APMdisc: An online computer program for the geochemical discrimination of siliciclastic sediments from active and passive margins

Abstract

An online computer program called APMdisc (Active and Passive Margin discrimination) for the discrimination of siliciclasticsediments from active and passive margin settings was written in Java along with the ZK framework. APMdisc calculates four complexdiscriminant functions (DFilr(A-P)M and DFmlr(A-P)M; DFilr(A-P)MT and DFmlr(A-P)MT), which represent linear combinations of log-ratios of allten major elements (M) and ten major and six trace elements (MT), respectively. In these equations, ilr and mlr stand for isometriclog-ratio and modified log-ratio transformations of the chemical composition of active and passive margin sediments, respectively. Theilr transformation provided the same results as the mlr as documented for five case studies of Quaternary sediments from California,Antarctica, Nigeria, India, and Japan. We also present 9 other case studies (for Neogene to Quaternary sediments from known tectonicsettings) and 11 application studies (Tertiary to Neoproterozoic sediments and sedimentary rocks) to show the functioning of themultidimensional discrimination proposed in this paper. In most cases, the results from the APMdisc were consistent with the literatureconclusions inferred from different geological and geochemical techniques. Nevertheless, APMdisc provides probability estimates forboth tectonic settings, which allows the decision to be made based on the probability concept. We also added a new Robustness moduleto APMdisc, which allows the user to test the robustness of a sample against field changes, such as weathering and diagenesis, andlaboratory analytical errors or uncertainties. This program can therefore be recommended for deciphering the margin type of olderterrains. The APMdisc program can be used online by researchers for tectonic discrimination based on sediment composition. The userscan process the data file at our web portal http://tlaloc.ier.unam.mx.