Sedimentological Field Research Articles

Use of Low-Cost Multistripe Laser Triangulation (MLT) Scanning Technology for Three-Dimensional, Quantitative Paleoichnological and Neoichnological Studies

Abstract The purpose of this paper is to test the application of a new, low-cost ($2995.00 US), multistripe laser triangulation (MLT) scanner and three-dimensional (3D) software for semiquantitative and quantitative analyses of ichnofossils and modern traces. The goal of this research is to improve on existing analytical techniques and apply new methods to 3D digital models of ichnofossils and modern traces. Objectives are to (1) provide researchers with new ways to develop and test hypotheses quantitatively in the fields of paleoichnology, neoichnology, sedimentology, and soil science, and (2) discuss uses, advantages, and limitations of MLT technology related to ichnology. We scanned and created digital models of a variety of mostly continental ichnofossils and modern terrestrial traces produced by invertebrates and vertebrates. Visual methods applied include making uniformly colored specimen surfaces, stereo pairs, anaglyph stereo images, animations, and cross sections. Quantitative methods applied include measuring distances, tortuosity indices, and angles, and producing contour maps of tracks. Two of the most useful properties measurable from digital models are surface area (SA) and volume (V); these are used rarely in ichnology because they are difficult to measure with traditional methods. We use SA to calculate area exploited and introduce a method of quantifying surface roughness adapted from research on soil surfaces. We measure V of burrows, tracks, and coprolites, as well as introduce a new measure termed “volume exploited.” We hypothesize that different tracemakers make burrows with characteristic V to SA ratios; this is partially supported by statistical tests of previously published data. We also use V to SA ratios to determine relative compactness—a metric adapted from building physics. Digital models ensure perpetuity of specimens because they preserve 3D data that can be used to make physical copies, placed in museums, and disseminated easily to researchers and educational institutions of all levels. Data from digital models can be used to interpret ichnocoenoses, bioturbation rates, and pedogenic properties and processes in soils and paleosols. Note that MLT scanning digitizes only surfaces of objects, so it is best suited for exogenic traces and casts of endogenic traces.

Fluvial architecture as a response to two-layer lithospheric subsidence during the Permian and Triassic in the Iberian Basin, eastern Spain

The stratigraphy of a sedimentary basin is mainly the result of the long-term response of a depositional surface to prolonged subsidence. However, the real nature of interrelations between fluvial architecture and subsidence is still unknown. Herein, we present new data on these relationships by combining the results of detailed sedimentological field work with data acquired through automated forward modelling and backstripping for the alluvial Permian and Triassic sediments of the SE Iberian Ranges. Using this methodology, we determined tectonic subsidence of the basin by means of backstripping analysis and crust and lithospheric mantle stretching factors ( δ and β , respectively) using forward modelling technique. Results indicated that a configuration of two individual and independent layers during lithospheric subsidence for each tectonic phase fit better for this time of the studied basin evolution than the assumption of subsidence due to a single layer spanning the whole lithosphere. For this study, we simplified fluvial geometries as two main types: isolated (I) and amalgamated (A), with subtypes in each case. Different order bounding surfaces (b.s.) were distinguished in the field, although we only selected those affecting the whole basin under study. These included those b.s. of clear tectonic origin, ranging from individual basin boundary-fault pulses produced over periods of approximately 1 My to those arising from major tectonic events, such as the beginning of extension in the basin, causing major changes in basin geometry over periods of 3–5 My. The comparison of δ and β values and fluvial geometries for each identified tectonic phase in the basin evolution, revealed some possible relationship between subsidence and fluvial geometry: Sections showing the most varied fluvial architectural geometries, including ribbon and nested forms, were related to higher β and δ stretching factors values indicating tectonic phases of greater stretching and subsidence. When both stretching factors were similar and close to 1, fluvial geometry was basically reduced to amalgamated geometry type. Wider ranging of fluvial geometries was associated with stages of basin development in which crust and upper mantle activities differed, that is, showing larger differences of β and δ stretching factors values. The related slope changes are proposed as the main surface control of fluvial styles. Combination of subsidence with other possible controlling factors such as avulsion rate, climate or budget of sediments, gives rise to the definitive alluvial architecture of a basin.

A new approach for outcrop characterization and geostatistical analysis of a low-sinuosity fluvial-dominated succession using digital outcrop models: Upper Triassic Oukaimeden Sandstone Formation, central High Atlas, Morocco

The use of digital outcrop models in combination with traditional sedimentological field data improves the accuracy and efficiency of qualitative and quantitative characterization of outcrop analogs for reservoir modeling purposes. In this article, we apply an innovative methodology of outcrop characterization to an Upper Triassic fluvial-dominated system, exposed in extensive outcrops with limited three-dimensional (3-D) exposure. Qualitative analysis of the study outcrop allows the subdivision of the formation into three architectural intervals. Each interval can be further subdivided into subintervals on the basis of architectural style. This subdivision provides information on reservoir compartmentalization, which is used for zonation of the geocellular model. Qualitative analysis also provides valuable information on reservoir facies distribution. A new technique termed perpendicular projection plane is presented as a tool for quantitative analysis of outcrops with reduced 3-D exposure. This technique improves the accuracy of apparent width measurements of geobodies exposed in outcrops, which are subparallel to paleoflow. The quantitative analysis provides a detailed data set of geobody dimensions to use as conditioning data for analog reservoir models. Statistical analysis of the dimensions provides empirical relationships to apply in subsurface analog systems to reduce uncertainty related to stochastic modeling approaches.

Sedimentology of an intra-montane rift-controlled fluvial dominated succession: The Upper Triassic Oukaimeden Sandstone Formation, Central High Atlas, Morocco

Triassic successions in the High Atlas of Marrakech (Morocco) provide excellent outcrop analogues for continental fluvial systems within an intra-montane rift basin and allow the study of facies distribution and controls on deposition. This paper focuses on the analysis of the Oukaimeden Sandstone Formation (F5), a fluvial dominated formation deposited in an active rift setting. Combination of traditional sedimentological field analysis with modern digital data capture techniques (e.g. spectral gamma-ray, LIDAR terrestrial scanner imaging) allows a detailed description and interpretation of the facies. The Oukaimeden Sandstone Formation is composed of channel sandstone bodies alternating with lenticular shaped fluvial bar sandstones and overbank mudstone deposits. Alternating with the fluvial facies, aeolian sandstones and alluvial fan deposits are also observed. Changes in architectural style are used to subdivide the formation into three members. The lower member (Lower Oukaimeden ) was deposited by an ephemeral braided system. The middle member (Middle Oukaimeden) records a change to perennial braided fluvial conditions in response to tectonics combined with a change in climate towards more humid conditions. The upper member (Upper Oukaimeden) is characterized by the return to ephemeral conditions, which combined with the occurrence of aeolian dunes, is interpreted to record increased aridity. The upper part of the member exhibits tidal influence, related to the first marine incursion into the basin. The Oukaimeden Sandstone Formation provide a well documented outcrop example of deposition within an intra-montane setting influenced by a combination of tectonic and climatic controls.

Analogue modelling of the interaction between tectonics, erosion and sedimentation in foreland thrust belts

The structure and dynamic evolution of a mountain belt piedmont are controlled by strong interactions between tectonics, surface processes (erosion, sedimentation), and climate. Studying these couplings relies on detailed geometric and kinematic analysis of morphostructural markers (folds, faults, terraces, alluvial surfaces) and analysis of syntectonic sedimentation. To study quantitatively how these markers form, evolve and record deformation, we developed a new analogue modelling approach using a specific composite granular material. The originality stands in the simultaneous modelling of orogenic deformation mechanisms and erosion–transport–sedimentation processes, but also in the use of techniques allowing quantitative measurement of morphostructural evolution. This methodology opens new perspectives in the fields of geomorphology (relief dynamics), seismotectonics (study of active faults), and sedimentology (including sequential stratigraphy).

A GIS-based method to calculate flow accumulation by considering dams and their specific operation time

This paper presents a new approach to calculate flow accumulation with geographic information systems (GIS). It is based on the well-known D8 single-flow algorithm that is extended to consider the trap-efficiencies of dams and their specific operation time. This allows realistic calculations of flow accumulation for any time period. The new approach is not restricted to surface water runoff but can be applied to all kinds of mass fluxes like suspended or dissolved sediment load (weighted flow accumulation). To facilitate its use, two GIS extensions for ArcView and ArcGIS have been developed. This paper presents the principles of the new approach, the functionality of the extensions and gives some applications in the fields of hydrology and sedimentology.

Polyphase deformation of diapiric areas in models and in the eastern Prebetics (Spain)

Fingerlike bodies of evaporite rocks have been observed in many regions affected by multiple tectonic phases, such as the Atlas, the Pyrenees, or the Zagros Mountains, where they have been interpreted as fault-plane diapiric injections or collapse-related salt welds. In this article, we suggest a new interpretation of these structures as squeezed diapirs based on detailed structural and sedimentological field data of the Bicorb–Quesa diapir (eastern Prebetics) and offer five analog models, which simulate the polyphase deformation of the eastern Prebetics. In this area, diapirs formed from the Oligocene to Langhian during an extensional phase related to the opening of the Valencia Trough. These diapirs were later affected by a Serravallian contractional phase, which inverted the preexisting grabens and created new folds and thrusts. The preexisting diapirs were necked and/or squeezed, forming secondary welds with a fingerlike geometry that isolated the diapir bulbs from their source layer. Extrusion of diapiric material was also accelerated during this phase, but no new diapirs formed. Finally, the area was again affected by an extensional phase during the Tortonian, which reactivated the normal faults and created a new set of diapirs. The new diapirs formed where the overburden was thinner, that is, at the toe of the major reactivated faults. Commonly, these faults coincide with the bounding faults of the major grabens formed during the first extensional phase, and therefore, the new diapirs grow close to the location of the squeezed diapirs. The models also show that the faults created during the initial extension prevailed as the main focus for deformation during the polyphase history. Deformation in the overburden and the viscous layer was mainly accommodated along the major grabens formed during the first extensional stage. During shortening, the initial major grabens deformed as complex anticlines, and during the subsequent extensional phase, most deformation occurred by the collapse of these anticlines along preexisting faults, fault welds, and the flank of the squeezed diapirs. The source layer is compartmentalized, accumulating and withdrawing material in the same locations (the initial grabens and horst). As a result, the source layer is easily depleted beneath the initial horst, forming primary welds.

Ice‐cored drumlins at the surge‐type glacier Brúarjökull, Iceland: a transitional‐state landform

AbstractThis paper presents data on a glacial landform that, to our knowledge, has not previously been described in the literature: the ice‐cored drumlin. The study area is the forefield of the surge‐type glacier Brúarjökull at the northeastern margin of the Vatnajökull ice cap, East Iceland. Based on sedimentological field investigations and aerial photograph interpretation, a qualitative model for the formation of ice‐cored drumlins is proposed. The drumlin core consists of stagnant glacier ice from a previous advance and bubbly ice formed by snowdrifts, which were incorporated during the most recent advance—the 1963–64 surge. This advance deposited a mantle of basal till and streamlined the ice‐cored moraines. Till deformation and deposition on the drumlin ice‐core is facilitated by a substratum of low‐permeability ice‐cored moraines.In the present climate, the ice‐core is subject to melting and the drumlin landform will degrade. The ongoing melting of the core and re‐sedimentation of the till cover cause the originally streamlined subglacial landform to develop into a patch of hummocky moraine surrounded by a basal till sheet. Thus, ice‐cored drumlins are a transitional‐state landform in the surging glacier landsystem at Brúarjökull rather than a ‘final’ landform. Copyright © 2005 John Wiley & Sons, Ltd.

The Grès d’Annot in the Annot syncline: outer basin-margin onlap and associated soft-sediment deformation

Abstract The Grès d’Annot onlap on the outer basin margin has been extensively studied, but a number of important issues and critical outcrops remain controversial. A new geological map of the Annot syncline is here presented, supplemented with structural and sedimentological field observations. The mapped onlap traces in Annot reveal a curved, east-concave surface, with distinct westward shift of the successive onlap lines. The inferred onlap direction at Chalufy is to the SW, the only orientation compatible with the movement of the normal fault near Cabane des Abeurons. The similarity of the onlap relations between the areas of Annot and Chalufy, together with the structural features of the Annot syncline, support the concept of a common outer basin margin, rather than of a northern confinement of the Annot turbidites. The margin-onlap setting involved a specific style of syndepositional deformation. As a large, high-density turbidity current arrived on the basin-flank slope, it rapidly decelerated, thickened and dropped its coarse load, while being simultaneously deflected away from the slope. The associated normal stress and overpressure caused sub-horizontal injection and de-lamination of the soft substrate, with the tangential strain curling up the detached substrate slice into an overturned synclinal structure. The process provides an efficient way to incorporate fragments of mudstone and thin-bedded sandstone within the still moving highly-concentrated flow, eventually constituting the chaotic intervals within ‘tri-partite’ beds as the examples observed at the Braux section.

Determination of Ore Concentrates by Energy Dispersive X-Ray Fluorescence Spectrometry

EDXRF analysis has broad applications in the quantitative analysis of major and minor elements in geological, geochemical, and environmental studies, including the fields of sedimentology, stratigrapy, geochemistry, and mineral exploration. Evaluation of its potential for the analysis of major and minor elements in Bozalt and Dedemaksut ores were performed. Physical basis of used standard addition method, experimental set-up, the procedure of sample preparation and the results of analysis were presented. The correlation coefficients for each of elements analyzed (r greater than 0.986) were achieved.

Geometric morphometrics and geological shape-classification systems

Many areas of geological inquiry involve the description and/or comparison of shapes. While various morphometric tools have long been available to facilitate these types of comparisons, by far the most common approach to such form-classification has been via the creation of a semiquantitative scale of morphological exemplars, type specimens, etc. to which unknown structures, objects, or specimens can be compared. Such form-scales are ubiquitous—either in terms of text-based descriptions or illustration sets—throughout the geological literature. However, students, and even experienced geologists, often have difficulty using such scales and achieving consistent results. Investigations of three such scales drawn from the fields of sedimentology, paleontology, and geomorphology using the analytical tools of geometric morphometrics suggests that one reason for this difficulty is that the exemplars drawn from sets of real objects (1) often exhibit shape differences other than those under nominal consideration or (2) are used to represents object classes whose boundaries are insufficiently documented or described. Herein, strategies are developed that employ the ordination and modeling capabilities of eigenshape analysis to correct these deficiencies and devise sets of new, more representative, and easier to use shape-classification systems. By employing these approaches, augmented where necessary with formal statistical analyses, geologists can improve the sophistication, accuracy, and reproducibility of their morphological inferences. In doing this, they will also improve the reliability of their hypotheses tests.

ABSTRACT: The Interaction Between Basin-Scale Extensional Folding and Sedimentation in a Supradetachment Basin

Hanging-wall deformation in extensional settings has the potential to create complex syntectonic sedimentary packages. These sediments record interplay between sedimentation and synextensional folding, as recorded in Grasshopper rift basin, SW Montana. As a result of this interaction, Grasshopper basin, has a complex, threedimensional stratigraphic and structural geometry. Large, basin-scale extensional folds developed in this north-trending Paleogene supradetachment basin during extensional deformation. A major N-trending anticline, 10 km long and 1.8 km in structural relief, occupies the western half of the basin. Approximately perpendicular to the anticline, a major syncline 8 km long and roughly 0.5 km in structural relief plunges 88 toward an antiform in the underlying listric detachment fault. Sedimentologically, we interpret the basin as a sediment starved lacustrine system dominated by southward axial infilling and lesser, yet significant, transverse sediment influx. The basin contains about 4 km of Tertiary basin fill. Stratigraphic and sedimentological analyses reveal that several basin-scale lacustrine transgressions, facilitated by slip on the eastern border-fault and increased accommodation space due to folding, laterally shifted depositional environments. Interruptions in the southward progradation of the fluvial-deltaic facies are marked by the north-northeast retreat of conglomerates and sandstones on the north limb of the transverse syncline. In the mid to late stages of basin deformation, current data suggests that the longitudinal anticline evolved. To help visualize the large-scale stratigraphic and structural features of this basin, we integrated seismic data and structural, stratigraphic, and sedimentological field data into three-dimensional structural models (2D/3DMove from Midland Valley Exploration) of the basin.

Structural cross sections through the Corinth-Patras detachment fault-system in Northern Peloponnesus (Aegean Arc, Greece)

Structural mapping in northern Peloponnesus reveals the emergence of an E-W striking, more than 70km long, low angle detachment fault dipping to the north beneath the Gulf of Corinth. This paper describes four north-south structural cross-sections in northern Peloponnesus. Structural and sedimentological field observations show that in the studied area the normal faults of northern Peloponnesus branch at depth on this major low angle north-dipping brittle detachment. The southern part of the detachment and the related normal faults are now inactive. To the north, the active Helike and Aigion normal faults are connected at depth with the seismically active northern part of the detachment beneath the Gulf of Corinth.

Sedimentology, stratigraphy, and geomorphology of glacial Lake Calgary at Cochrane, Alberta, Canada

Stratigraphic and sedimentologic field data in the Cochrane, Alberta, area demonstrate that glaciolacustrine sediment comprising the Calgary Formation underlies glaciofluvial and fluvial sediment of the Bighill Creek Formation, previously dated at 11.4 ka BP. A continuous, conformable contact between sediments of glacial Lake Calgary and underlying till indicates that the lake was coeval with initial deglaciation of the area. The lake formed during retreat of the Cordilleran ice up the Bow Valley that was once previously coalescent with the Laurentide Ice Sheet. Rhythmic, graded, and convoluted glaciolacustrine sediments record continuous and high rates of sedimentation in this reach of glacial Lake Calgary, further implying that the lake formed early in deglacial time.

Sedimentology, stratigraphy, and geomorphology of glacial Lake Calgary at Cochrane, Alberta, Canada

Stratigraphic and sedimentologic field data in the Cochrane, Alberta, area demonstrate that glaciolacustrine sediment comprising the Calgary Formation underlies glaciofluvial and fluvial sediment of the Bighill Creek Formation, previously dated at 11.4 ka BP. A continuous, conformable contact between sediments of glacial Lake Calgary and underlying till indicates that the lake was coeval with initial deglaciation of the area. The lake formed during retreat of the Cordilleran ice up the Bow Valley that was once previously coalescent with the Laurentide Ice Sheet. Rhythmic, graded, and convoluted glaciolacustrine sediments record continuous and high rates of sedimentation in this reach of glacial Lake Calgary, further implying that the lake formed early in deglacial time.

Translocated Plio-Pleistocene drainage systems along the Arava fault of the Dead Sea transform

Geomorphic and sedimentologic field studies and analyses of LANDSAT 5 images and topographic maps indicate 15 km of left-lateral displacement of a Pliocene large stream and alluvial fans along the Dead Sea transform in southern Israel and Jordan. In the central Arava valley, a rift valley located along the transform, there is a notable discrepancy between the number and location of the feeding drainage basins within the eastern margins of the Arava valley and those of the alluvial fans and the cross-rift large stream. A few of these large alluvial fans lack any feeding drainage basin. Furthermore, east of the large stream there is no drainage basin that could have fed it. These discrepancies between the physiography, locations, sizes, and lithological compositions of the feeding drainage basins and of the alluvial fans can be explained by 15 km of left-lateral movement since the Late Pliocene or the Early Pleistocene along the Arava-Dead Sea segment of the transform. This is one of the largest displacements of a landform and surficial alluvial deposit in the world. However, the resulting average long-term rate of movement is relatively small (0.3–0.75 cm/year).

Block hydraulic conductivity of cross‐bedded fluvial sediments

This paper concerns the three‐dimensional block hydraulic conductivity of blocks of limited size in cross‐bedded sediments of meandering rivers. Based on a simplified sedimentological model of a single point bar, a stochastic model is proposed to simulate the spatial distribution of core scale conductivities within point bar deposits. The required parameters for these simulations are obtained from actual hydraulic conductivity measurements and sedimentological field data. The simulations are then used to calculate the three‐dimensional block conductivity tensor with a numerical upscaling procedure. The stochastic simulation model is used to investigate the influence of slope and aspect angle of the cross‐beds and the core scale anisotropy ratio on the block hydraulic conductivity. It is expected that the off‐diagonal elements of the block conductivity tensor generally cannot be neglected. The core scale anisotropy ratio, which reflects the small scale layering within the cross‐beds, can potentially have a significant impact on the elements of the block conductivity tensor.

TraPhyC-BV: A hydrologic information system

Digital Elevation Models are used to automatically map the drainage network, the stream channel and divide networks of a watershed. This has been done with the TraPhyC-BV software package. Construction of a code describing the network may form the basis for an efficient hydrologic information system. This form of discretization of a watershed produces natural units for problems involving surface or subsurface water flow. This methodology is designed to aid in the parametrization of a distributed components approach to watershed simulation in the fields of hydrology, sedimentology and geomorphology.

Early Cretaceous environments

A one day meeting of the British Sedimentological Research Group (BSRG), convened by K. G. Taylor and A. H. Ruffell, was held at the Postgraduate Research Institute for Sedimentology, University of Reading on 23 June 1992. The meeting set out to consider what is known about palaeoenvironments of the NW European early Cretaceous and to present current areas of new research that may significantly expand our understanding of this topic. Over 50 people attended this multidisciplinary meeting, coming from the fields of sedimentology, geochemistry, palaeontology and tectonics. There were 13 speakers and five poster presentations. Financial assistance from the BSRG to speakers from overseas is gratefully acknowledged. The Institute is also thanked for the use of their facilities. After a brief welcome by the conveners, D. J. Batten (Aberystwyth University) gave a talk reviewing his work on the palynology of NW European Wealden sediments. In this he stressed how palynological data, integrated with other available evidence, can contribute significantly to interpretations of early Cretaceous environments and should be utilized more by sedimentologists. In particular, the total recoverable organic matter in a sample should be studied, not just the identification of miospores and dinoflagellate cysts. J. Eyers (Open University) described how detailed sedimentology, grain-size analysis and gamma-ray logging have been used to correlate the Lower Cretaceous of the Bedfordshire Province. Using isopachyte maps, she was able to show that basement structures, reactivated as a result of North Sea rifting, were a major control on sedimentation. She also tentatively compared a combined

Paleogeographic Considerations of the Barbacoas Platform Western Border During Paleocene-Middle Eocene, Trujillo State, Venezuela

Stratigraphic and sedimentological field information of the Chejende-Cuicas area, and subsurface well data (Butaque-1S) have been integrated to analyze the paleogeographic evolution of Barbacoas Platform. Both localities are in the Trujillo state, western Venezuela and they are 18 km apart. A relatively narrow continental platform during Paleocene times can be inferred from the existence of Paleocene rocks of the Rancheria Formation, deposited in outer and middle neritic environments. This formation probably grades laterally towards the east and northeast, into the Trujillo Formation (Paleocene-early Eocene), which was deposited in a middle to upper bathyal environment in turbiditic conditions. Paleocene units grade upwards into the Misoa Formation, deposited in deltaic to coastal marine environments. This suggests a regressive progradation over slope and platform during early to early middle Eocene times. Eocene sedimentation ends with the transgressive Caus and Pauji formations, typical of upper bathyal to outer neritic conditions. Low sedimentation and subsidence rates in the platform in the Chejende area is inferred by the marked difference between Rancheria and Misoa formation thicknesses in this area (95 m and 40 m) and the Butaque-S well (520 and 175 m).