Radiolarian biochronology and Pacific origin of Jurassic-Cretaceous oceanic terranes in Costa Rica and Puerto Rico

AbstractAs demonstrated during several recent geological conferences, there is still a large debate concerning the origins of the Mesozoic oceanic remnants on the Caribbean Plate. The geodynamic models describing the Mesozoic history of the Caribbean realm can be divided into two main categories based on the origin of the Caribbean Plate: 1) An in situ origin between the Americas; 2) A Pacific origin and an eastward transport relative to the Americas. The study of the ribbon-bedded radiolarite is a key in determining the origins of associated Mesozoic oceanic terranes and may help to achieve a general agreement regarding the basic principles on the evolution of the Caribbean Plate. The Early Jurassic to early Late Cretaceous Bermeja Complex of Puerto Rico, witch contains serpentinized peridotite, altered basalt, amphibolite, and chert (Mariquita Chert Formation), and the contemporaneous Santa Rosa Accretionary Complex, which crops out in several half-windows along the south shores of the Santa Elena Peninsula in northwestern Costa Rica, are two of these little-known and crucial ophiolitic mélanges. The Manzanillo and Matambú fore-arc Terranes of the Nicoya Peninsula in the northwestern Costa Rica, which contain Late Cretaceous to Early Paleogene radiolarian-bearing siliceous mudstones and cherts associated with arc-derived mafic to intermediate volcaniclastics, bring important information on the history of the western active margin of the Caribbean Plate. A systematic radiolarian study of these three regions is presented herein in three different articles.The radiolarian biochronology of the Mariquita Chert Formation of the Bermeja Complex presented in this work indicate an early Middle Jurassic to early Late Cretaceous (late Bajocian-early Callovian to middle Albian-middle Cenomanian) age for the Mariquita Chert Formation. The illustrated assemblages contain 150 species, of which 3 are new (Pantanellium karinae, Loopus bermejaense, and L. boricus), and belonging to 59 genera. A review of the previous radiolarian published works on this formation and the results of this study suggest that the Bermeja Complex ranges in age from Middle Jurassic to early Late Cretaceous (late Aalenian to middle Cenomanian) and also reveal a possible feature of the complex, which is the youngling of radiolarian cherts from north to south, evoking a polarity of accretion. On the basis of a currently exhaustive inventory of the ribbonbedded radiolaritic facies on the Caribbean Plate, a re-examination of the distribution of Middle Jurassic sediments associated with oceanic crust from the Caribbean realm, and a paleoceanographical argumentation on the water currents, we come to the conclusion that the radiolarite and associated Mesozoic oceanic terranes of the Caribbean Plate are of Pacific origin. The previous argument for a Pacific origin of the Bermeja Complex presented by Montgomery et al. (1994a), based on their radiolarian age and their estimation of the oldest Proto-Caribbean oceanic crust, is nowadays seriously questionable, owing to the recent progresses in radiolarian biostratigraphy and new discoveries on the age of the first oceanic crust spreading between the Americas. Furthermore, we interpret the radiolarian Parvicingulidae-rich assemblages in the low-latitude Caribbean context as potential indicators of upwelling or land nutrients inputs, instead of indicators of paleolatitudes,as firstly stated by Pessagno and Blome (1986). Eventually, a discussion on the origin of the cherts of the Mariquita Formation illustrated by Middle Jurassic to middle Cretaceous geodynamic models of the Pacific and Caribbean realms bring up the possibility that the rocks of the Bermeja Complex are remnants of two different oceans.The Santa Rosa Accretionary Complex contains various oceanic assemblages of alkaline basalt, radiolarite and polymictic breccias. The radiolarian biochronology (19 illustrated assemblages, 232 species belonging to 63 genera) presented in this work indicate an Early Jurassic to early Late Cretaceous (early Pliensbachian to earliest Turonian) age for the sediments associated with oceanic basalts or recovered from blocks in breccias or megabreccias from the Santa Rosa Accretionary Complex. This study brings to light the Early Jurassic age of a sequence of ribbon-bedded radiolarite, which was previously thought to be of Cretaceous age, intruded by alkaline basalts sills. The presence of Early Jurassic large reworked blocks of radiolarite in a polymictic megabreccia, firstly reported by De Wever et al. (1985) is confirmed. Therefore, the alkaline basalt associated with these radiolarites could be of Jurassic age. In the Carrizal tectonic window, Middle Jurassic radiolarian chert blocks and Early Cretaceous brick-red ribbon-bedded radiolarites overlying pillow basalts are interpreted as fragments of a Middle Jurassic oceanic basement accreted to an Early Cretaceous oceanic plate, in an intra-oceanic subduction context. Whereas, knobby radiolarites and black shale at Playa Carrizal are indicative of a shallower middle Cretaceous paleoenvironment. Other younger oceanic remnants documented the rapid approach of the site of sedimentation to a subduction trench during the late Early Cretaceous (AlbianCenomanian), maybe early Late Cretaceous (Turonian).In total, 60 species belonging to 34 genera were present in relatively well-preserved radiolarian faunas from volcaniclastics and associated pelagic and hemipelagic rocks of the Matambú and Manzanillo terranes, ranging in age from Late Cretaceous to Early Paleogene (middle Turonian-Santonian to late Thanetian-Ypresian). This study shows that radiolarians can provide significant biostratigraphic control in the Nicoya Peninsula where very similar lithologies of different ages are present. Two radiolarian samples directly date the Berrugate Formation for the first time (middle Turonian-Santonian and Coniacian-Santonian). These ages allow to determine a volcanic arc activity on the western edge of the future Caribbean Plate at least since the Santonian that could have lasted through the middle Turonian-early Campanian interval by stratigraphic superposition. Moreover on the basis of these radiolarian ages, the Loma Chumico Formation of Albian age, and the Berrugate Formation of middle Turonian-early Maastrichtian age, can now be clearly differentiated. Two samples from the Sabana Grande Formation give a Coniacian-Santonian age and a Coniacian-Campanian age and indicate that there is a stratigraphic gap of ~10 million years between this formation and the underlying Albian Loma Chumico Formation.RésuméComme cela a pu se vérifier à plusieurs reprises lors de conférences géologiques récentes, le débat sur l'origine des terrains océaniques mésozoïques de la Plaque Caraïbes est toujours d'actualité. Les modèles géodynamiques décrivant l'histoire de la région caraïbes peuvent être classés en deux catégories basées sur l'origine de la Plaque Caraïbes : 1) Une origine in situ entre les Amériques ; 2) Une origine Pacifique et un transport vers l'est, par rapport aux Amériques. L'étude des radiolarites rubanées est capitale pour la détermination de l'origine des terrains océaniques allochtones du Mésozoïque et peut être utile pour parvenir à un compromis général concernant les principes basiques de l'évolution de la Plaque Caraïbes. Le complexe de Bermeja à Porto Rico qui est constitué de péridotites serpentinisées, de basaltes altérés, d'amphibolites et de cherts (Formation des Cherts de Mariquita), et le Complexe d'Accrétion de Santa Rosa qui affleure dans plusieurs demi-fenêtres tectoniques au sud de la Péninsule de Santa Elena au nord-ouest du Costa Rica sont deux de ces mélanges ophiolitiques peu décrits et déterminants. Les terrains de fore-arc de Manzanillo et de Matambu dans la Péninsule de Nicoya au nord-ouest du Costa Rica qui sont composés de calcaires siliceux et de cherts riches en radiolaires associés à du matériel volcanique d'arc mafique à intermédiaire, apportent d'importantes informations sur l'histoire de la marge active occidentale de la Plaque Caraïbe. Une étude systématique des radiolaires de ces trois régions est présentée dans ce travail sous forme de trois articles.La biochronologie des radiolaires de la Formation des Cherts de Mariquita du Complexe d'Accrétion de Santa Rosa présentée dans ce travail indique un âge Jurassique Moyen inférieur à Crétacé Supérieur inférieur (Bajocien supérieur-Callovien inférieur à Albien moyen-Cénomanien moyen) pour la Formation des Cherts de Mariquita. Les assemblages illustrés contiennent 150 espèces, parmis lesquelles 3 sont nouvelles (Pantanellium karinae, Loopus bermejaense et L. boricus), et appartenant à 59 genres différents. Une révision des travaux publiés précédemment sur les radiolaires de cette formation, ainsi que les résultats de cette étude suggèrent que le Complexe de Bermeja a un âge allant du Jurassique moyen au Crétacé Supérieur inférieur (Aalénien supérieur à Cénomanien moyen) et révèle aussi une caractéristique éventuelle du complexe qui est le rajeunissement des radiolarites du nord au sud, évoquant une polarité d'accrétion. Sur la base d'un inventaire actuellement exhaustif du facies radiolaritique rubané sur la Plaque Caraïbes, d'un nouvel examen de la distribution globale des sédiments du Jurassique Moyen associés à de la croûte océanique et d'une argumentation paléocéanographique sur les courants, nous arrivons à la conclusion que les radiolarites et les unités tectoniques océaniques du Mésozoïque associées de la Plaque Caraïbes sont d'origine pacifique. L'argument antérieur pour une origine pacifique du Complexe de Bermeja présenté par Montgomery et al. (1994a), basé sur leur âge à radiolaire et leur estimation de l'âge de la plus vieille croûte océanique des Proto-Caraïbes, est sérieusement remis en question aujourd'hui, en raison des progrès récents de la biostratigraphie des radiolaires et des nouvelles découvertes concernant l'âge du début de l'océanisation entre les Amériques. En outre, dans le contexte de basses latitudes des Caraïbes, nous interprétons les assemblages à radiolaires riches en Parvicingulidae comme étant des indicateurs potentiels d'apports en nutriments des zones d'uppwelling ou des terres, plutôt que des indicateurs de paléolatitudes, comme exposer pour la première fois par Pessagno et Blome (1986). Finalement, une discussion sur l'origine des cherts de la Formation de Mariquita illustrée par des modèles géodynamiques du Jurassique Moyen au Crétacé moyen des régions pacifique et caraïbes, fait poindre la possibilité que les roches du Complexe de Bermeja proviennent de deux océans différents.Le Complexe d'Accrétion de Santa Rosa contient plusieurs assemblages océaniques différents de basaltes alcalins, radiolarites et brèches polymictes. La biochronologie des radiolaires (19 assemblages illustrés, 232 espèces appartenant à 63 genres) présentée dans ce second travail indique un âge Jurassique Inférieur à Crétacé Supérieur inférieur (Pliensbachien inférieur à Turonien initial) pour les sédiments associés aux basaltes océaniques ou provenant de blocs dans des brèches ou des mégabrèches du Complexe d'Accrétion de Santa Rosa. Cette étude met en évidence l'âge Jurassique Inférieur d'une séquence de radiolarites rubanées entrecoupée de sills de basaltes alcalins, dont l'âge estimé était précédemment le Crétacé.La présence de blocs plurimétriques de radiolarites d'âge Jurassique Inférieur remaniés dans une mégabrèche polymicte, dont la présence avait été signalée par De Wever et al. (1985), est confirmée. Par conséquent, les basaltes alcalins associés à ces radiolarites pourraient aussi être d'âge Jurassique. Dans la fenêtre tectonique de Carrizal, des blocs de radiolarites d'âge Jurassique Moyen et des radiolarites du Crétacé Inférieur recouvrant des basaltes en coussins sont interprétés comme des fragments d'une croûte océanique d'âge Jurassique Moyen accrétés à une plaque océanique d'âge Crétacé Inférieur, dans un contexte de subduction intra-océanique. Alors que dans la même zone, les radiolarites « noueuses » et les argiles noires associées sont interprétées comme des indicateurs d'un milieu peu profond au Crétacé. D'autres fragments océaniques plus jeunes documentent une approche rapide du lieu de sédimentation vers une fosse de subduction pendant le Crétacé Inférieur supérieur (Albien-Cénomanien), peut-être Crétacé Supérieur (Turonien).Au total, 60 espèces appartenant à 34 genres ont été déterminées à partir de faunes à radiolaires relativement bien préservées, extraites de roches volcanoclastiques et pélagiques à hémipélagiques associées, provenant des terrains de Matambu et Manzanillo et ayant des âges compris entre le Crétacé Supérieur et le Paléogène Inférieur (Turonien moyen-Santonien à Thanétien supérieur-Yprésien). Cette étude montre que les radiolaires peuvent fournir un contrôle stratigraphique significatif dans la Péninsule de Nicoya, où des lithologies similaires, mais d'âges différents sont présentes. Deux échantillons à radiolaires permettent de dater la Formation de Berrugate pour la première fois (Turonien moyen-Santonien et Coniacien-Santonien). Ces âges permettent d'établir une activité volcanique d'arc le long de la marge occidentale de la futur Plaque Caraïbes au moins depuis le Santonien et qui pourrait avoir durée jusqu'au Turonien moyen-Campanien inférieur. De plus, sur la base de ces âges à radiolaires, la Formation de Loma Chumico d'âge Albien, et la Formation de Berrugate d'âge Turonien moyen-Maastrichtien inférieur, peuvent maintenant être différenciées. Deux échantillons de la Formation de Sabana Grande donnent des âges Coniacien-Santonien et Coniacien-Campanien et indiquent qu'il existe une lacune stratigraphique d'environ 10 millions d'années entre cette formation et la Formation de Loma Chumico sous-jacente d'âge Albien.

A comunicação eletrônica e a alteração de tempo e espaço na produção do conhecimento científico

Versa sobre a influência da comunicação eletrônica na produção do conhecimento científico na área de física da Universidade Estadual de Campinas entre o início das décadas de 1980, 1990 e 2000. Verifica se o acesso mais abrangente e rápido à informação científica proporcionado pelos periódicos eletrônicos e seus estoques ou portais tem ocasionado modificações no sujeito cognoscente. Por meio da correlação entre dados de dissertações/teses e dados retirados de suas referências bibliográficas (títulos de periódicos citados e anos de publicação), conclui-se que os pesquisadores estão citando mais títulos de periódicos e mais rapidamente, talvez por conta do fenômeno da comunicação eletrônica.

Rene Molinier (Paris 1 juny 1899 - Marsella 20 juny 1975)

Fili de pares occitans, nasqué accidentalment a Paris i passa la infantesa a Algeria, on el seu pare era funcionari. Feu estudis a l'escola normal de Tolosa de Llenguadoc i exerci com a mestre. Més tard fou professor a l'Escola Primària Superior Professional de Rodez. En aquesta situació prepara la llicenciatura en ciències naturals a la Universität de Tolosa. El 1946 entra com a encarregat de curs a la Universität de Marsella, de la qual esdevingué professor titular el 1958. Ensenyà en aquesta Universität fins a la jubilació, l'any 1969.

Looking Back: Historical Hall, 1899-1904; State Historical, Memorial and Art Building, 1905-1999; Ola Babcock Miller Building, 1999-Present, June 2013

For more than 80 years, visitors to the Iowa State Historical, Memorial, and Art Building were treated to the state’s collection of historic documents, literature, portraits, and historical, geological, and archeological artifacts. Those who visited might have memories of the spectacular sand paintings by Iowan Andrew Clemens, the variety of taxidermy Iowa animals, the pioneer Conestoga wagon in the basement, the biplane hanging from the dome ceiling, the odd display by the medical library of things removed from stomachs, or the Native American display on the third floor. This booklet is a look back at the origins of the museum. It includes some of the Historical Department reports, legislation passed by the general assembly, newspaper and magazine articles, and photographs pertaining to the museum and library. It is not intended to be an exhaustive review and documentation of displays and exhibits. It is a brief overview of the building’s history and some photographs that may bring back memories, for some, of a field trip as a student. This booklet has been created from a variety of source materials: photographs, newspaper articles, and various reports. The following have contributed: State Library of Iowa, Iowa State Historical Society, the Iowa Judicial Branch, Susan Wallace, Helen Dagley, Barb Corson, Jerome Thompson, Pam Rees, Georgiann Fischer, and Jason Mrachina.

PC Concrete Texturing, R-246, 1975

Skid resistance is a major concern of the safety engineer since wet pavement conditions are present for approximately 18% of the total accidents in Iowa according to studies by the Traffic and Safety Department. Many of these accidents may be influenced by the low skid resistant quality of the pavement. The size, shape, type, and arrangement of the concrete's particles interrelate with each other in a complex manner to give us frictional resistance. The purpose of this investigation was to determine which method of texturing provides the best skid resistance properties on portland cement concrete pavement.

Evaluation of the Argentine Nondestructive Test for Determining Concrete Compressive Strength, R-269 and MLR-75-2, 1975

The compressive strength of concrete is an important factor in the design of concrete structures and pavements. To assure the quality of the concrete placed at the project, concrete compressive cylinders are made at the jobsite. These cylinders undergo a destructive test to determine their compressive strength. However, the determination of concrete compressive strength of the concrete actually in the structure or pavement is frequently desirable. For this reason, a nondestructive test of the concrete is required. A nondestructive test of concrete compressive strength should be economical, easily performed by field personnel, and capable of producing accurate, reproducible results. The nondestructive test should be capable of detecting the extent of poor concrete in a pavement or structure due to improper handling, placement, or variations in mixing or materials.

Aspectos genéticos do tempo para o florescimento em variantes naturais de soja

Com o objetivo de melhor entender os mecanismos genéticos do tempo para o florescimento em soja (Glycine max (L.) Merrill), foram estudados os genitores e as gerações F2 de um dialelo com a cultivar Paraná e seus variantes naturais Paranagoiana, SS-1 e Pirapó 78. Os dados foram obtidos em condições de campo com o fotoperíodo variando de 13 horas e 31 minutos, na data de semeadura, ao máximo de 14 horas e 23 minutos, 59 dias após. Não foi constatada a presença de epistasia na determinação do caráter. O principal componente de variação genética foi o aditivo. Os resultados evidenciaram que o retardamento do início do florescimento é determinado por alelos recessivos. Os alelos que condicionaram a precocidade exibiram dominância parcial. As herdabilidades nos sentidos amplo e restrito foram 99,68% e 89,96%, respectivamente. As informações genéticas sobre o tempo para o florescimento apresentadas, se avaliadas em conjunto com os resultados obtidos por outros pesquisadores, indicam que o tipo de herança depende mais dos genótipos considerados que de uma faixa fotoperiódica específica.

Au coeur de l'Atlas, mission au Maroc, 1904-1905. Préfaces de M. Eugène Étienne,... et du général Lyautey,... Note de géologie et de géographie physique, par M. Louis Gentil...

Comprend : Préface ; Note de géologie et de géographie physique ; Préface

An Investigation of Concrete Setting Time, R-265 (MLR-75-4), 1975

A water reducing and retarding type admixture in concrete is commonly used on continuous bridge deck pours in Iowa. The concrete placed in the negative moment areas must remain plastic until all the dead load deflection due to the new deck's weight occurs. If the concrete does not remain plastic until the total deflection has occurred, structural cracks will develop in these areas. Retarding type admixtures will delay the setting time of concrete and prevent structural cracks if added in the proper amounts. In Section 2412.02 of the Standard Specifications, 1972, Iowa State Highway Commission, it states, "The admixture shall be used in amounts recommended by the manufacturer for conditions which prevail on the project and as approved by the engineer." The conditions which prevail on the project depend on temperature, humidity, wind conditions, etc. Each of these factors will affect the setting rate of the plastic concrete. The purpose of this project is to provide data that will be useful to field personnel concerning the retardation of concrete setting times, and how the of sets will vary with different addition rates and curing temperatures holding all other atmospheric variables constant.

Planning for disaster : local government's role in civil preparedness,1975

This handbook deals with the duties and responsibilities of a mayor of a city, a member of a county board of supervisor or a sheriff of a county from the standpoint of their relationship with a county/municipal civil defense and emergency planing administration.

Evaluation of Crushed Limestone Rock as a Mulch Material, HR-171, 1975

Earthen fills and back slopes resulting from highway building and other construction projects pose problems with respect to erosion stabilization and establishing vegetation cover. Sediments from such slopes create stream pollution while the erosion itself results in maintenance problems. Furthermore, adverse conditions aggravated by erosion prevent satisfactory establishing of vegetative cover. A dense vegetative cover is very effective in controlling erosion but even with optimum weather and soil conditions there is a delay of about 10 weeks between seeding and the establishment of a vegetative cover. Under actual field conditions, 3 months to a year may elapse between completion of construction and establishment of a vegetative cover. A research project was initiated early in 1974 to determine the effectiveness of a rock mulch of crushed limestone aggregates in controlling soil losses on highway construction back slopes in Iowa and to find the influence of such treatments on stand establishment of grasses and legumes.

Thermoplastic Pavement Markings, HR-172, 1975

It is difficult to maintain reflectorized lane markings on high-traffic, multi-lane highways. This is particularly true of sections in urban areas where there are frequent lane changes, such as on the Des Moines Freeway, I-235. In spite of the fact that the lane markings are painted on an average of three times a year, they are frequently absent during a considerable portion of the winter period. In the summer of 1973, the office of Highway Maintenance suggested a research project using a new thermoplastic paint developed by the Prismo Universal Corporation. Because of difficulties in scheduling the work, a definite proposal was not submitted until 1974. Upon the recommendation of the Iowa Highway Research Board, the project was approved by the Iowa State Highway Commission on August 7, 1974.