     

北大巴山志留系滔河口组火山碎屑岩相序、组构特征及古火山作用环境分析

志留系滔河口组是一套发育于北大巴山地区的火山岩-火山碎屑岩-沉积岩组合。在1:10000地质填图和大比例地质剖面实测基础上,通过详细的火山碎屑岩相序和组构分析,本文在滔河口组火山-地层中共识别和划分出22个岩相,5个相组合类型。区域岩相测量与对比揭示,滔河口组火山-沉积宏观序列自下而上由玄武岩相(一般下部为块状粗粒/细粒玄武岩相、上部为枕状玄武岩相)、凝灰角砾岩相、再沉积富辉石火山碎屑砾岩相、无结构或叠瓦状凝灰质粗砾岩相、凝灰质砂岩相、生物灰岩相或泥岩相构成。岩相组合横向变化显示滔河口组古火山活动西强东弱,火山活动类型为斯托柏林型(Strombolian-type eruption)喷发。相对地,研究区西部火山-沉积序列发育较为完整。滔河口组的地层序列与岩石组合与板内火山活动产物相似,本文认为北大巴山地区志留系滔河口组火山岩-火山碎屑岩-沉积岩组合形成于洋岛或海山构造环境,是板内拉伸作用的产物。     

Provenance of sand temper in Hohokam Ceramics,Arizona

Sand temper compositions of regionally distinct Hohokam pottery sherds were determined by detailed point counts using sedimentary petrographic methods. Different temper compositions from different sites were compared with maps of sand composition zones within the geographic range of the pottery in order to establish the probable provenance of each sherd. A number of probable instances of intraregional pottery exchange were identified. The larger number of sand sources in undecorated vs. decorated pottery at each site suggests that undecorated pottery was made in more places than decorated vessels, and may have been traded differently as well. Petrographic analysis of temper is a useful method for studying exchange of homogeneous pottery in geologically diverse areas, and for investigating prehistoric Hohokam interaction in the Tucson and Red Rock Basins on a scale not possible with traditional archaeological techniques.     

Facies architecture and cyclicity in a mosaic carbonate platform: effects of fault-block tectonics (Lower Lias, Causses platform, south-east France)

In the Causses platform (south‐east France), Late Hettangian to Sinemurian deposits were interpreted previously as shallow‐water carbonate ramp deposits. A new look at these deposits has shown a fault‐controlled mosaic carbonate platform that is different from the carbonate ramp models. Within the platform mosaic, 15 lithofacies have been recognized, which are organized in four facies associations, including peritidal, restricted shallow sub‐tidal, sand dunes and sub‐tidal shelf facies associations. The rapid lateral and vertical facies changes, and the lack of consistent landward or seaward direction indicated by the pattern of facies changes, question the existence of a shoreline suggested by the traditional models for this region. Instead, the facies organization and cycle stacking pattern suggest deposition in a mosaic of intertidal islands between which sub‐tidal restricted or open conditions could coexist in very close proximity. Such a platform mosaic would have been defined by tectonic activities along normal faults which segmented the shallow‐water Causses platform. The facies and facies associations are arranged into metre‐scale, peritidal and sub‐tidal cycles that are also variable. Certain cycles show the same stacking pattern in all the sections and seem to be traceable over tens of kilometres. On the contrary, other cycles cannot be correlated; they are present only in specific sections and have a maximum lateral extension of 1 or 2 km. These metre‐scale cycles stack to form four medium‐scale cycles bounded by surfaces that display sub‐aerial exposure features. Medium‐scale cycles stack into two larger‐scale cycles (tens of metres thick) and are bounded by well‐defined karstic surfaces. Based on their lateral continuity and their stacking pattern, the metre‐scale cycles are controlled probably by high frequency eustatic variations overprinting the topographic irregularities formed by differential subsidence of fault‐bounded blocks. Episodic fault activities may reorganize the topography so that, even if eustatic changes may still be the major control of cycles, the expression and number of cycles could be different. Cycles of medium and large‐scale are interpreted as being allogenic, controlled by changes in eustasy and/or subsidence rates as evidenced by their lateral continuity and the correlations of the large‐scale cycles with third‐order depositional sequences.     

Rapid bathymetric surveys in marine volcanic areas: A case study in panarea area

The Differential Global Positioning System technique (DGPS) and an echo-sounding gear, both managed by a portable computer, were used on a small boat with the aim to perform rapid bathymetric surveys in shallow water in the still active volcanic area of the Panarea island. Preplanned routes were driven by a real time navigation software that allowed to perform several sections of the sea floor across the caldera in short time and high accuracy. Planar coordinates and depths were obtained with average accuracies of ±30cm and ±10cm respectively. Finally a Marine Digital Elevation Model (MDTM) was produced which allowed a detailed picture of the seafloor and showed the spatial distribution of the active gas ventings of this submarine volcanic area, located in the volcanic arc of the Aeolian islands (Southern Italy).     

四川义敦地区上三叠统曲嘎寺组岩相古地理研究

对四川义敦地区上三叠统曲嘎寺组9幅1：5万区调图幅和44条剖面和沉积等厚线的综合分析研究,认为该区曲嘎寺组主体部分发育了浅海陆棚-泻湖相、开阔碳酸盐台地相、扇三角洲与碳酸盐台地交互相、浅海陆棚相、局限台地相等5种相组合,并可划分为义敦弧后前陆盆地、义敦火山弧及弧内火山洼地、沙鲁里边缘海等3个次级火山-沉积盆地,在义敦初始火山弧内发育有果德火山穹隆、根隆火山穹隆、扎翁拉火山洼地等更次一级的古地貌单元。     

Late Carboniferous to early Permian sedimentaryetectonic evolution of the north of Alxa,Inner Mongolia,China: Evidence from the Amushan Formation

The late Paleozoic evolution of the Wulijishanhen(WSH)-Shangdan(SD) area near to the Chaganchulu Ophiolite belt is reinterpreted. Analysis of the upper Carboniferous to lower Permian sedimentary sequence, biological associations, detrital materials, sandstone geochemistry and volcanic rocks indicates that the SD area was an epicontinental sea and rift during the late Paleozoic rather than a large-scale ocean undergoing spreading and closure. This study reveals that the actual evolution of the study area is from the late Carboniferous to the early Permian. The fusulinids Triticites sp. and Pseudoschwagerina sp.in the limestones demonstrate that the Amushan Formation develops during the late Carboniferous to the early Permian. The limestones at the base of the SD section indicate that it is a stable carbonate platform environment, the volcanic rocks in the middle of the sequence support a rift tectonic background, and the overlying conglomerates and sandstones are characteristic of an epicontinental sea or marine molasse setting. The rift volcanism made the differences in the fossil content of the SD and WSH sections and led to two sections expose different levels within the Amushan Formation and different process of tectonic evolution. Moreover, the geochemical characteristics and detrital materials of the sandstones show that the provenance and formation of the sandstones were related to the setting of active continental margin. The quartz-feldspar-lithic fragments distribution diagram indicates that the material source for the sandstones was a recycled orogenic belt. Thus, the source area of the sandstones may have been an active continental margin before the late Carboniferouseearly Permian. The characteristics of the regional tectonic evolution of the area indicate that the region may form a small part of the Gobie Tianshan rift of southern Mongolia.     

东天山大南湖岛弧带石炭纪岩石地层与构造演化

详细的地质解剖工作表明,东天山地区大南湖岛弧带石炭纪出露4套岩石地层组合,即早石炭世小热泉子组火山岩、晚石炭世底坎儿组碎屑岩和碳酸盐岩、晚石炭世企鹅山组火山岩、晚石炭世脐山组碎屑岩夹碳酸盐岩。根据其岩石组合、岩石地球化学、生物化石、同位素资料以及彼此的产出关系,认为这4套岩石地层组合的沉积环境分别为岛弧、残余海盆、岛弧和弧后盆地。结合区域资料重塑了大南湖岛弧带晚古生代的构造格架及演化模式。早、晚石炭世的4套岩石地层组合并置体现了东天山的复杂增生过程。     

Early Cenozoic volcanism of the Kolyuchin-Mechigmen graben, Chukotka Peninsula

The paper reports new isotope-geochemical data on Late Paleocene-Early Eocene basalts from the central part of the Kolyuchin-Mechigmen graben, eastern Chukotka Peninsula. The distribution of the major and trace elements and trace-element ratios indicates that the basalts were formed in a marginal-continental rift setting. The peculiar feature of the basalts is a combination of depleted within-plate and suprasubduction geochemical signatures, which make the volcanic rocks from Mt. Otdel’naya different from rocks of suprasubduction volcanic belts and from tholeiites and alkaline lavas of continental rifts and oceanic islands. Extremely high ⁸⁷Sr/⁸⁶Sr ratios in the studied basalts as compared to those of similar volcanic rocks from extension zones are probably related to the involvement of carbonate material in the magma generation zone.     

Microstructures of phosphatic porcelain from sintering to vitrification: Evidence from sherds excavated in Charleston,South Carolina

Eight phosphatic porcelain sherds recovered from various historical sites in Charleston were analyzed by electron microprobe. Some sherds contain sulfur (2.3–3.1wt.% SO₃); others contain only traces of this component. The analytical data suggest that the sulfurous sherds are Bow porcelain (London, Bowcock period, ca. 1755–1769). The origin(s) of the low‐S samples remains unidentified; one compositionally resembles “gold‐anchor period” (phosphatic) Chelsea porcelain (London, ca. 1756–1769) but its decoration is inconsistent with known wares produced by this factory during that era. The degree of vitrification is highly variable, particularly among the SO₃‐poor samples. The melt phase is strongly enriched in incompatible elements (Ti, Fe, Na, K). The phosphate phase [calcined bone ash (hydroxyapatite)] in poorly vitrified samples hosts minute melt blebs, but remains porous. With increasing vitrification, these melt blebs increase in size and begin to coalesce, ultimately forming ameboid patches up to ∼10 μm in diameter. In the most vitrified samples, the coalesced melt “leaks” into the matrix, leaving behind a phosphate phase that lacks pores and melt and has a lower CaO/P₂O₅ ratio (=2.7, molecular proportions) than either hydroxyapatite (3.3) or β‐whitlockite (3.0). The two varieties of phosphate occur in some poorly vitrified samples, suggesting the recycling of high‐fired wasters (as “grog”) in their ceramic pastes. Melt compositions vary with contiguous mineralogy, accounting for their divergence from the ternary eutectic in the Ca₃(PO₄)₂‐CaAl₂Si₂O₈‐SiO₂ system. The resorption of phosphate by the matrix melt virtually precludes recognition of anorthite formed by the “non‐phosphate glass equation.” © 2011 Wiley Periodicals, Inc.     

The minor and trace element geochemistry of volcanic rocks from Truk,Ponape and Kusaie,Eastern Caroline Islands; the evolution of a young hot spot trace across Old Pacific Ocean Crust

Recent paleomagnetic and K-Ar age dating studies in the Caroline Islands show that the high volcanic islands of Truk, Panape and Kusaie formed at the same shallow latitude and display a progression of ages increasing westward from 1 m.y. (Kusaie), through 6 m.y. (Ponape) to 12 m.y. (Truk). These data suggest that the islands were formed by a young hotspot or melting anomaly. One hundred and fifty volcanic rocks from these three islands have been analysed for major and 15 trace elements and results indicate that shield-building lavas on each island (1) evolved by low-pressure open-system fractional crystallisation of a small range of partial melts and (2) became more alkaline with time from Truk to Kusaie. The secular geochemical variation along the Caroline chain may represent a hotspot trace whose magma production was slowly declining over the past 14 m.y.