Ancient Examples Research Articles

Facies variations in gravelly cyclic steps deposited from turbidity currents: Miocene fan delta front deposits compared with a modern active fan delta, central Japan

AbstractGravelly cyclic steps formed by turbidity currents have recently been widely recognised in the geological record. However, the comparison between modern and ancient gravelly cyclic steps remains challenging. In this study, the facies variations of gravelly cyclic steps deposited from turbidity currents in an outcrop of Miocene fan delta front deposits in central Japan are compared with the geomorphic evolution of analogous cyclic steps on the active fan delta front in modern geological systems. These cyclic steps share common characteristics in setting, grain size and dimensions, allowing direct comparison between ancient and modern examples. Repeat bathymetric surveys of the modern Kurobe River fan delta have revealed various types of upslope migrating bedforms interpreted as cyclic steps. Most of these are short‐lived due to erosion of thalwegs by powerful surge‐type turbidity currents triggered by slope failures or burial of thalwegs by deposition, possibly from river‐fed hyperpycnal flows. Such erosion and burial events occur annually on the fan delta front, resulting in compensational cycles. Sedimentary facies of the Miocene fan delta front deposits include conglomerate with a gently upslope dipping erosional base, backset‐stratified sandstone and foreset‐stratified sandstone, which are interpreted as deposits of hydraulic jumps in high‐density turbidity currents in scours on the stoss sides of cyclic steps. Parallel‐stratified conglomerate sandstone is an additional component. Although previous facies models of gravelly cyclic steps have focussed on deposits on stoss sides, a comparison of modern and ancient examples suggests that facies on the lee sides could be parallel‐stratified conglomerate sandstone and undulating bedforms, reflecting supercritical flow conditions. The present study also suggests that hyperpycnal and surge‐type high‐density turbidity currents may deposit different types of facies and play different roles in the construction and destruction of cyclic steps. The present study has significant implications for facies models of gravelly cyclic steps.

Giant sediment-wave field and supercritical flows in a distally steepened ramp, Fort Payne Formation (Lower Mississippian), Kentucky–Tennessee, U.S.A.

ABSTRACT Sediment waves are common in confined to unconfined settings on modern marine slopes and basin floors worldwide. Their morphology and stratal patterns show that many of them migrate upslope and upflow, a characteristic thought to record Froude-supercritical flow conditions associated with sediment gravity flows and density cascades. Few sediment waves of this type have been observed in the ancient rock record. This study reports the discovery of a giant (> 20,000 km2) sediment-wave field in Lower Mississippian carbonates and shales of the Fort Payne Formation in Tennessee and Kentucky, U.S.A. Sediment waves are present in the clinothem slopes and basin floor of a distally steepened ramp as seismic-scale bedforms ranging from 100 to 700 m long and 15 to 50 m high. Dominant facies include crinoidal shales, packstones, and rudstones. Many of the beds are sharp-based and graded, indicating sediment-gravity-flow deposition. Upslope-inclined rudstones (backsets) and wavy beds with upflow and downflow laminae are common and indicate supercritical flow conditions. These observations and interpretations are in stark contrast to previous interpretations of crinoidal bioherms and Waulsortian-type mounds. Basin physiography, a cool-water heterozoan carbonate factory and coastal upwelling were key factors in establishing a rapidly prograding ramp characterized by high rates of sediment production and basinward shedding. Sediment gravity flows and density cascades transported crinoidal grains downslope and entrained crinoids that inhabited the slope. Flows frequently reached Fr-supercritical flow conditions that led to the formation of sediment waves similar to those on modern marine slopes. This sediment-wave field is one of the first to be documented in the ancient rock record, and its extent is enormous. The near absence of other reported ancient examples must be due to misinterpretation (mounds, slumps) and the problem of observational scale and resolution. Sediment waves are often larger than outcrops. Lack of recognition of sediment waves in subsurface seismic sections is probably due to misinterpretation and insufficient resolution. Perhaps this study demonstrates the need for revisiting and updating existing facies models of carbonate-sediment transport and depositional processes across slopes and basin floors.

Is the Mesoarchean Mulgandinnah shear zone, Pilbara Craton, the world's oldest arc-slicing transform fault?

Abstract Arc-slicing transform faults represent an integral component of convergent margin tectonics. They are developed above oblique subduction systems, cutting through and displacing the entire magmatic section of arcs, leading to tectonic repetition of segments of the overriding plate in the ensuing orogenic collage. Extant examples clearly show this process in Sumatra, New Zealand, and the Philippines, while ancient examples are reported from the Paleozoic Altaids and Neoarchean Superior and Yilgarn cratons. Here, we report data that document that the Paleo-Mesoarchean Eastern Pilbara craton, recently interpreted to be a preserved mid-upper crustal level of a magmatic arc, is cut and repeated by a major 3.0–2.93 Ga arc-slicing fault, the Mulgandinnah, which sliced a previously 600 × 100 km segment of a Mesoarchean arc system, laterally moving different segments to their presently juxtaposed 200 × 200 km preserved fragment. This evidence demonstrates lateral plate motions by 3.0 Ga and shows oblique subduction, arc plutonism, arc-slicing, and repetition, reflecting that crustal growth in modern-style convergent margins was in full operation by the Mesoarchean.

Paired Metamorphism of SW Japan and Implications for Tectonics of Convergent Margins

The Sanbagawa-Ryoke pair of geological units in southwest Japan is the classic example of paired metamorphism originally identified by Akiho Miyashiro. Together these belts represent an important study area for developing and testing ideas about how convergent margins behave over geological time based on studies of the rock record including petrology, geochemistry, deformation, and geochronology. The two sides of the pair represent ancient examples of a subduction zone in the Sanbagawa belt and an associated volcanic arc in the Ryoke belt. This issue of Elements brings together the results of a wide range of different approaches summarizing the current state of knowledge about the Sanbagawa-Ryoke pair and how this informs our understanding of convergent margins in general.

Significance of a Mesoproterozoic tide-reworked fan delta – tidal flat transition: A transgressive-regressive model

Records of tide-reworked fan delta facies models are rare in literature, attributed to their lower abundances due to complex sediment distribution pattern by two exclusive end-member flows, viz., a seaward directed subaerial to subaqueous debris flow, and dominant tidal current system interfering with and reworking the debris flow. Lack of appropriate analogues of tide-reworked fan deltas makes the ancient examples more significant. The analysis of such rare tide-reworked fan deltas from deep-time, e.g., Mesoproterozoic, turns out to be unique due to the gap in clear understanding of the alluvial-fluvial vs marine processes in non-vegetated land parts. The lower part of the Mesoproterozoic Rajgarh Formation, Lalsot Basin, North Delhi Fold Belt, Aravalli Craton in NW India, provides a rare record of a tide-reworked fan delta depositional system. Sedimentary facies analysis reveals eleven lithofacies grouped under three major facies associations, viz., (i) gravel-rich conglomerate facies association, characterized by stacked debris flow deposits forming a subaerial alluvial fan, representing the delta topset component, followed downslope by (ii) pebbly, cross-stratifed sandstone facies association, characterized by reworking of the subaqueously emplaced debris flows by ebb-tidal currents, to produce the mouth bar and the delta front depositional systems, and finally, (iii) sandstone-mudstone heterolithic facies association, characterized by abundant tidal signatures in pebble-free thin-bedded sandstone-mudstone heteroliths with tidal bundles, herringbone cross-strata and wave ripples, characterizing a stable platformal subtidal-intertidal flat depositional system. The lower-middle part of the succession records an aggradational stratal stacking pattern of the subaerial alluvial fan changing to progradational stratal stacking of the laterally accreted debris-rich tide-led clinoforms producing the delta topset – mouth bar – delta front transiton of a tide-reworked fan-delta under successive regressive conditions, representing syn-rift deposition near the basin margin. A retrogradational stratal stacking pattern overlies the fan-delta succession, and signifies a transgression by landward encroaching tidal flat system over the fan-delta system during post-rift phase in a stable platformal setup, where debris supply is ceased. A regressive-transgressive model characterizing the transition from a fan-delta to tidal flat depositional systems portrays fluctuations in the accommodation conditons in response to complex interplay of basin tectonics and relative sea level changes in the Mesoproterozoic riftogenic Lalsot Basin.

Neolithic Liner Dagger from Ust-Narym in the Irtysh River Valley

The present research featured a slotted, or liner, bone dagger from the Neolithic layer of the Ust-Narym settlement on the Irtysh River. Its design, material processing technology, and functional purpose make it a rare, as well as the most ancient example of hand-to-hand combat weapons found in Kazakhstan. This composite object was carved from the posterior left metatarsal bone of a wild auroch with the help of several tools. It includes thin and sharp flint inserts, which were attached into the grooves on the side faces of the dagger frame with a special adhesive substance. An additional nozzle for a short handle made it possible to use this piercing-cutting weapon in battle. It is decorated with dots and circles connected by straight lines, which probably means it was a socialized object of ritual use associated with sacrifice. Typologically, the dagger from Ust-Narym is similar to artifacts found in the Late Paleolithic and Mesolithic sites in the south of Western Siberia, in the Urals, in the Baikal region, and in Eastern Europe. The dagger marks a milestone in the technical and technological development of ancient Eurasian peoples. It also illustrates the ethno-social and cultural processes across the vast territory of Eurasia.

Coarse-grained submarine channels: from confined to unconfined flows in the Colombian Caribbean (late Eocene)

Submarine channel mouth settings are hardly preserved in the stratigraphic record. Although they are still poorly known with respect to other segments of turbidite systems, conceptual models are being refined in the light of new discoveries in modern and ancient examples. Still, some questions such as the transition between expansion zones and the traditional Channel-Lobe Transition Zone (CLTZ) remains open in ancient systems. Upper Eocene deposits of the Colombian Caribbean (San Jacinto Fold Belt) are interpreted here as a fan-delta-fed, submarine, coarse-grained channel-lobe system. It displays a well-preserved channel inception stage in the shelf break represented by sigmoidal to lens-shaped gravels, and planar cross-stratified pebbly sandstones (foreset and backset) interpreted as cyclic steps in an expansion zone. In a later stage, a classical channel-levee complex was developed, represented by channel fill elements showing sharp- and erosional-based, fining-upward sequences that are meters thick, having basal massive matrix-supported pebble conglomerates (hard—extrabasinal—clasts, rip-up clasts, coastal bioclasts), vertically evolving to liquefied massive to planar-laminated coarse-grained sandstones with phytodetrital carbonaceous laminae. They are interpreted as concentrated flow deposits (high-density turbidites) coming from continental areas or from coastal systems (i.e., delta reworking). Undifferentiated channel belt thin-bedded turbidites associated with levees and terraces deposits are related to these confined systems. The channel-lobe transition zone is characterized by debrites from cohesionless debris flow in a channel-mouth bar setting, representing bypass processes that developed distally into low-angle, planar cross- and sigmoidally-stratified (upstream antidune) pebble-size to coarse-grained sandstones that fill low-angle scours (cut-and-fill structures) in an antidune field setting with supercritical conditions. When the currents lose channel confinement, the setting is characterized by changes from Froude supercritical to subcritical flow conditions in an inner lobe to lobe off-axis environment. Large seasonal fluctuations in precipitation favor high sediment concentrations, promoting the formation of volumetrically significant fan deltas and coarse-grained submarine channels with high erosive capacity; therefore, their record helps refine interpretations of depositional processes, providing criteria for recognizing areas of the turbiditic systems that are hardly preserved. The particular aggradational conditions for the preservation and stratigraphic characterization of the rare exhumed submarine channel mouth systems make it possible to decipher sediment dispersal patterns and thus connect the models proposed here, from supercritical systems to the traditional models of turbiditic systems.

Calcidius against Plato’s <em>obscuritas</em> (again)

At a certain point of his commentary on Plato’s Timaeus (317.15 ff. Wazink), Calcidius sets out to distinguish different kinds of obscurity that can affect a text. The first to be analysed is the obscuritas iuxta dicentem: in this case, obscuritas is said to depend on either a decision (studio) made by the author (this was the case of both Aristotle and Heraclitus), or the inefficacy of language (imbecillitas sermonis). Secondly, Calcidius takes into account the obscuritas iuxta audientem, i.e. that particular kind of obscurity which is due to both the novelty and even the oddity of the discourse (cum inaudita et insolita dicuntur), and the intellectual inadequacy of the listener (cum is qui audit pigriore ingenio est ad intellegendum). Thirdly, Calcidius mentions a kind of obscurity which is said to be iuxta rem. In other words, this obscurity is relative to any res (i.e. any object of analysis) which is such that it cannot be precisely and immediately understood. Note that Calcidius takes this to be the case of Plato’s chora: for, neither it can be perceived through the means of sense perception, nor it can be intellectually grasped. But, as Calcidius clarifies, the presence of a certain degree of obscurity in a text does not necessarily put its veritative value at risk, just as the being true of a text does not automatically entail its being clearly expressed (non statim quae vere dicuntur aperte etiam manifesteque dicuntur). Unfortunately, to this ancient example of hermeneutics no extensive study has ever been devoted, as Professor Franco Ferrari has often pointed out. So, my objective is to extensively scrutinise the general classification of obscuritates provided by Calcidius and then to relate it to the Middle Platonic strategies aimed at neutralising Plato’s obscuritas.

Early marine carbonate cementation in a relict shelf-edge coral reef North of Miami, Florida: Pseudo-coupled depositional and diagenetic modeling

Carbonate depositional and early diagenetic processes overlap in time because of the high chemical reactivity of calcite. Previous studies have modeled early diagenesis in a static depositional framework. They followed a rule-based modeling approach instead of applying rigorous thermodynamics and reaction kinetics.This study has developed a pseudo-coupled approach based on a dynamic depositional framework and reactive transport modeling for diagenesis. It has been tested for the “Pompano” reef north of Miami, Florida. The model includes five reef parasequences deposited over 9.0 kyr with five facies zones. After deposition of the first parasequence, diagenetic processes are modeled. The resulting framework forms the starting condition for depositing the next parasequence. Subsequently, its diagenetic overprint and the continued overprint in the underlying parasequence(s) are modeled. These workflow steps are repeated until all five parasequences are covered.The results show the spatial and temporal development of calcite cementation and porosity distribution. During the reef catch-up phase, cement mainly developed at the depositional surface (up to 10% of the total sediment volume). During the keep-up phase, cement abundance increases to a maximum value of ∼17%. After the reef's demise, cement forms a crust at the sediment-water interface with up to 38% of the total sediment volume. In general, controlling factors of cement distribution include facies-specific flow velocities, reef facies, relative sea-level changes, depositional gaps, and seawater salinity.The modeling results of this study are well aligned with the actual cement and porosity distribution in the Pompano reef and with other sub-recent and ancient examples described in the literature. Pseudo-coupled depositional-diagenetic modeling represents a suitable approach for quantitative porosity prediction in comparable depositional and diagenetic settings. It reduces uncertainties in prediction at inter-well to prospect scale for oil and gas exploration, geothermal exploration, and subsurface storage of CO2.

Petrochronologic constraints on inverted metamorphism, terrane accretion, thrust stacking, and ductile flow in the Gneiss Dome belt, northern Appalachian orogen

AbstractGneiss domes are an integral element of many orogenic belts and commonly provide tectonic windows into deep crustal levels. Gneiss domes in the New England segment of the Appalachian orogen have been classically associated with diapirism and fold interference, but alternative models involving ductile flow have been proposed. We evaluate these models in the Gneiss Dome belt of western New England with U‐Th‐Pb monazite, xenotime, zircon, and titanite petrochronology and major and trace element thermobarometry. These data constrain distinct pressure–temperature–time (P‐T‐t) paths for each unit in the gneiss dome belt tectono‐stratigraphy. The structurally lowest units, Laurentia‐derived migmatitic gneisses of the Waterbury dome, document two stages of metamorphism (455–435 and 400–370 Ma) with peak Acadian metamorphic conditions of ~1.0–1.2 GPa at 750–780°C at 391 ± 7 to 386 ± 4 Ma. The next structurally higher unit, the Gondwana‐derived Taine Mountain Formation, records Taconic (peak conditions: 0.6 GPa, 600°C at 441 ± 4 Ma) and Acadian (peak: 0.8–1.0 GPa, 650°C at 377 ± 4 Ma) metamorphism. The overlying Collinsville Formation yielded a 473 ± 5 Ma crystallization age and evidence for metamorphic conditions of 650°C at 436 ± 4 Ma and 1.2–1.0 GPa, 750–775°C at 397 ± 4 to 385 ± 6 Ma. The structurally higher Sweetheart Mountain Member of the Collinsville Formation yielded only Acadian zircon, monazite, and xenotime dates and evidence for high‐pressure granulite facies metamorphism (1.8 GPa, 815°C) at circa 380–375 Ma. Cover rocks of the dome‐mantling The Straits Schist records peak conditions of ~1 GPa, 700°C at 386 ± 6 to 380 ± 4 Ma. Garnet breakdown to monazite and/or xenotime occurred in all units at circa 375–360 and 345–330 Ma. Peak Acadian metamorphic pressures increase systematically from the structurally lowest to highest units (from 1.0 to 1.8 GPa). This inverted metamorphic sequence is incompatible with the diapiric and fold interference models, which predict the highest pressures at the structurally lowest levels. Based upon P‐T‐t and structural data, we prefer a model involving, first, circa 380 Ma thrust stacking followed by syn‐collisional orogen parallel extension, ductile flow, and rise of the domes between 380 and 365 Ma. Garnet breakdown at circa 345–330 Ma is interpreted to reflect further exhumation during collapse of the Acadian orogenic plateau. These results highlight the power of integrating petrologic constraints with paired geochemical and geochronologic data from multiple chronometers to test structural and tectonic models and show that syn‐convergent orogen parallel ductile flow dramatically modified earlier accretion‐related structures in New England. Further, the Gneiss Dome belt documents gneiss dome development in a syn‐collisional, thick crust setting, providing an ancient example of middle to lower crustal processes that may be occurring today in the modern Himalaya and Pamir Range.

Upper-plate response to ridge subduction and oceanic plateau accretion, Washington Cascades and surrounding region: Implications for plate tectonic evolution of the Pacific Northwest (USA and southwestern Canada) in the Paleogene

Abstract The interaction between subduction zones and oceanic spreading centers is a common tectonic process, and yet our understanding of how it is manifested in the geologic record is limited to a few well-constrained modern and ancient examples. In the Paleogene, at least one oceanic spreading center interacted with the northwestern margin of North America. Several lines of evidence place this triple junction near Washington (USA) and southern British Columbia (Canada) in the early to middle Eocene, and we summarize a variety of new data sets that permit us to track the plate tectonic setting and geologic evolution of this region from 65 to 40 Ma. The North Cascades segment of the voluminous Coast Mountains continental magmatic arc experienced a magmatic lull between ca. 60 and 50 Ma interpreted to reflect low-angle subduction. During this period of time, the Swauk Basin began to subside inboard of the paleo-trench in Washington, and the Siletzia oceanic plateau began to develop along the Farallon plate–Kula plate or Farallon plate–Resurrection plate spreading center. Farther east, peraluminous magmatism occurred in the Omineca belt and Idaho batholith. Accretion of Siletzia and ridge-trench interaction occurred between ca. 53 and 49 Ma, as indicated by: (1) near-trench magmatism from central Vancouver Island to northwestern Washington, (2) disruption and inversion of the Swauk Basin during a short-lived contractional event, (3) voluminous magmatism in the Kamloops-Challis belt accompanied by major E-W extension east of the North Cascades in metamorphic core complexes and supra-detachment basins and grabens, and (4) southwestward migration of magmatism across northeastern Washington. These events suggest that flat-slab subduction from ca. 60 to 52 Ma was followed by slab rollback and breakoff during accretion of Siletzia. A dramatic magmatic flare-up was associated with rollback and breakoff between ca. 49.4 and 45 Ma and included bimodal volcanism near the eastern edge of Siletzia, intrusion of granodioritic to granitic plutons in the crystalline core of the North Cascades, and extensive dike swarms in the North Cascades. Transtension during and shortly before the flare-up led to >300 km of total offset on dextral strike-slip faults, formation of the Chumstick strike-slip basin, and subhorizontal ductile stretching and rapid exhumation of rocks metamorphosed to 8–10 kbar in the North Cascades crystalline core. By ca. 45 Ma, the Farallon–Kula (or Resurrection)–North American triple junction was likely located in Oregon (USA), subduction of the Kula or Resurrection plate was established outboard of Siletzia, and strike-slip faulting was localized on the north-striking Straight Creek–Fraser River fault. Motion of this structure terminated by 35 Ma. These events culminated in the establishment of the modern Cascadia convergent margin.

Semantic and Formal Image of Concepts Related to “Sensory Perceptions” Preserved from the Indo-European Language in the Dialect Area

Syunik and Artsakh (Kharabagh) are the greatest dialectical areas in the Armenian language which has a rich vocabulary. In the dialectical vocabulary there are large number of words of Indo-European origin which are missing not only in other dialects but also in many languages of Indo-European origin. One of the problems of comparative linguistics is that etymological studies do not pay much attention to dialectical vocabulary. The study of the words of the thematic group “Sensory Perceptions” can provide important material on the religious-philosophical issues of the peoples living in the historical area. An attempt was made to study the old words of the dialect area of Syunik and Artsakh, which refer to “sensory perceptions”. In this work a new dialectical work is being etymologized: shapaghwith the meaning “1.Reflexion, flash, 2. Ra-diant, bright, shiny” which has a different phonetical and semantical version in the Armenian translation of the “Bible”: shaghpaghp. An attempt was made to check the word simultaneously and to discover its perception in the most ancient examples of the translation of the Bible by using the historical-comparative method. Often, through the etymology of archaisms preserved in the language, valuable information is revealed about the religious-philosophical understandings of the ancient world.

Ethos and Hermeneutics: An Ancient Example of Theories’ Interaction

Ethos and Hermeneutics: An Ancient Example of Theories’ Interaction

Transgressive rocky coasts in the geological record: Insights from Miocene granitic rocky shorelines and modern examples

Rocky shorelines are commonly punctuated, with alternating high relief cliffs and incised embayments which host “pocket beaches”. While multiple cases of ancient rocky shorelines associated with low relief ravinement surfaces have been documented in the geological record, deposits formed in pocket beaches and joint-cut coves are more rarely described. This poses the question “are high relief rocky coastlines and their associated deposits not preserved or have they been previously overlooked? Here we document exhumed examples of ancient granitic rocky shoreline systems of diverse morphologies from the Early Miocene of northern Austria, and compare them with modern systems in UK, Corsica, Spain and Norway. The preserved ancient examples offer a good opportunity to characterize these sedimentary systems, provide diagnostic criteria for their recognition and discuss the main controls on their occurrence and preservation in the rock record.From their stratigraphic and sedimentological analysis, and its comparison with modern examples, we interpret that these rocky shorelines form and get preserved during rapid rates of combined tectonic and eustatic sea-level rise, along lithological, structural and weathered “weakness” zones affected by normal low wave energy conditions interrupted by storms. These results provide a mechanism for predicting their potential occurrence and distribution during transgression of rocky coasts, with implications for exploration around structural highs and coastal management.

Flooding of a carbonate platform: The Sian Kaʼan Wetlands, Yucatán, Mexico—A model for the formation and evolution of palustrine carbonate factories around the modern Caribbean Sea and in the depositional record

AbstractThe dynamic inter‐relationships between marine and freshwater carbonate depositional environments are illustrated in the Sian Ka'an Wetlands, a 5 280 km2 complex of groundwater‐fed freshwater marshes, lakes and brackish coastal lagoons in the South‐East Yucatán Peninsula (Mexico). The Yucatán Platform was subaerially emergent and extensively karstified during the last glacial maximum at 18, 000 yr bp. The Late Holocene transgression has caused progressive reflooding of the continental margin, backstepping of the MesoAmerican Reef and encroachment of coastal environments into the platform interior as rising groundwaters flood an interconnected cave and sinkhole system and feed seasonal marshes above. The Sian Ka'an Wetlands form a vast palustrine carbonate factory which is directly juxtaposed and dynamically linked with the marine carbonate factory to seaward. Continuing sea‐level rise has caused synchronous landward migration of marginal marine and freshwater environments as beach barriers were breached and palustrine sloughs flooded to form marginal marine seagrass lagoons. The Rio Hondo Fault conditions fluid inflow while the sub‐environments of the Sian Ka'an Wetlands reflect tectonic controls on microtopography and hydroperiod. Modern analogues for the Sian Ka'an Wetlands include the Florida Everglades, formed during transgression of the Florida Platform, and relict marsh environments preserved on leeward shores of Andros, Abaco and other Bahama islands. A wide range of ancient examples deposited in coastal and continental interior settings similarly reflect seasonal aquifer rise in response to marine transgression and/or onlap of late‐stage basin fill onto a karstified pediment. Freshwater palustrine carbonate factories on carbonate platforms are transient deposystems, controlled by subtle water depth, climate, vegetation and hydrological factors while being critically sensitive to sea‐level changes and tectonics. The preservation potential of palustrine carbonates may be relatively low in coastal settings due to erosion or shallow marine overprinting, while greater further inland where marine flooding is rarer and in tectonically subsident continental interior basins where accommodation space is continuously created.

Magnetic Signature of Gold Deposits: Example from Um Garayat Region, South Eastern Desert, Egypt

Magnetic methods of exploration have proved to be efficient and have potential in the gold mineralization industry. New magnetic processing technologies aid in improving the process of interpretation and gold opportunity identification. In this work, we show the possible application of combined digital magnetic filters to explore new gold mineralization localities with application to a well-known Au mineralization zone. Um Garayat (UG) region, southeastern desert, Egypt, is an ancient example of a potential area for gold mining. Modern analysis showed that other types of mineral concentrations are present. So, exploiting the magnetic signature of the area for future investment is of great interest. The old UG gold mine is characterized by volcanic and tectonic features such as faulting and folding that affect the arc sedimentary rock sequence of repeated deformation stages. A thorough geophysical effort has been carried out around the old gold mine in the UG area to explore the extension of mineralized ore deposits. A detailed geophysical survey using magnetics was carried out in this study together with the available aeromagnetic data. Field data sets on appropriate sites were measured, processed, and evaluated by suitable software. High magnetic anomalies were detected based on grid filter analysis and contact occurrence maps as marked as possible ore deposits after satisfying the geologic conditions for gold formation. An integrated understanding of attained results revealed that the new possible ore deposits are related directly to fault and fracture zones in the shape of lenses of variable thickness in this zone. Results show that newly detected mineral occurrences in the UG area are also controlled by major faults and hydrothermal solution enrichment along fault zones at a depth ranging from 20 to 70 m. Favorable fault/joint mineralized places were located. The relationship between the Au-quartz vein's strike direction compared with magnetic anomaly lineament analysis was studied. Search for new sources of Au and other mineral deposits in addition to quartz veins is needed as pockets of accumulated mineral-rich rock fragments are deposited in drainage wadis and fault/joint zones because of hydrothermal solution enrichment.

Straits and seaways: end members within the continuous spectrum of the dynamic connection between basins

Abstract Straits and seaways are fundamental connectors of oceans, seas and more rarely lakes. They are ubiquitous in the modern geography and should be common in ancient landscapes. We compare their characteristics to improve our understanding of these features, with the aim to define better their geological use. We review geomorphological, oceanographic, geological and depositional characteristics based on well-documented modern and ancient examples, with a stronger focus on the rock record. ‘Strait’ and ‘seaway’ are differentiated by their spatial and temporal scale. This influences the type and persistence of oceanographic circulation and sediment distribution. Straits are individual depositional systems, with predictable bedform and facies changes along the sediment transport pathway, whereas seaways are larger and longer-lived physiographic domains, composed of numerous depositional systems. Therefore, their stratigraphic signature in the rock record should be significantly different. We conclude that straits and seaways are end members of a continuum, giving rise to the occurrence of intermediate cases with transitional characteristics. The distinctive geological usage of the terms ‘strait’ and ‘seaway’, even without sharp boundaries between end members, may be helpful for predicting their occurrence, stratigraphy, palaeogeography, biota distribution and potential distribution of reservoirs and seals for fossil resources and CO 2 storage.

КОНЦЕПТ ПОЛИТИЧЕСКОГО ТЕЛА ВО ФРАНЦУЗСКОМ ПОЛИТИКО-ФИЛОСОФСКОМ ДИСКУРСЕ XIV В.

Throughout the 14th – 15th centuries, French intellectuals actively used the concept of body politic in their works – in mirrors for princes, sermons, ballads and first political treatises. In this vein, both ancient examples of the construction of such models and medieval works were subjected to rethinking. The metaphor of the body politic became a constant leitmotif of the 14th century mirrors for princes, who with the help of that trope tried to explain the complex social structure and reflect on the abstract nature of the state. While in them the political body often served as an ideal, a model of correct state structure, the antipode became the image of a sick or monstrous body. Eustache Deschamps refers to such an image in his ballads, using it to demonstrate the deplorable state of the French kingdom, mired in feuds and the hardships of war with England. The metaphor of the political body was interpreted in a variety of ways: it was a concept designed to consolidate opposing social groups and political factions around the figure of the monarch, but at the same time it could be used to criticize the corruption of the ruler’s close associates. Such different strategies of interpretation of that concept compel to further analyze the genesis and development of metaphorical descriptions of the state.

A reexamination of the offices of Three Excellencies in the final years of the Western Han, and Four Advisers under Wang Mang’s Xin Dynasty

<p>秦至西漢本以丞相為宰相，到東漢演變成地位相等的三公並列宰相。西漢晚期至新朝是從獨相制變化為多相制的關鍵時期，本文旨在釐清三公官制成立的過程。西漢晚期的兩次三公官改制，目標是以中朝的大司馬與外朝的丞相、御史大夫並列宰相。將大司馬改造成和外朝的丞相具有相同職能的職官，是三公官改制的關鍵。大司馬本來是一個頭銜，由輔政的將軍兼任，沒有印綬、官屬。經歷兩次改制後，大司馬獲得印綬、官屬，得到宰相的辦事機構及監督百官執行權，也要承擔調和陰陽、安輯百姓的責任。在選任上，大司馬本來常以任近侍官的外戚擔任，選任丞相、御史大夫則重視循序漸進的任官資歷。改制後，過去任官資歷足以擔任丞相的一般官吏也能任大司馬。儘管大司馬經過兩次改制逐漸「外朝化」，它始終未失去在宮中「領尚書事」輔政的權力，與另外二公並非同質的職官。直到王莽建立新朝時，大司馬才失去輔政權，完成外朝化，三公也確立分職，改制遂告完成。不過三公官似乎不能滿足王莽對宰輔的想像，他以古制為基礎，另設高於三公的四輔。四輔不但與三公一起管理全國政事，也在宮中輔政，為兼攬內、外的宰相。東漢僅繼承三公官，兼治內外的四輔則未被採用。</p> <p> </p><p>In the periods of Qin and Western Han dynasties, Imperial Chancellors (chengxiang 丞相) served as chief aides to the emperor – zaixiang (宰相), a role later ceded to the Three Excellencies (san gong 三公) by the time of the Eastern Han. Between the end of the Western Han, and the establishment of the Xin Dynasty, a pivotal change occurred in the role of the chief aide – it went from being held by a single chancellor, to a collective function. This study aims to expound the formation of the latter, embodied in the system of Three Excellencies. The nature of the Three Excellencies was reformed twice in the final years of the Western Han, with the aim of endowing the Marshal of State (dasima 大司馬) in the Inner Court alongside the Imperial Chancellor (chengxiang 丞相) and the Imperial Counsellor (yushi dafu 御史大夫) of the Outer Court with the function of zaixiang. A key change in the process of reforming the system of Three Excellencies was making the functions of Marshal of State identical to those of Imperial Chancellor. Marshal of State was originally an official title given to generals tasked with assisting the ruler, but individuals holding it were not given imperial seals, or subordinate bureaucrats. After two reforms, Marshals of State received imperial seals, and subordinates, and were given administrative, and supervisory powers of zaixiang, as well as tasked with maintaining a cosmic balance, and peace among the populace. Originally, the individuals selected for the position of Marshal of State were often distaff relatives of personal imperial attendants, while those tapped for positions of Imperial Chancellor, and Imperial Counsellor were qualified public officials advancing through the ranks. After reforms, officials qualified to hold the post of Imperial Chancellor could also become Marshals of State. Although the responsibilities of Marshal of State have gradually moved from the Inner to the Outer Court following the two reforms, this position never entirely lost its ‘internal’ prerogatives of the Manager of the Affairs of the Masters of Writing (ling shangshushi 領尚書事), which set it apart from the other two Excellencies. Only with the establishment of Xin Dynasty by Wang Mang did the Marshals of the State lose their function of assisting the ruler, and their prerogatives were moved entirely to the Outer Court, which coincided with a clear separation of responsibilities between the Three Excellencies. The process of systemic reform was thus complete. However, the Three Excellencies did not seem to fulfill Wang Mang’s expectations for chief aides. The new emperor based the mode of his rule on ancient examples, and established the offices of Four Advisers (sifu 四輔), superior to the Three Excellencies. The new group held the reins of state administration alongside the Three Excellencies, on top of assisting the emperor as zaixiang, thus combining Inner, and Outer Court functions. The ensuing Eastern Han Dynasty continued the appointment of the Three Excellencies, but abandoned the combined internal-external office of Four Advisers.</p> <p> </p>

Aural myiasis in Ancient Rome: Celsus and the ear maggots.

Although today there is extensive scientific literature on aural myiasis, a historical study of the subject has yet to appear. This short article reports the first description of aural myiasis in the Western medical literature. Methods involved: (1) scholarship review of ear diseases within Ancient Greek and Roman medical texts (L'Année philologique); (2) linguistic analysis for text identification through the Library of Latin Texts, the Thesaurus Linguae Latinae and the Loeb Classical Library; and (3) translation of the Latin texts that described cases of aural myiasis with commentary. To our knowledge, the earliest case of aural myiasis in Latin medical literature is reported by the Roman encyclopaedist Celsus (first century CE). In his De Medicina, he describes cases of Wohlfahrtia magnifica maggot infestation of the ear and how to treat affected patients. Despite present advances in otology, we believe that much insight can still be gained from this ancient example of medical history in ear diseases. A more comparative analysis of the subject is to be considered in the future, which will provide more data from different cultures and times.