Data di Pubblicazione:
2011
Citazione:
IchnoGIS : a novel method for analyzing neoichnological and sedimentological data / A. Baucon, F. Felletti, G. Muttoni. ((Intervento presentato al 28. convegno IAS tenutosi a Zaragoza nel 2011.
Abstract:
The need to understand the distribution of traces and sediments requires a method to collect, organize and synthesize the information, and to communicate ichnological and sedimentological data effectively. With these aims in mind, a new method is proposed for surveying and analyzing modern environments under an ichnological and sedimentological perspective.
IchnoGIS is a system that captures, stores, analyzes, manages, and presents neoichnological and sedimentological data that are spatially referenced. It allows to analyze spatial information, determine ichnoassociations, inspect the environmental and sedimentological significance of traces.
The IchnoGIS method consists of 6 steps:
Survey design. The first step is defining the objects of interest (ichnogenera, facies) and the sampling size.
Quadrat sampling. For each sampling site, a frame (quadrat) of a set size is placed on the substrate. Spatial coordinates, sedimentological (i.e. facies, granulometry, sedimentary structures) and ichnological attributes (i.e. abundance of each ichnogenus of interest) are recorded.
Significance tests. The method includes a number of significance tests (nearest neighbour analysis, kernel density) to assess the sampling quality. If sampling is optimal, data are investigated through statistical techniques in order to characterize ichnoassemblages and to formulate hypotheses on the factors that control their distribution.
Descriptive statistics. IchnoGIS uses spatial location as the key index variable for all other information, which are – in the simplest case – ichnogenus abundance and facies type. Several techniques are available to determine the relationship between the abundance of each trace and a specific facies. Standard practice is to create a cross tabulation containing frequency counts of ichnogenera respect to facies. Another possibility is to provide a measure of central tendency and distribution.
Ichnoassemblage analysis. The next step concerns ichnoassemblages, i.e. determine whether there are groups of traces that are recurrently associated with each other. This can be verified by cross tabulating the abundance of a trace in relation to that of another.
Spatial analysis. The most immediate way to analyze spatial relationships is a classed post map, although geostatistical interpolation techniques, based on varigram analysis, can estimate the value assumed by a variable (facies type, number of traces) in unsampled positions, producing accurate ichnosedimentary maps.
The use of IchnoGIS method has many advantages, as evidenced by its application to a case study (intertidal flats of the Grado lagoon, Italy). It reveals a precise view of biogenic structures in space, allowing the collection of ichnosedimentary data for use in sedimentological studies, palaeoenvironmental reconstitutions and quantitative modelling. Finally, the IchnoGIS is fast and cost effective: it requires only a GPS unit, a plastic or wooden frame, and standard geostatistical software (open-source or commercial).
Tipologia IRIS:
14 - Intervento a convegno non pubblicato
Elenco autori:
A. Baucon, F. Felletti, G. Muttoni
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