Alberto C. Riccardi

Research advances in the Mesozoic tectonic regimes during the formation of Jiaodong ore cluster area

Based on research advances of the tectonic regime in Jiaodong ore cluster area and the related tectonic regime transformation in Mesozoic era in the eastern region of North China, in this paper, we first summarize some key problems required to be studied further on. Then we suggest an approach to dealing with these problems. It is known that the gold deposits in Jiaodong ore cluster area, which are of different mineralization styles, spatial distributions and geological settings, might be as a result from one or more geologic events in Mesozoic. Till now, this kind of research on the temporal evolution and spatial migration sequence, especially on the geodynamic mechanism of the above events, is far from sufficient. Moreover, quantitatively describing the action mode and the temporal-spatial framework of tectonic dynamic regimes and formulating the relative contribution of every tectonic dynamic regime for the metallogensis are still challenges to the geologists studying on the formation of Jiaodong ore cluster area. According to the interpretation of the regional tectonic analysis, the structural dynamics, the observation and the exploration of the mineralization network, we propose a geological-physical-chemical model with some constraints originated from the comprehensive analysis. We then use this model to simulate the coupled processes of the structural deformation, thermal transport, fluid flow and the chemical reaction. The obtained results indicate that the model is efficient in further analyzing the temporal-spatial evolutional trail of the tectonic regime in Jiaodong ore cluster area and in further understanding the nature of the mass metallogensis.

Albian heteromorph ammonoids from southern Patagonia, Argentina

We have been processing organic-rich shale from the Carboniferous Luocheng Formation, Peoples Republic of China, for microcrinoids and microgastropods. Initial attempts to disaggregate the shale using standard techniques (e.g., chlorine bleach, Quaternary-O, paint thinner, Stoddards solution) proved futile. Nothing worked on the mixed organic/clay matrix in which the fossils were entombed. One particularly frustrating evening, a television commercial, in which a large hair clog in a clear plastic drain pipe was dissolved, inspired us to purchase and try some drain cleaner for processing our samples. After reading numerous drain-cleaner labels, we selected Liquid-plumr® because it contained one of the strongest concentrations of sodium hypochlorite and sodium hydroxide easily available. We are not necessarily recommending Liquid-plumr® over other brands; however, some drain cleaners are nothing more than concentrated sulfuric acid, so careful scrutiny of the labels is recommended.

Remarks on the Tithonian-Berriasian ammonite biostratigraphy of west central Argentina

The bromalite record of the western United States is quite limited, especially in contrast to the Triassic and Cretaceous records of the same region. Indeed, there are only a handful of well documented vertebrate bromalites from the Jurassic strata of the western USA, including: (1) coprolites from the nonmarine Early Jurassic Glen Canyon Group; (2) consumulites and evisceralites from the Middle Jurassic Todilto and Sundance formations; and (3) consumulites, putative coprolites and pseudobromalites from the nonmarine Upper Jurassic Morrison Formation. Early Jurassic red beds are notably less fossiliferous than those of the Triassic (e.g., contrast the fossil record of the Chinle and Glen Canyon groups). The Middle Jurassic of the region includes several eolianites and sabkha-like deposits representing environments that preserve few bromalites. The Upper Jurassic Morrison Formation contains abundant vertebrate body fossils and many tracks but very few bromalites in contrast to many broadly similar fluvial deposits of Triassic and Cretaceous age in the same region. The global bromalite record also appears to be depauperate in the Jurassic, with a few exceptions such as marine shales and lithographic limestones in Europe (e.g., Lower Jurassic of England, Upper Jurassic Solnhofen Limestone of Bavaria). This relative lack of a global Jurassic bromalite record may in part be more a result of a lack of collection and study. However, the relative lack of nonmarine bromalites is clearly influenced by high sea levels in the Early Jurassic, a paucity of Middle Jurassic nonmarine vertebrate-bearing units and a lack, or lack of recognition of, bromalites in major Upper Jurassic nonmarine vertebrate faunas (e.g., China, Tanzania, Portugal, etc.). In the Western United States there is clearly a need for more detailed examination of known specimens (e.g., putative Morrison coprolites) and a focus on collecting more examples. 1 Flying Heritage Collection, 3407 109thSt SW, Everett, WA 98204; e-mail: adrianhu@flyingheritage.com 2 New Mexico Museum of Natural History and Science, 1801 Mountain Road NW, Albuquerque, NM 87104; e-mail: spencer.lucas@state.nm.us JURASSIC BROMALITES IN THE WESTERN UNITED STATESThe Springdale Sandstone records a large number of reversals of the geomagnetic field. Forty-three percent of the 60 m section investigated showed 25 polarity intervals. These frequent reversals follow the nearly constant normal polarity of the underlying Whitmore Point strata. Comparison of the reversal sequence of the Springdale Sandstone with a core from the Paris Basin suggests that the Springdale Sandstone spans an interval extending possibly from as early as late Hettangian to early-mid Sinemurian time. The paleomagnetic pole calculated from Springdale paleomagnetic directions is statistically identical to that of the underlying Whitmore Point Member of the Moenave Formation, and considerably different from that of the overlying Kayenta Formation. This similarity suggests that the Springdale Sandstone should be retained as a member of the Moenave Formation, not considered part of the Kayenta Formation.Two partial skeletons of allosaurid theropods belonging to an adult and a juvenile from the Upper Jurassic (Tithonian) Morrison Formation of McElmo Canyon in Montezuma County, southwestern Colorado, were discovered in 1953 by the late Joseph T. Gregory and David Techter. The adult specimen consists of several isolated cranial and postcranial skeletal elements that are exceptionally well-preserved and include the left premaxilla, maxilla, dentary, teeth, quadratojugal, two caudal vertebrae, pubic peduncle, ischium, proximal tibia, a nearly complete left foot, and several isolated teeth, whereas the juvenile specimen is represented by the distal portion of the right dentary and a fragmentary splenial. The specimens represent a new species of Allosaurus , here named Allosaurus lucasi , which differs from Allosaurus fragilis by having a relatively short premaxilla and robust quadratojugal with short jugal process and a short quadrate process of the quadratojugal that is at the same level as the rostral quadratojugal ramus. The presence of a new species of Allosaurus in the Tithonian of North America provides further evidence of the taxonomic and morphological diversity of the Allosauridae clade and their continuous evolutionary success, which extended to the Cretaceous.To evaluate the utility of high-resolution micro-computed tomography (micro-CT) in observing radiolarian fossils, we examined the skeleton of the Jurassic radiolarian fossil Protunuma ? ochiensis Matsuoka using a micro-CT device. Although this species is a closed Nassellarian with a thick exterior wall, important taxonomic characters on the interior and exterior of the shell were represented almost perfectly in the acquired three-dimensional computer graphic images. These characters include those documented in the original description, such as the height and width of the skeleton, the outline, the number of segments, the pore arrangement and other features. In addition, the structure of the initial spicule of this species was revealed newly. An enlarged plaster radiolarian model printed using the laminated modelling method was useful for detailed observation. Nondestructive omnidirectional observation is an advantage of this method, which is not possible with scanning electron microscopy or optical microscopic investigations. Micro-CT technology would become an effective observational tool for radiolarian studies in the near future. method of visualising and measuring the internal geometries of opaque objects. Micro-CT is specialised for visualising the structures of micrometreto centimetre-sized objects with greatly increased resolution. This developing technoloINTRODUCTION X-ray computed tomography (CT), which is commonly used for medical and industrial purposes, is a nondestructive 1 Gas Hydrate Research Laboratory, Meiji University, Kanda-Surugadai 1-1, Chiyoda-ku, Tokyo, 101-8301, Japan; phone and fax: +81-3-3296-4582; e-mail: nao.ishida21@mbn.nifty.com. 2 Department of Mechanical Engineering, Faculty of Science and Engineering, Setsunan University, Neyagawa 572-8508, Japan; phone: +81-72-839-9165; e-mail: kishimoto@mec.setsunan.ac.jp. 3 Department of Geology, Faculty of Science, Niigata University, Niigata 950-2181, Japan; phone and fax: +81-25-262-6376; e-mail: amatsuoka@geo.sc.niigata-u.ac.jp. 4 Research and Development Center for Global Change (RCGC), JAMSTEC, Yokosuka, Kanagawa 237-0061, Japan; phone: +81-46-867-9436; e-mail: kimopy@jamstec.go.jp. 5 Graduate School of Science and Technology, Niigata University, Niigata 950-2181, Japan; phone and fax: +81-25-262-7640; e-mail: kurihara@geo.sc.niigata-u.ac.jp. 6 Department of Mechanical Engineering, Faculty of Science and Engineering, Toyo University, Kawagoe, Saitama 350-8585, Japan; phone: +81-49-239-1396; e-mail: tyoshino@toyo.jp. 78 Naoto Ishida et al. gy is being applied to a wide range of geological and palaeontological investigations (e.g. Ketcham, Carlson, 2001). To evaluate the potential of micro-CT imaging technology in investigating microfossils, the authors have experimentally examined the skeletons of foraminifers, ostracodes, diatoms and radiolarians. For example, Matsuoka et al. (2012) reported the exact pore number of a specimen of the genus Pantanellium and represented its pore distribution on a spherical shell based on three-dimensional (3D) scanning data. Furthermore, Yoshino et al. (2014) presented a method that uses 3D information to automatically determine the pore numbers of spherical radiolarian skeletons. In this study, we present the results of 3D scanning of the Jurassic radiolarian Protunuma ? ochiensis Matsuoka using a high-resolution micro-CT scanner. Although closed Nassellarians, including this species, are commonly recovered from Jurassic sediments, conventional methods cannot be used for nondestructive observation of a combination of both their surface textures and their internal structures. Observation using high-resolution micro-CT overcomes this difficulty. This study introduces the observation of radiolarian fossils using 3D imaging methods and emphasises the utility of high-resolution micro-CT for palaeontological investigations. METHODS AND MATERIALSThe thick and relatively complete Jurassic succession of eastern Greenland provides a unique biostratigraphic record for the North Atlantic region. The main biostratigraphic control for the succession has been provided by molluscs, especially ammonites and to a lesser extent by bivalves and belemnites. The late John Callomon and colleagues recognised 93 Boreal ammonite-bearing horizons in the Mid to Late Jurassic. This provides a reliable backbone to the biostratigraphy of these strata, prompting a palynological colleague to comment that they are the “Policemen of Jurassic Stratigraphy”. Other biostratigraphically significant microfossil and palynological groups, can be calibrated against this standard, but on their own cannot achieve the same precision.​ The Early Jurassic of eastern Greenland does not have such fine control as later parts of the period. No single biostratigraphic group can be used successfully throughout the interval, and there are only three significant ammonite faunas during this period. Reliance on various different organisms is necessary to cope with the changing range of marine to non-marine environments. CASP field-work from 1990 to 2012 has resulted in the collection of much biostratigraphic material. In this article, published data are summarised together with previously unpublished data in the form of a unified table. The integrated chart shows detailed columns for the whole eastern Greenland Jurassic. It demonstrates the ammonite, palynological and microfossil events/biozones and horizons which are correlated by time. More limited information is available on belemnites, bivalves and macroflora. This is the first time such an integrated biostratigraphic scheme has been assembled for the Jurassic of eastern Greenland. It will be of value to the offshore oil-industry in the northern North Atlantic and on the Barents Shelf as well as to field geologists in Greenland.Measured sections of Jurassic San Rafael Group strata correlated by lithostratigraphy along an ~60 km transect between Bluff and the Abajo Mountains in southeastern Utah indicate that: (1) the Carmel Formation is continuous and disconformable on the Navajo Sandstone (J-2 unconformity); (2) the Entrada Sandstone (Slick Rock Member) is continuous and conformable on the Carmel; (3) the Summerville Formation is continuous and does not intertongue with the Entrada (its base is the J-2 unconformity); (4) the Bluff Sandstone grades northward into the upper Summerville south of the Abajo Mountains; (5) the Recapture Member of the Bluff is physically continuous with at least part of the Tidwell Member of the Summerville; and (5) the base of the Salt Wash Member of the Morrison Fm. is a pervasive unconformity (J-5) with demonstrable local stratigraphic relief of up to 14 m. These observations counter previous claims of extensive Entrada-Summerville intertonguing in southeastern Utah and do not support recognition of depositional sequence boundaries in the Entrada and Summerville lithosomes. Though Entrada deposition may have been by a wet eolian system, its southeastern Utah outcrops are well to the south/ southeast of any marine and paralic facies with which the Entrada intertongues. 1 New Mexico Museum of Natural History, 1801 Mountain Road NW, Albuquerque, NM 87104 USA; e-mail: spencer.lucas@state.nm.us fornia and left eolian sandstone up to 660 m thick called in different regions Navajo Sandstone, Nugget Sandstone or Aztec Sandstone. Later, during the Middle Jurassic (Callovian), the Entrada erg extended from Utah to Oklahoma and from New Mexico to Wyoming. The last Jurassic erg, the Bluff sand sea, accumulated during the Middle-Late Jurassic transition and was primarily located in the Four Corners. The two younger ergs – Entrada and Bluff – accumulated at a time when a Jurassic Cordilleran seaway was present to the northwest, in what is now Idaho and parts of northern and western Utah. The ergs were landward of that seaway and their deposits interfinger to the northwest with its marine and paralic facies. In southeastern Utah, O’Sullivan (1980) INTRODUCTION Jurassic strata of the American Southwest include some of the most intensively studied eolian strata on the planet. These strata document several extensive sand seas (ergs) of Jurassic age that covered many thousands of square kilometers, including the largest of all Phanerozoic ergs, the Navajo erg (e.g., Kocurek, Dott, 1983; Blakey et al., 1988). The Jurassic erg history in the southwestern USA begins with the Wingate erg, which covered the Four Corners during the Triassic-Jurassic boundary interval. Next youngest is the Navajo erg, which extended at least from Wyoming to Cali-

Jurassic belemnite distribution patterns: implications of new data from Antarctica and Argentina

Belemnites are nektopelagic cephalopods which developed a widespread pattern of distribution in the Jurassic, and most authors have accepted that their centre of origin was Europe. Available data suggest that the belemnites developed a global distribution only in the Toarcian, some 15 Ma after their first appearence in the European Hettangian. Development of the Boreal and Tethyan belemnite realms took place in the Middle Jurassic and continued through to the Cretaceous. New data from Argentina and the Antarctic Peninsula reaffirms the development of the global distribution of belemnites in the Toarcian, and sheds new light on the biogeographical patterns for the Jurassic of the southern hemisphere. This has considerable implications for understanding the development of faunal realms in the Mesozoic.

A new U–Pb zircon age for an ash layer at the Bathonian–Callovian boundary, Argentina

A U–Pb zircon age of 164.64 ± 0.2 Ma (95% confidence level) is reported for an ash bed, at the Bathonian–Callovian (late Middle Jurassic) boundary, determined by isotope dilution thermal ionisation mass spectrometry from individual, chemically abraded grains. The volcanic ash layer occurs within the Chacay Melehue Formation, Chacay Melehue section, Neuquén Province, central west Argentina, above the last record of ammonites of the regional Lilloettia steinmanni Standard Zone, and, stratigraphically, where the first of those of the regional Eurycephalites vergarensis Standard Zone appears, generally referred to as the uppermost Bathonian and the lowermost Callovian, respectively. This ash layer represents the only known datable horizon worldwide that is directly related to a well-documented ammonite faunal succession at this boundary. The U–Pb zircon age is older than one previously reported for the same bed and closer to an estimation of 164.7 ± 4 Ma for the boundary based on the scaling durations of ammonite zones to their subzones in the sub-boreal standard zonation. The new age agrees better with the age model for the Oxfordian through Bathonian M-sequence magnetic anomalies in the Pacific and contributes to the radioisotopic age calibration of the Jurassic time scale.

CISURALIAN CEPHALOPODS FROM PATAGONIA, ARGENTINA

Abstract Upper Paleozoic Cephalopoda of west-central Patagonia are revised, based on reexamination of all available specimens and of most localities in Chubut Province, Argentina. Nautiloidea Orthocerida are represented by Sueroceras irregulare Riccardi and Sabattini, S.? chubutense (Closs), Sueroceras sp., and Mooreoceras zalazarense Sabattini and Riccardi and Pseudorthoceratidae gen. and sp. indeterminate; Nautilida by Amosiceras reticulatum new genus and species; and Ammonoidea Goniatitida by Glaphyrites taboadai new species and Glaphyrites sp. This fauna belongs to the Cisuralian Sueroceras irregulare and Mooreoceras zalazarense assemblage zones.

Geographical and geological explorations of the La Plata Museum 1884–1905

Abstract The contributions of the La Plata Museum to the geology of Argentina began following the exploratory trips of its founder, F.P. Moreno, in the 1870s. The geological expeditions of the La Plata Museum started in the 1880s and covered the Andean region, although they were focused in the Patagonian Andes. They became more important from 1893 when they were related to explorations aimed at fixing the boundary between Argentina and Chile. Within 10 years the geographical and geological bases of large and almost unknown regions were established. R. Hauthal studied the area between the Last Hope Inlet and Lake Belgrano, defining its stratigraphy and publishing the first geological map of the Cordilleran region between c. 49° 30′ and 52° S. The geology between Lake Buenos Aires and the Rio Negro (41–47° S) was established by Santiago Roth. The stratigraphic succession, facies and structural changes through the Argentine–Chilean Cordillera at the latitude of Lake Nahuel Huapi and Lake Lacar were studied by L. Wehrli, while studies at the latitude of Neuquén and Mendoza (36–39° S) were carried out by C. Burckhardt. Mesozoic and Cenozoic fossils were studied either in the Museum or abroad. Supplementary material: Map of southern South America (Argentina and Chile) showing the distribution of towns in 1870 is available at https://doi.org/10.6084/m9.figshare.c.3283385.v1

Life and geological studies of Joaquín Frenguelli

Abstract Joaquín Frenguelli was born in Rome, Italy in 1883 and died in Santa Fe, Argentina in 1958. After receiving his PhD in medicine from Rome University, he moved to Argentina in 1911 and worked as a medical doctor in the cities of Santa Fe and Córdoba until 1929. From 1920 until 1933 he was a professor of geology at the Littoral National University. In 1934 he moved to La Plata, where he was director of the Museum of Natural Sciences (1935–46). The scientific work of Frenguelli is characterized by its scope and excellence and its main focus was on the Late Cenozoic. Frenguelli modified the chronology of the stratigraphic scheme of the Pampas region, proposed a relationship with climatic episodes and then expanded it, directly or indirectly, to the whole record of the Late Cenozoic in Argentina. His contributions on diatoms and other microscopic organic remains, as well as on fossil vertebrates and invertebrates, were related to the environmental setting of the Late Cenozoic. In the 1940s, Frenguelli also worked on the fossil plants of the continental Upper Palaeozoic and Early Mesozoic rocks of Argentina. As a result, he characterized the Triassic successions, introducing new stratigraphic units and discussing their relationships and chronology.

Tuberosciponoceras: a new dimorphic ammonoid genus from the Upper Albian of Patagonia, Argentina

Tuberosciponoceras insolitum n. gen., n. sp. is a single dimorphic species in the Upper Albian of the Austrat Basin, southern Patagonia. The short-lived genus was characterized by distinct ventral tubercles on all ribs and a deep, trifid internal lobe.KurzfassungTuberosciponoceras insolitum n. gen., n. sp. ist eine dimorphe Art aus dem Oberen Albium des Austraten Beckens in Südpatagonien. Die kurzlebige Gattung ist durch seitliche ventrale Tuberkeln auf allen Rippen und einen tiefen, trifiden Internlobus gekennzeichnet.

The Albian ammonite Aioloceras Whitehouse in Antarctica

The first record of the Albian ammonite Aioloceras is documented from the Kotick Point Formation, James Ross Island, northern Antarctic Peninsula. The material is identified with the type species, Aioloceras argentinum (Bonarelli, 1921), previously only known from southern Patagonia. It is associated with Desmoceras sp., Anagaudryceras sp., Parasilesites sp., Rossalites sp. and Phyllopachyceras sp. On the basis of this assemblage, the presence of the Aioloceras argentinum Assemblage Zone from Patagonia, which is considered coeval to the upper lower Albian Mammillatum Superzone, is extended to Antarctica.