AN INTER-DISCIPLINARY, MULTI-PHYSICS APPROACH FOR RAPID MAPPING AND HYDROGEOLOGICAL CHARACTERISATION OF NEOGENE INTRA-PLATE FAULT SYSTEMS IN DEPOSITIONAL LANDSCAPES
Ken LawrieTitus MurrayRoss BrodieDavid GibsonLarysa HalasNeil SymingtonNiels B. ChristensenElliot GrunewaldMike Sandiford
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Abstract:
A recent paradigm shift has occurred in our understanding of the importance of Neogene intra-plate tectonics for surface hydrology and groundwater systems in Australia. While active deformation zones are readily identified by seismicity monitoring and high-resolution satellite and airborne terrain mapping, advances in airborne electromagnetic (AEM) technology and data optimization have enabled rapid mapping of more extensive 'blind' Neogene intra-plate fault systems in the near-surface within seismically quiescent depositional landscapes. However, to date, the geometries, displacements, and properties of these Neogene faults have remained ambiguous due to a paucity of outcrop, AEM footprint resolution, and the non-uniqueness of the conductivity models and derived hydrostratigraphy and fault geometry solutions produced by AEM equivalent inversion models. In this study, a novel, inter-disciplinary approach has been developed to characterise the hydrogeology of intra-plate fault systems within unconsolidated, near-surface depositional landscapes and underlying sedimentary basins. The approach integrates morphotectonic analysis with sub-surface mapping of hydrostratigraphy and 'blind' intra-plate fault systems using airborne geophysics (AEM, airborne magnetics) and satellite remote sensing (e.g. Landsat). Fault zone geometry and displacement is examined using both 1D and 2.5D inversions of AEM data, validated at local scales by ground geophysics (e.g. seismic reflection, resistivity and ground nuclear magnetic resonance (GMR)) and drilling. Fault zone hydrogeology has been assessed through the integration of hydrogeophysics with hydrochemistry, hydrodynamics, and studies of vegetation response to water availability (using Landsat time-series analysis). The approach has also adapted deterministic and stochastic structural analysis approaches developed for use with seismic reflection data in the oil industry, to analyse AEM datasets. This inter-disciplinary approach has revealed complex fault zone conduit-barrier system behaviour that determines lateral and vertical groundwater flow, inter-aquifer leakage and localised recharge and discharge. This approach has revealed that Neogene deformation is a 'keystone element' of the Lower Darling floodplain and other surface hydrological and groundwater systems in Australia.Keywords:
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The Camerina A to Miogypsinoides A sediments of Southwest Louisiana have provided a myriad of ideas for drillable prospects over the past 30 or more years, yet a critical question remains unanswered, concerning the authors understanding of the depositional patterns for these sediments. A regional study of the Camerina A to Miogypsinoides A sediments, combined with detailed correlations of the entire stratigraphic column, including the younger Marginulina vaginata-Marginulina howei sediment series and the older Cibicides hazzardi and Marginulina texana sediments, reveals that these sediments are normal and do not require special depositional theories for local field areas. This study also reveals that the sand depositional patterns are controlled by either the major depositional fault patterns affecting the entire Camerina A-Miogypsinoides A sediments or the major structural features present during deposition. A combination of both of these features is the most reasonable explanation when all available data are considered. A regional understanding of the structure and stratigraphy from the youngest to the oldest sediments is required before the depositional patterns for a sedimentary sequence such as the Camerina A-Miogypsinoides A can be properly understood. This can only be accomplished by complete, detailed log correlations that have been integrated with both regionalmore » and local paleontological data and, when available, with good-quality seismic data.« less
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A depositional environment, also known as a sedimentary environment, is a physiography setting where sediments are deposited. A depositional setting can be a river, a lake, a delta, a lagoon and the vast ocean. Each depositional setting imparts distinctive signatures to the sediments which also includes the imprints of the paleoclimate, flora and fauna which flourished at the time. With climate change and passage of time the physiographic setting of that depositional environment location changes and the new deposits carry the signatures of the new settings. Hence, analysis of the sedimentary column at a location helps us decipher the past depositional environments and reconstruct the paleoenvironment and geologic history of the sedimentary basin.
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Abstract TM data have been used to study the deltaic depositional systems of the Po and Adige rivers. The identification of sedimentary bodies hat have formed in well-defined depositional environments requires the reconstruction of their morphology. To this end, several interactive processing techniques have been applied to a large volume of Thematic Mapper (TM) data relative to different spectral bands and acquisition dates. When necessary, data integration has also been made. Association of genetically related depositional elements allowed the interpretation of depositional environments and developmental stages in the study area.
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The analysis of regional structure,massive core samples,palaeon to logical,logging data reveals the depositional characteristics of sand groups,the rule of depositional microfacies distrubition in p lane,develops a set of deltaic front sandstones.Deltaic front includes distributary channel deposit,far sand dam and b ranch bay m icrofacies.With macroscopic depositional settings and microscopic depositional characteristics into consideration,river mou th bar, far sand dam and branch bay m-icrofacies.With macroscopic depositional settings and micro scopic depositional characteristics into consideration.Based on the log response of different sedimentary microfacies,the distribution character of the sedimentary facies in the plane is researched,and the facies sequence of this area are summed up.
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The sedimentary facies of Neogene in Bohai sea area used to be considered as fluvial facies over a long time because of the limitation of the exploration degree. Therefore, the risks of the seal rock in the Neogene exploration were believed to be great. The standpoint has restrained the Neogene exploration in Bohai sea area. With the increasing of the exploration degree, it is recognized that Bozhong depression of Bohai sea area is one of the main catchment area for Bohai bay basin in Neogene. The lacustrine and deltaic depositional systems were discovered in Neogene in Bozhong depression in the recent years. This paper focuses on elaborating the evidences of the existence of the lacustrine and deltaic depositional systems and the characteristic of the delta depositional system(including normal lacustrine delta and braided delta).The discovery of lacustrine and deltaic depositional systems in Bozhong depression have a very important significance in the oil and gas exploration. The development area of the deltaic systems will be the major field of the exploration in Bohai sea area in the future.
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