STRATI 2013 - At the cutting edge of Stratigraphy

This 1st International Congress on Stratigraphy provides an excellent opportunity for presenting aninventory of our discipline more than 200 years after its birth and one century after the publication ofthe first treatise on Stratigraphy (Grabau, 1913) which established this subject as an entity in its ownright in the area of geosciences. The state of the art presented by the authors of the plenaryconferences and by the coordinators of the different topics makes it possible to highlight the maintrends and prospects.To begin with, it should be remembered that stratigraphy is not an abstract science or simply thefruit of computer modelling. It is an observation science that must, as a priority, be based on field datafollowed by analysis in the laboratory, and on regional studies that may combine a very great varietyof analytical methods. Those are the essential references - after having eliminated the localcontingencies - for more global interpretations.Four major features can be recognized in the development of our science over the last few decades,driven in particular by oil exploration and the study of the oceans: diversification of methods, puttinginto question, multidisciplinarity, extension of the fields of application.Diversification of methods. Besides biostratigraphy which historically was the first approach usedfor dating and correlations, many other approaches are now used such as: genetic stratigraphies,chemiostratigraphy, magnetostratigraphy (mainly geomagnetic field reversals), cyclostratigraphy,clays mineralogy, isotope geochronology, tephrochronology....Putting into question by objective and critical analysis of the different techniques and thanks tothe intersecting perspectives of researchers using different tools. Biostratigraphy has thus grownstronger through a multiplication of index fossils (particularly in micropaleontology) and has beenenriched by fruitful exchanges with other approaches (palaeoecology, taphonomy, sedimentology,palaeogeography, molecular biology, isotope geochronology, magnetostratigraphy) which have madeit possible to understand better the signification of the appearance and disappearance of taxa, evaluateany diachronism of FAD and LAD and, inversely, to contribute effectively to the reconstitution ofpalaeoenvironments on various scales and to constraint timetrees. In chemiostratigraphy, it has beenpossible to evidence the contradictory signification of various signals or the different durations ofnegative and positive carbon isotope spikes. Although cyclostratigraphy may provide incomparablemetronomes, it would seem that the durations of the various orbital parameters are not constantbecause of the chaotic behaviour of the solar system. Only, the 405Kyr eccentricity is stable at leastover the last 250 Ma and can be used for astronomical calibration of Mesozoic and Palaeozoic.Multidisciplinarity. Its growing importance, in a spirit of integrated stratigraphy, has threefavourable consequences:- greater dating and correlation accuracy, by means of an iterative process of exchanges betweenthe results of various stratigraphic methods, for instance by coupling the results of isotopicchronotratigraphy with cyclostratigraphic sequences;
- perfecting of the Geological Time Scale which provides the temporal framework for thegeosciences. The GSSPs put in place gradually since 1977 must provide stratotype boundariesmaterializing the base of each stage by using the most varied tools to propose real time linesidentifiable on the scale of the globe. A contrario, experience shows that an insufficient diversityof the specific markers is currently calling into question certain limits that must be reviewed.Furthermore, various GSSPs must still be determined and validated, in particular for theCarboniferous, Permian and Cretaceous. As for the Quaternary, must the Anthropocene - attemptto recognize formally the substantial acceleration in human deduced changes to our planet duringhistorical times - be treated as a formal chronostratigraphic unit with a golden spike?- the research of causes for planetary changes. The major tendency of stratigraphy is now to trybuilding unitary models in the organization of geological objects which are likely to show andexplain the existence of logical relations between stratigraphic signals. But it must be borne inmind that nothing is ever definitively acquired: "a geologist, like any detective, must alwayswork with multiple hypotheses and as many tools as possible to help narrow the possibilities andto discover the fascinating history of our world" (Deconinck and Oggg, this volume).Extension of the fields of application. The utilization of stratigraphic approaches is not limitedsimply to sedimentary entities and our planet. Volcanic formations are also concerned, whether forelaborating a Time Scale of Volcanic Processes or for mapping volcanic regions involving the use ofinformation provided by lithostratigraphy, chemiostratigraphy, isotope geochronology and evensequence stratigraphy. And now, various stratigraphic methods are also being used to study planets(Moon, Mars, Venus, etc.) in order to establish a Planetary Time Scale comparable to the GeologicalTime Scale for Earth.The great success of this Congress - which can be seen not only in the number of contributors andthe quality of their works, but also in the great diversity of nationalities present - bears witness to thevitality of our science and to the need to organize such forums periodically, making it possible toconfront concepts, methods and results. So, you should count on a sequel to this ....8��- perfecting of the Geological Time Scale which provides the temporal framework for thegeosciences. The GSSPs put in place gradually since 1977 must provide stratotype boundariesmaterializing the base of each stage by using the most varied tools to propose real time linesidentifiable on the scale of the globe. A contrario, experience shows that an insufficient diversityof the specific markers is currently calling into question certain limits that must be reviewed.Furthermore, various GSSPs must still be determined and validated, in particular for theCarboniferous, Permian and Cretaceous. As for the Quaternary, must the Anthropocene - attemptto recognize formally the substantial acceleration in human deduced changes to our planet duringhistorical times - be treated as a formal chronostratigraphic unit with a golden spike?- the research of causes for planetary changes. The major tendency of stratigraphy is now to trybuilding unitary models in the organization of geological objects which are likely to show andexplain the existence of logical relations between stratigraphic signals. But it must be borne inmind that nothing is ever definitively acquired: "a geologist, like any detective, must alwayswork with multiple hypotheses and as many tools as possible to help narrow the possibilities andto discover the fascinating history of our world" (Deconinck and Oggg, this volume).Extension of the fields of application. The utilization of stratigraphic approaches is not limitedsimply to sedimentary entities and our planet. Volcanic formations are also concerned, whether forelaborating a Time Scale of Volcanic Processes or for mapping volcanic regions involving the use ofinformation provided by lithostratigraphy, chemiostratigraphy, isotope geochronology and evensequence stratigraphy. And now, various stratigraphic methods are also being used to study planets(Moon, Mars, Venus, etc.) in order to establish a Planetary Time Scale comparable to the GeologicalTime Scale for Earth.The great success of this Congress - which can be seen not only in the number of contributors andthe quality of their works, but also in the great diversity of nationalities present - bears witness to thevitality of our science and to the need to organize such forums periodically, making