Stratigraphic Data Research Articles

Tectonic–sedimentary interplay of a confined deepwater system in a foreland basin setting: the Pennsylvanian lower Atoka Formation, Ouachita Mountains, U.S.A.

ABSTRACT Submarine fans deposited in structurally complex settings record important information on basin evolution and tectonic–sedimentary relationships but are often poorly preserved in outcrops due to syndepositional and post depositional deformation. This study aims to understand the influence of tectonics on the deposition of the synorogenic Pennsylvanian lower Atoka submarine fan system deposited in a structurally complex foreland basin during the Ouachita orogeny. This study is a synthesis of new outcrop stratigraphic data as well as published stratigraphic and structural data. The lower Atoka crops out in the Ouachita Mountains and the southern Arkoma Basin and is divided into three structural–depositional zones: the foredeep, the wedge top, and the continental foreland. The mean paleoflow is axial, and each zone exhibits unique patterns in facies distribution. The foredeep consists of two fan systems, a large westward-prograding fan that exhibits significant longitudinal and lateral facies changes, and a small eastward-prograding fan on the western part. The wedge top consists of a westward-prograding fan that exhibits subtle longitudinal facies change. The continental foreland consists of small slope fan systems along the northern and western margins. By comparing to basin morphology and structural styles, we interpret the facies distribution patterns in the three zones as the result of different combinations of lateral structural confinement, axial and lateral sediment supply, and paleogeography. This study provides an improved and comprehensive understanding of the lower Atoka deepwater system and has implications for deciphering the tectonic–sedimentary relationships in laterally confined submarine fan systems.

Diversity of zircon U-Pb geochronology of meta-sedimentary rocks from the Gaixian Formation, South Liaohe Group, Jiao-Liao-Ji belt: Implications for different provenance and crustal evolution

Comprehensive studies of depositional age and source material of the Liaohe Group are significant to the tectonic evolution of the Jiao-Liao-Ji Belt (JLJB). The Gaixian Formation is widely distributed and stratigraphically defined as the uppermost formation of the Liaohe Group. However, our new work reveals that not all meta-sedimentary rocks of the Liaohe Group deposited before the late Paleoproterozoic orogeny. Based on the geochronological results, these meta-sedimentary rocks can be subdivided into two categories. Detrital zircon from the category A meta-sedimentary rocks yield U-Pb age peaks at ca. 2.50 Ga, 2.18 Ga and 2.06 Ga. The youngest age peak of ca. 2.06 Ga, together with the metamorphic age of 1.95–1.84 Ga yielded by pervious studies, indicate their depositional ages of 2.06–1.95 Ga. Compared to the category A, detrital zircon from the category B yield similar 207Pb/206Pb age peaks at ca. 2.54 Ga, ca. 2.17 Ga and ca. 2.05 Ga, but importantly also at ca. 1.87 Ga which was never observed for the category A. The late Paleoproterozoic zircon (~1.87 Ga) include magmatic cores and weakly oscillatory zoned or unzoned rims. These rims yield two age peaks of ca. 1.88 Ga and ca. 1.80 Ga, which are interpreted as inherited partial melting ages. Therefore, the category B meta-sedimentary rocks deposited at some time after ca. 1.80 Ga. These new geochronological data reveal that the category B meta-sedimentary rocks are significantly different with those from the traditional Gaixian Formation. In combination with regional stratigraphy data, it is recommended that the category B meta-sedimentary rocks should be ascribed to the Changhai Group rather than the Liaohe Group.

Geomorphological Approach to Cliff Instability in Volcanic Slopes: A Case Study from the Gulf of Naples (Southern Italy)

This paper deals with the problem of cliff stability and proposes a geomorphological zonation of a cliff using a sector of the Posillipo promontory (named the Coroglio-Trentaremi sea cliff, Italy), in the Campi Flegrei coastal area, as a case study. A detailed geological and geomorphological analysis was carried out, by combining field work with analysis of detailed scale topographic maps, orthophoto, and stratigraphical data from deep boreholes. Field and borehole data, together with structural data collected in seven different stations along the cliff, allowed us to derive six geological cross-sections and to reconstruct the complex stratigraphical and structural setting of the cliff. Geomorphological analysis focused on the detection of the main geomorphological factors predisposing to cliff instability. We selected the most significant factors and divided them into two groups: factors influencing landslide intensity and factors influencing cliff instability. Then, by means of a heuristic approach, we constructed a matrix that was used to derive a map showing the geomorphological zonation of the sea cliff. This map may enable to development of a reliable scenario of cliff instability and consequent retreat, which may be useful either to plan intervention works in the most critical areas or to organize prevention plans aimed at risk mitigation.

FIRST RECORD OF OSTRACODS IN THE ESTIVA FORMATION (PERNAMBUCO BASIN, UPPER CRETACEOUS), NORTHEAST OF BRAZIL

O presente trabalho trata do primeiro registro de ostracodes na Formação Estiva, Bacia Pernambuco (Poço Cupe, 1 LABIO-PE1). A Bacia Pernambuco estende-se por todo o litoral sul do Estado de Pernambuco e está delimitada pela Zona de Cisalhamento de Pernambuco, a norte, e pelo Alto de Maragogi, a sul. A Formação Estiva é composta por carbonatos plataformais, datados como Cretáceo Superior. A análise e interpretação dos dados foram realizadas através de revisão bibliográfica, levantamentos de dados estratigráficos e coleta de amostras. A metodologia adotada para o tratamento das amostras estudadas consistiu na coleta, pesagem e desagregação de amostras; lavagem e secagem do material desagregado e triagem dos microfósseis carbonáticos. Foram registrados raros ostracodes, tentativamente atribuídos ao gênero mixohalino Fossocytheridea Swain & Brown, 1964. O reconhecimento da fauna de ostracodes e sua paleoecologia tem como objetivo contribuir na compreensão da evolução da Bacia Pernambuco.

Solving the puzzle of mercury fate and emissions by coal-fired power plants: The potential of hydrodynamic-atmospheric modelling

There is currently a significant gap in knowledge about the emission and deposition of mercury (Hg) from coal-fired power plants in Australia. To fill this gap, we propose a novel method that combines several sources of information (stratigraphic data, hydrodynamic modelling and atmospheric modelling), to identify the sources and fates of Hg emitted from coal-fired power plants. The stratigraphic record from Lake Macquarie (Australia) shows that mercury deposition increased up to 7-times since the 1950s, which is when coal-fired power plants were commissioned in the catchment. The stratigraphy also shows a decrease in Hg deposition with power plant retrofits. Using results from multiple models (statistical modelling, hydrodynamic modelling, particle density modelling and atmospheric emissions modelling), we found that ash dams contribute little Hg to Lake Macquarie. Instead, most of the Hg contamination in the lake is a result of atmospheric emissions from the power plants, and these power plants are also depositing Hg in the urban areas to the west of the lake. Our results demonstrate that the multi-proxy approach demonstrated in the paper can be used to provide clues as to the source of Hg, so that appropriate mitigation strategies and regulatory frameworks can be implemented.

Mercury atmospheric emission, deposition and isotopic fingerprinting from major coal-fired power plants in Australia: Insights from palaeo-environmental analysis from sediment cores

Despite Australia's high reliance on coal for electricity generation, no study has addressed the extent to which mercury (Hg) deposition has increased since the commissioning of coal-fired power plants. We present stratigraphic data from lake sediments in the Hunter Valley (New South Wales) and Latrobe Valley (Victoria), where a significant proportion of Australia's electricity is generated via coal combustion. Mercury deposition in lake sediments increased in the 1970s with the commissioning of coal-fired power plants, by a factor of 2.9-times in sediments of Lake Glenbawn (Hunter Valley) and 14-times in Traralgon Reservoir (Latrobe Valley). Sediments deposited after the commissioning of power plants have distinct Hg isotope compositions, similar to those of combusted coals. Mercury emission, estimated using an atmospheric model (CALPUFF), was higher in the Latrobe Valley than in the Hunter Valley. This is a result of higher Hg concentrations in lignite coal, lax regulation and older pollution-control technologies adopted by coal-fired power plants in the Latrobe Valley. Near-source deposition of Hg in Australia is significantly higher than North America and Europe, where better emission controls (e.g. wet flue gas desulfurization) have been in effect for decades. The challenge for Australia in years to come will be to ratify the Minamata Convention and develop better regulation policies to reduce Hg emissions.

The first intra-oceanic island-arc porphyry Cu (Au) deposit in the western Bangong-Nujiang suture zone: Evidence from the Saidengnan Cu (Au) deposit

The Saidengnan deposit, located in the Bangong-Nujiang suture zone, is proposed to be the first intra-oceanic island-arc porphyry Cu (Au) deposit in the Bangong-Nujiang metallogenic belt. The Cu (Au) mineralization is hosted in the quartz diorite porphyry as fine grained disseminated form. Zircon U-Pb ages of the ore-forming quartz diorite porphyry and the post-mineralization granodiorite are 118.1–118.8 Ma and 116.2 Ma, respectively, suggesting that mineralization occurred in the Early Cretaceous. The S isotopes (δ34S = −3.8 to −1.5) of ore sulfides and H-O isotopes (δD = −99‰ to −89.9‰, δ18OH2O = 4.9–9.4‰) of ore-bearing quartz veins indicate that the ore-forming fluids was sourced from the ore-forming intrusion. All intrusive rocks are enriched in light REE and LILE (Rb, K) and depleted in HFSE (Ni, Ta, Ti), similar with the island-arc magmas. Whole rock (87Sr/86Sr)i values (0.7040–0.7056), εNd(t) values (−0.35 to 1.94), and significantly positive zircon εHf(t) values (7.37–11.38) and young TDM2 of zircon Hf (455–705 Ma) indicate that the Saidengnan intrusive rocks are dominantly derived from mantle wedge metasomatized by subducted fluids and sediments. This is different from the Duolong continental arc magmas formed by crust-mantle mixing. Combined with stratigraphic data published, we propose that the Saidengnan porphyry Cu (Au) deposit should be formed in the intra-oceanic island-arc setting caused by the oceanic-oceanic subduction of the Bangong-Nujiang Ocean.

Geodynamic environment of the ca. 3800 Ma Outer Arc Group, Isua (Greenland)

The arcuate, 35 km long Isua supracrustal belt (ISB, southern West Greenland) contains the world9s largest remnants of Eoarchean volcanic and sedimentary sequences. The ISB is broadly divided into: (i) the northern <i>Inner Arc Group</i> of 3720 to 3690 Ma rocks, and (ii) the southern <i>Outer Arc Group</i> of <i>ca.</i> 3800 Ma rocks which is bounded on its northern side by the highly tectonized <i>ca.</i> 3750 Ma <i>Dividing Sedimentary Unit</i>. The boundary between the two groups is a mylonite formed between 3685 and 3660 Ma. Despite the generally high strain, amphibolite facies metamorphism and layer-parallel dislocations that can thin or altogether excise some units, domains of lower deformation comprising ≪1% (qualitative assessment) of the Outer Arc Group contain relict sedimentary and igneous structures. Combined with zircon U-Pb geochronology and whole rock geochemistry, this enables the Outer Arc Group lithological sequence and geodynamic setting to be reconstructed. The lower part of the Outer Arc Group is dominated by metabasaltic amphibolites of the <i>Mafic Volcanic formation</i> in which rarely-preserved pillow structures indicate both their predominantly subaqueous eruption and also their stratigraphic facing. They erupted &gt;3800 Ma, because they were first intruded by subconcordant sheets of fine-grained hypabyssal tonalite dated at 3803±3 Ma (Crowley, 2003) and then by coarser-grained 3795 to 3791 Ma tonalite-granodiorite, which forms a large deformed pluton along the south side of the ISB. This formation is succeeded by the <i>Sedimentary formation</i> whose base consists of discontinuous rare, thin fuchsitic quartzites with 3890 to 3805 Ma detrital zircons. Overlying is a diverse package of dolostones, marls and siliceous rocks. Although they are extensively modified by metamorphism and metasomatism, producing widespread growth of talc or tremolite, relict graded sedimentary layering, chemical and isotopic signatures indicate originally sedimentary protoliths. Detrital zircons in these rocks range in age from <i>ca.</i> 3820 to 3805 Ma. This unit shows an upwards transition from ‘pure9 chemical sedimentary rocks with distinct seawater-like trace element signatures into lithologies increasingly contaminated by felsic material that is locally preserved as graded layers, which are interpreted as an increasing volcanogenic input. Succeeding the sedimentary rocks is the <i>Felsic Volcanic formation</i>, an extensive unit of mostly schistose 3807 to 3802 Ma felsic potassic-altered rocks with carbonate-rich interludes and veins. Locally-preserved andesitic units with graded layering, massive vesicular lavas, polymict breccias, resorbed quartz phenocrysts and fiammé, attest to volcanic and volcano-sedimentary protoliths. Whole rock geochemistry and oxygen isotope analyses on these rocks and their zircons indicate predominantly felsic volcanic protoliths that experienced massive alteration in a surficial environment, probably following subaerial eruption. Massive volcanic rocks are commonest in the west of the ISB, suggesting this part of the belt was proximal to a volcanic center. Using these stratigraphic data, we conclude that the ISB volcanic and sedimentary rocks formed in a mobile geodynamic regime resembling plate tectonics, and not within a stagnant lid regime.

Monumental Structures and Volcanic Activities: Excavating the Campana at San Andrés in the Zapotitán Valley, El Salvador

This article presents stratigraphic data and radiocarbon dates combined with Bayesian modeling from San Andrés in the Zapotitán Valley, El Salvador, focusing on the Campana Structure, the largest and longest-used monumental structure at the site. These data refine the regional chronology of the valley and provide insights into the emergence, development, and abandonment of this pivotal center in southeastern Mesoamerica and its potential links to three related volcanic eruptions: Ilopango, Loma Caldera, and El Boquerón. These distinct volcanic events had pronounced effects on local people who innovated new monumental construction projects and used new volcanic debris as construction material after major eruptions. It is suggested that these monumental public building projects played an important role in the post-disaster recovery of societies by helping foster a sense of corporate identity. The use of volcanic material in constructions at San Andrés and the building of these massive structures may also have helped keep these events alive in the communal memory.

Tephrochronological constraints on the timing and nature of sea-level change prior to and during glacial termination V

Glacial-interglacial variations in ice volume and sea level are essential components of the Pleistocene global climate evolution. Deciphering the timing of change of these key climate parameters with respect to the insolation forcing is central to understanding the processes controlling glacial terminations. Here we exploit the sensitivity of the Paleo Tiber River (central Italy) to sea-level forced changes in the base level and the frequent occurrence of datable tephra layers in its sedimentary successions to reconstruct the timing of the relative sea-level (RSL) change between 450 and 403 ka, i.e., across the glacial termination (T-V) that marks the transition between Marine Isotope Stage (MIS) 12 and MIS 11. The analysis hinges on new stratigraphic data, tephra geochemical fingerprinting, and 40Ar/39Ar dating from a fluvial section that represents the inland counterpart of the near mouth, coastal aggradational successions of the San Paolo Formation (SPF). Tephra correlation indicates that the morpho-stratigraphic record of the inland section is as sensitive to the sea-level change as its coastal counterparts, which makes it ideal to complement previous RSL reconstructions from the Tiber River catchment basin, thereby providing a more detailed picture of the sea-level history across T-V. Combined sedimentological and morphological proxies of the composed inland-coastal SPF record document the occurrence of two phases of relatively rapid sea-level rise, here interpreted as meltwater pulse (MWP) events. The earlier MWP occurred between ∼450 and ∼445 ka and matches a relatively minor episode of the sea-level rise documented in an existing RSL record, while the younger MWP at ∼430 ka corresponds to the high amplitude sea-level rise that marks T-V. We find that both MWPs coincide with episodes of ice-rafted debris deposition in the North Atlantic (Heinrich-like events) and with attendant Southern Hemisphere warming, plausibly associated with the bipolar seesaw.

Paleo‐thermal constraints on the origin of native diagenetic sulfur in the Messinian evaporites: The Northern Apennines foreland basin case study (Italy)

AbstractRecent studies on the genesis of sedimentary native sulfur deposits indicate diagenetic mid‐low temperature Bacterial Sulfate Reduction (BSR) as the main process, involving organic compounds (kerogen/hydrocarbons), bacterial colonies and gypsiferous rocks. In the peri‐Mediterranean area (Southern Spain, Sicily, Northern Apennines, Israel), the main sulfur accumulations are always associated with late Miocene sulfates and organic‐rich successions encompassing the Messinian salinity crisis (MSC). In particular, the Messinian successions of the Apennine‐Adriatic foreland basin system, due to a large amount of high‐resolution stratigraphic data, represent a perfect case study for understanding the diagenetic conditions controlling the development of the BSR process during sedimentary basin evolution. In this work, thermal models performed in three sub‐basins in a sector of the Northern Apennines comprised of the Sillaro and Marecchia rivers (Italy), calibrated by means of organic and inorganic geothermometers, indicate a general thermal immaturity of the studied successions attained as a result of a constant heat flow similar to the present day one (ca. 40 mW/m2) since Late Tortonian and lithostatic loads between 615 and 1,710 m depending on different sub‐basins. These results suggest that the MSC deposits experienced maximum temperatures between about 39°C and 65°C. Temperatures derived from thermal models have been used to constraint occurrence of the diagenetic BSR associated with evaporitic deposits providing thermal constraints in sulfur genesis as well as new useful thermal‐constraints for basin analysis studies.

CHRONOLOGY AND PERIODIZATION OF THE VOLGA-DON BABYNE CULTURE

The article is devoted to establishing the chronology and periodization of the Volga-Don Babyne culture, which is the eastern part of the Babyne cultural circle. VDBC has changed from a «Krivaya Luka cultural group» to a full-fledged culture. An important contribution to this process was made by V. V. Otroshchenko. The basis for establishing the chronology and development of the periodization of VDBC are stratigraphic data, the presence of narrowly dated categories of inventory and a series of radiocarbon dating. Stratigraphic data show that the burials of the VDBC in the mounds follow the catacomb and Poltavka mounds and are covered by the tombs of the beginning of the Late Bronze Age. This fact allows us to date it to the end of the Middle Bronze Age. The sequence of cultures in the Lower Volga region is catacomb / Poltavka — VDBC — chariot cultures. There is a series of stratigraphic connections between the burials of post-catacomb cultural formations, where Babyne burials overlap the Lola ones and vice versa. This also confirms the dating of the VDBC within the post-catacomb horizon. Due to the presence of narrowly dated categories of inventory in the VDBC inventory complex (buckles, a bar with two constrictions, crates, set-arrow-makers, petal and horn beads, a bronze cap of Caucasian origin, etc.) it is possible to develop a two-stage periodization of the culture. Most of the diagnostic inventory belongs to the early stage. Two periods of VDBC correspond to two phases (early and advanced) of the post-catacomb block development. VDBC can be synchronized with the first and second stages of the Lola culture and DDBC, as well as with the first stage of the DPBC. The VDBC radiocarbon database contains 18 dates, of which 7 are AMS dates. All of them show a good degree of convergence, which makes it possible to date the culture of the XXII—XX centuries BC. Comparison of this series with 14C data from the other Babyne cultures and the Lola cultural circle confirms the established synchronization lines.

Structural pattern along the course of the Nile Valley opposite El-Balyana, Upper Egypt, using gravity and magnetic data

The main objectives of this study are to evaluate the subsurface structure of the Nile Valley and construct the tectonic regime that shows the main compressive stresses influencing the area using magnetic and gravity methods. To achieve the objectives of the study, the available geophysical data were analyzed qualitatively and quantitatively. The qualitative interpretation focused on describing the distribution and extension of the anomalies in Bouguer anomaly and RTP maps in addition to the derivate maps, while the quantitative interpretation was used to determine the depth of the basement surface which reflects the thickness of the overlain sedimentary cover using the results of 2D and 3D inversion modeling of aeromagnetic and gravity data along some profiles defined in the trending region in the NW-SE, N-S, and E-W directions. The outcomes of 2D and 3D of aeromagnetic and gravity models were verified by real subsurface information obtained from deep well stratigraphic data. The depth to the basement throughout the study area ranges from 0.4 to more than 1.8 km. The structural contour map for the top of the basement indicates that the course of the Nile Valley is affected by subsidence while its eastern and western parts are characterized by series of uplifts. The main structures influencing the study area have bearings NW, representing the Gulf of Suez direction, NE and NNW.

Kort om Sigtunafynden av medeltida klädesplomber

Medieval Cloth Seals from Sigtuna. A brief account of ten medieval cloth seals from the town of Sigtuna, Sweden. Seven seals are from excavations in 1996 and 1999–2000. Three are older finds. The origins of two can be confirmed as Poperinge and Tournai, both towns in the historical Flandres region well-known for producing and exporting cloth from the 13th to the 16th centuries. The other seals could not be firmly identified but are discussed with regards to imagery and alternative provenances. Stratigraphical dating of the find context, where possible, is from the late 13th to 15th centuries. The seals are testimony of trade and import of high quality textiles. However, judging from these finds only, little can be said about possible quantities.

Paleogenomics illuminates the evolutionary history of the extinct Holocene \u201chorned\u201d crocodile of Madagascar, Voay robustus

Ancient DNA is transforming our ability to reconstruct historical patterns and mechanisms shaping modern diversity and distributions. In particular, molecular data from extinct Holocene island faunas have revealed surprising biogeographic scenarios. Here, we recovered partial mitochondrial (mt) genomes for 1300–1400 year old specimens (n = 2) of the extinct “horned” crocodile, Voay robustus, collected from Holocene deposits in southwestern Madagascar. Phylogenetic analyses of partial mt genomes and tip-dated timetrees based on molecular, fossil, and stratigraphic data favor a sister group relationship between Voay and Crocodylus (true crocodiles). These well supported trees conflict with recent morphological systematic work that has consistently placed Voay within Osteolaeminae (dwarf crocodiles and kin) and provide evidence for likely homoplasy in crocodylian cranial anatomy and snout shape. The close relationship between Voay and Crocodylus lends additional context for understanding the biogeographic origins of these genera and refines competing hypotheses for the recent extinction of Voay from Madagascar.

Grid mapping revealed hidden geochemical lens and its chemostratigraphic bias in the middle‐upper Permian marine carbonate sequence in Laibin, South China

Deep‐time chemostratigraphy provides important data for stratigraphy and palaeoenvironmental reconstruction. Geochemical analysis for the same proxy from the same outcrop section, however, often results in different data among various researchers. The dispute was ascribed to inappropriate screening of samples weathering, pre‐treatment, and analytical methods. An outstanding example is that a great variation of 1–3‰ in δ13CVPDB values from the same horizons at Auxiliary Global Stratotype of Section and Point for the Guadalupian–Lopingian (G‐L) boundary in Tieqiao, Laibin, South China was obtained by various research groups. The Walther's Law of Facies suggests that such differences in analytical results may be due to the diachronism of samples measured in high‐resolution stratigraphy. Although lithology and broad sedimentary facies are the same in a lithostratigraphic unit, heterogeneous distribution of bioclastics, δ13Corg, provenances, trace elements, and age‐controlling geochemical signals might have printed on sediments within the same bed. Here, we verified the variations by grid mapping and sampling, a new method for high‐resolution chemostratigraphy, and this practice is applied to the auxiliary GSSP at the Tieqiao section. A total of nine parallel columnar sections from the upper Guadalupian to lowest Lopingian were measured and sampled. In addition, four lateral profiles along four beds were also sampled, and two of them are close to the lower part of the section (upper Guadalupian) and near the G‐L boundary, respectively. These analytical results are plotted along the coordinate of X–Y axis and form the grid mapping on the outcrop. Contour maps of various proxies (i.e., CaO%, total Fe%, and δ13Ccarb) based on the grid mapping were constructed on the outcrop, instead of single excursions of various geochemical proxies throughout the upper Guadalupian to lowest Lopingian. The results show different negative excursions of δ13Ccarb coinciding with biotic extinction near the G‐L boundary and answered the differences of proxy reported in previous studies. Grid mapping of various proxies shows general trends of the proxies on the outcrop; however, there are invisible beddings across lenses in dozens meters size of geochemical abnormal. Analytical data of the same proxy from the same horizons at different columnar sections may present different excursions if sampling on the abnormal lenses or not. This is why the data are different among various studies when different columnar sections were sampled. Various lenses of geochemical abnormal which may be linked tectonic controlled diagenesis, and microhabitat et al., and resulted in the bias from different columnar sections were sampled.

REVENIA-KORINOS: ONE OF THE EARLIEST NEOLITHIC SETTLEMENTS IN NORTH GREECE AS EVIDENCED BY RADIOCARBON DATING

ABSTRACTRadiocarbon (14C) dating was applied to the Neolithic open-air, flat-extended settlement at Revenia-Korinos in Pieria, North Greece. The samples came from the earlier habitation period of the settlement, characterized by more than 100 pits that vary significantly in shape and dimensions, some of them being identified as subterranean or semi-subterranean pit dwellings. It is suggested that the fills of the pits were the result of secondary, structured refuse deposition, except for pits that preserve their habitational use, according to stratigraphic data. The 14C results confirm that Revenia is among the earliest Neolithic settlements in North Greece and the Aegean in general. The initial phase of habitation is dated at around 6600/6550 BC comparable only to two other EN sites in North Greece. Habitation intensified at around 6460/6430 BC, accompanied by a shift in pottery style. This phase lasts until 6200/6100 BC when the pit habitation mode is followed by above-ground, rectangular post-framed structures. The dates of the human burials from Revenia also identify them as among the earliest Neolithic burials in Greece. Finally, the radiocarbon dates proved very useful for sequencing the chronological use of the pits and the excavated area in general.

THE BEGINNING OF THE IRON AGE AT ARSLANTEPE: A14C PERSPECTIVE

ABSTRACTThe Iron Age chronology at Arslantepe is the result of the interpretation of Luwian hieroglyphic inscriptions and archaeological data coming from the site and its surrounding region. A new round of investigations of the Iron Age levels has been conducted at the site over the last 10 years. Preliminary results allowed the combination of the archaeological sequence with the historical events that extended from the collapse of the Late Bronze Age empires to the formation and development of the new Iron Age kingdoms. The integration into this picture of a new set of radiocarbon (14C) dates is aimed at establishing a more solid local chronology. High precision14C dating by accelerator mass spectrometry (AMS) and its correlation with archaeobotanical analysis and stratigraphic data are presented here with the purpose of improving our knowledge of the site’s history and to build a reliable absolute chronology of the Iron Age. The results show that the earliest level of the sequence dates to ca. the mid-13th century BC, implying that the site started developing a new set of relationships with the Levant already before the breakdown of the Hittite empire, entailing important historical implications for the Syro-Anatolian region at the end of the 2nd millennium BC.

Asynchronous δ13Ccarb and δ13Corg records during the onset of the Mulde (Silurian) positive carbon isotope excursion from the Altajme core, Gotland, Sweden

High-resolution paired analyses of δ13Ccarb and δ13Corg from a new drill core from Gotland, Sweden, demonstrate asynchronous positive change in the carbon isotope records during the onset of one of the major Silurian biogeochemical events known as the Mulde Event or “Big Crisis”. The detailed carbon isotope record presented here provides Δ13C (the difference between δ13Ccarb and δ13Corg) and allows the calculation of changes in organic carbon burial (forg) throughout the late Wenlock. The paired data suggest a ~ 38% increase in forg during the peak of the positive δ13Ccarb excursion and the high-resolution record reveals several short-lived inflections in Δ13C that have not been previously identified. When combined with sedimentological and sequence stratigraphic data from multiple paleocontinents, the new data presented here provide strong evidence for a transient global decrease in CO2, in support of previous interpretations of regression and global cooling coinciding with the Mulde Extinction Event.

Geochemical, geochronological, and isotopic constraints for the Archean metamorphic rocks of the westernmost part of the Carajás Mineral Province, Amazonian Craton, Brazil

The Archean nucleus of the Amazonian Craton, represented by the Carajás Mineral Province (northern Brazil), crops out as a broad exposition of igneous, sedimentary, and metamorphic rocks showing a complex polyphase geologic history. A succession of orthogneisses (metagranitoids), amphibolites, and metavolcano-sedimentary rocks that show greenstone belt characteristics occur in Tancredo Neves Village district, northeast of São Félix do Xingu city (state of Pará), is the focus of this study. Detailed field, petrographic, and stratigraphic data reveal that these metamorphic rocks underwent two different tectono-metamorphic events: (i) the regional metamorphism (>2.8 Ga), which occurred under greenschist-to mid-upper amphibolite-facies conditions; and (ii) the dynamic metamorphism (>2.6 Ga) which reached amphibolite-facies conditions and overprinted previous metamorphic textures. Associated regional strike-slip NW–SE to EW-trending ductile shear zones generated mylonitic, ultra-mylonitic, and migmatitic zones. Whole-rock geochemistry discriminates four groups of metagranitoid protoliths. G1 group is composed of peraluminous trondhjemitic rocks samples, calc-alkaline, weakly fractionated, and enriched in HREE. G2 group comprises metaluminous and alkaline monzogranite samples with high Zr, Y, Nd, HREE, and intermediate fractionation. U–Pb (LA-MC-ICP-MS) dating of G2 zircons yields a crystallization age of 2745.6 ± 5.0 Ma. Groups G3 and G4 encompass peraluminous, calc-alkaline to alkali-calcic, anorogenic, fractionated monzogranitic and granodioritic rocks. G3 and G4 groups are further distinguished by high and low La/Yb(N) ratios, respectively. The results obtained for Tancredo Neves Village district very much resemble the Canaã dos Carajás (Carajás Mineral Province) area characteristics, comprising intense magmatism (2.7–3.0 Ga) and reworking related to at least two distinct metamorphic events in the Archean. As Canaã dos Carajás, Tancredo Neves Village can be a promising area for mining exploration.