Luis Pedro Fernández

Mélanges and other types of block-in-matrix formations in the Cantabrian Zone (Variscan Orogen, northwest Spain): origin and significance

Block-in-matrix formations in the Variscan foreland of Spain (Cantabrian Zone) occur in two different geological settings. The major block-in-matrix formations are mélanges, which appear as carpets beneath or ahead of submarine thrust systems. These mélanges may reach up to kilometric thickness and are mostly composed of broken formations (boudinaged sequences) of late Carboniferous age and scattered ‘exotic’ blocks derived from older Palaeozoic formations. Moreover, the mélanges in the Cantabrian Zone also include subordinate debris flow deposits with a chaotic block-in-matrix fabric (olistostromes). The source of the mélange blocks was the front of advancing nappes, chiefly the upper part of the nappe stacks. Therefore, the Cantabrian mélanges are interpreted as originated through submarine sliding and slumping associated with steep slopes at the orogenic front. The different types of rock bodies of these mélanges may be related to the degree of lithification of the sediments or rocks during slumping. So, broken formations are boudinaged sequences where the boudins or blocks resulted from extensional faults developed in lithified or semilithified limestones and sandstones, whereas the unlithified muddy matrix underwent continuous deformation. The scattered ‘exotic’ blocks ranging in age from early Cambrian to early Carboniferous were incorporated into the mélanges as individual blocks from competent well-lithified formations, originally located in the lower part of the nappe stacks. Although the Cantabrian Zone mélanges include olistostromic intervals, most of the olistostromes of this zone occur in a different geological setting. They are usually intercalated in the normal marine deposits of the Variscan foreland basin and, in contrast to the mélanges, they are mostly related to the margins of carbonate platforms, ahead of moving nappes. Finally, other instances of olistostromes are related to slopes generated by limb rotation of growth folds, which developed on submarine wedge-top successions.

Earliest Pragian (Early Devonian) corals and stromatoporoids from reefal settings in the Cantabrian Zone (N Spain)

The oldest reefal episode in the Cantabrian Zone (earliest Pragian) consists of small biostromal patch reefs, mainly built by corals and stromatoporoids, and developed on a storm-dominated ramp. Four outcrops provide the stratigraphic framework in which these reef facies developed, and these permitted an interpretation of their depositional setting in terms of a relatively distal or protected shelf. We systematically describe three species of rugose corals, five species of tabulate corals, and six species of stromatoporoids. This fauna is allocated to three Pragian fossil associations. Association 1 is mainly composed of massive tabulate corals and stromatoporoids. Association 2 contains dominant branching rugose and tabulate corals. Finally, association 3 is represented by tiny massive tabulate corals. Each association occurs at a specific location within a framework of high-frequency deepening upward cycles, being related to a specific depositional setting. This mode of occurrence suggests that their development was tuned by relative base-level oscillations, forming during rises that took the sea-bottom to relatively deep or sheltered conditions, with rare reworking by storm-related currents. Finally, a comparison of this reefal fauna with examples of similar age from elsewhere is presented in order to explore their affinities.

Foramanifera and biostratigraphy of the Valdeteja Formation stratotype (Carboniferous, Cantabrian Zone, NW Spain)

SummaryThe Valdeteja Formation is a lithostratigraphic unit of essentially Bashkirian age widely distributed through the Cantabrian Zone (Iberian Massif, NW Spain). It consists mainly of limestones with subordinate limestone breccias and some marly intercalations, deposited in shallow carbonate platforms and in the adjacent slope and basin settings (see Eichmüller, 1985). Its considerable thickness, rather continuous stratigraphic record and large lateral extent in the Cantabrian Zone have attracted the attention of geologists who have carried out a number of studies dealing with the palaeontological content, sedimentology, and palaeogeography of this formation. In spite of these diverse investigation, the precise age of the Valdeteja Formation, particularly the age of several fossiliferous beds defined at its stratotype, as well as the age of the top of the formation, remain obscure.This paper studies the foraminifera (mainly fusulinoideans) yielded by several beds throughout the type-section. The biostratigraphic information provided by these faunas allows us to establish the age of the mentioned beds in terms of the Russian stratigraphic scale. It confirms an early Moscovian age for the top of the type section, a matter of discussion for a very long time. Moreover, this research may have general interest in Carboniferous stratigraphy since it provides data on the fusulinoidean assemblages existing in western Europe during Bashkirian time, an interval containing a rather poor fossil record in this part of Eurasia.

Cambrian–Ordovician conodonts from slump deposits of the Argentine Precordillera: new insights into its passive margin development

Fil: Voldman, Gustavo Gabriel. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro Cientifico Tecnologico Conicet - Cordoba. Centro de Investigaciones en Ciencias de la Tierra. Universidad Nacional de Cordoba. Facultad de Ciencias Exactas Fisicas y Naturales. Centro de Investigaciones en Ciencias de la Tierra; Argentina

Constraining the Timing and Amplitude of Early Serpukhovian Glacioeustasy With a Continuous Carbonate Record in Northern Spain

During the Late Paleozoic Ice Age (LPIA, 345–260 Ma), an expansion of ice house conditions at 330 Ma caused a nearly synchronous, global unconformity. Subaerially exposed paleotropical carbonates were dissolved by meteoric waters, mixed with the light terrestrial carbon, and recrystallized with overprinted, diagenetic dC values. In Northern Spain, development of a rapidly subsiding foreland basin kept local sea level relatively high, allowing continuous carbonate deposition to record dC without meteoric overprint. The Spanish sections show a 2& increase in dC that can be modeled as the ocean’s response to the creation of a significant light carbon sink through widespread meteoric diagenesis of marine carbonates during the near-global hiatus. About 15–35 m of sea level fall would have exposed a large enough volume of carbonate to account for the positive excursion in dC of oceanic DIC. Combining the dC data with high resolution biostratigraphy and new ID-TIMS U-Pb zircon ages from interbedded tuffs, we calculate that the depositional hiatus and glacioeustatic fall caused by the early Serpukhovian phase of ice growth lasted for approximately 3.5 My.

Reduction of rejections in cold rolled strip welding by intelligent analysis of image and process data

Welding plays an important role in the metallurgic process, being a critical part of continuous processes. The early detection of welding defects is a key aspect to guarantee productivity. There are factories in which the welding testing is performed visually by an operator. In this scenario, the physiological and psychological aspects of the operator can determine the productivity due to unnecessary repetitions of welds. This paper proposes an on-line intelligent system for operator support. The goal is to reduce the unnecessary repetitions of welds. The proposed method uses data mining and machine learning techniques fed by the information extracted from the process data and from the data obtained by an infrared camera, creating an objective model that estimates the weld reliability. Flexibility and adaptability are two key concepts in the proposed design.