A comparative study for assessing the influence of controls on large-scale fluvial architecture Luca Colombera, Nigel P. Mountney, William D. McCaffrey Fluvial & Eolian Research Group – University of Leeds

Overview Creation of a relational database for the digitization of fluvial sedimentary architecture: the Fluvial Architecture Knowledge Transfer System (FAKTS) Quantitative characterization of fluvial architecture applicable to: quantitative physical-stratigraphy studies develop quantitative synthetic depositional models derive constraints on subsurface predictions identify modern and ancient reservoir analogues

Approach to DB design FAKTS conceptual and logical schemes The sedimentary and geomorphic architecture of preserved ancient successions and modern rivers is translated into the database schema by subdividing it into geological objects – common to the stratigraphic and geomorphic realms – which belong to different scales of observation nested in a hierarchical fashion. FAKTS conceptual and logical schemes after Colombera et al. (2012)

Data definition – entry – classification Method Data definition – entry – classification Segmentation of fluvial architecture into geometrically-defined channel-complex and floodplain depositional elements. Channel-complexes are distinguished on the basis of criteria based on the recognition of geometrical changes and interdigitation of floodplain deposits – geologically-significant surfaces can also be considered. Floodplain elements are then defined as geometrical packages laterally or vertically neighbouring channel complexes. Kjemperud et al. (2008) Labourdette (2011)

Method LIMITATIONS common lack of 3D control; source works having variable cut-offs of size of smallest mappable units; necessity to include also summary data (e.g. channel-complex W/T scatterplot); simplistic qualitative classification in proximal- distal framework; subset attributes referring to average conditions through time, even over different time scales. Kjemperud et al. (2008) Labourdette (2011)

Architectural characterization DATABASE OUTPUT GEOMETRIES PROPORTIONS TRANSITIONS Output applied to study of: stacking patterns static connectivity channel spacing

COMPARATIVE STUDIES OF ARCHITECTURAL STYLES Architectural characterization COMPARATIVE STUDIES OF ARCHITECTURAL STYLES Example channel-complex geometrical characterization of individual FAKTS case studies: width thickness W/T aspect ratio

Aggradation rates and stacking patterns Applications/1 Aggradation rates and stacking patterns Bridge & Leeder (1979) Dalrymple (2001) Bryant et al. (1995) Wright & Marriott (1993) Assessing the role of basin-wide aggradation rate as a control on fluvial architecture and as predictor of channel connectivity

Aggradation rates and stacking patterns Applications/1 Aggradation rates and stacking patterns AR vs. cT Pearson r = 0.90 Results do not support the LAB model of fluvial architecture

BASIN CLIMATE and CHANNEL-BODY GEOMETRIES Applications/2 BASIN CLIMATE and CHANNEL-BODY GEOMETRIES Investigation of: (i) channel-complex geometries for different basin climate types and (ii) geometrical changes in response to relative variations in basin humidity After Tooth (2000)

SIGNATURE OF CHANNEL PATTERNS Applications/3 SIGNATURE OF CHANNEL PATTERNS

SIGNATURE OF DRAINAGE PATTERNS Applications/4 SIGNATURE OF DRAINAGE PATTERNS Fielding et al. (2012) Information on proximal to distal evolution still necessitates data from several systems for comparison.

Conclusions The FAKTS database permits quantitative comparative studies of large-scale fluvial architecture applicable to the determination of the signature of controlling factors and system variables on channel and floodplain organization; Other FAKTS applications include: the development of quantitative facies models; the derivation of constraints on borehole correlations; the derivation of constraints on stochastic simulations of fluvial architecture; the identification of modern and ancient reservoir analogues; the comparison of the geomorphic organization of modern rivers with preserved stratigraphic architecture.

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