Guidelines for the compilation of illustrative notes

Stratigraphy

As far as stratigraphy is concerned, stratigraphic units (including recent quaternary deposits) should be described by beginning with the oldest and proceeding to the most recent ones. In the case of legends based on tectonic units, the explanatory notes may maintain the order dictated by this structural arrangement, beginning with the geometrically highest tectonic unit, in accordance with the tectonic scheme and sheet legend. The lithological description of the mapped units, obviously distinguished by constituent rock, should be sufficiently broad; it should never be more detailed than the one contained in the legend. Given that the various chapters contain data of great importance – also for application purposes – Authors should ensure that they begin with data relative to macroscopic lithological features characterising the rock and then go into detail. Information should include: constituent lithofacies; their lateral and vertical relations; colour, thickness and geometry of strata and of the unit as a whole; structure; degree of cementation, fossil content, mineralogical and petrographic association, sedimentary and flow structures, any mineralisation present and any other features that may help to identify the unit in question. Stratigraphic boundaries and relations with other units – if outcropping – must be described, paying particular attention to discontinuous ones (both discordant and concordant) and to their possible expressions (hard-ground, bauxites, paleosols, etc.). Authors must include the thickness of the unit (total or outcropping) estimated or measured in the area or neighbouring zones, paying attention to lateral variations. For sedimentary rocks Authors must provide a description of the fossiliferous association (both micro and macro) indicating the biozone characterising the units. When describing clastic, volcanic and crystalline rocks ample space should be given to their mineralogical, petrographic and chemical characteristics.
Where possible, a description should be given of the lithogenetic environment or of the formation, including, if these are contrasting, alternative interpretations by other Authors. Finally, Authors should give the age, deduced from the geometric, biostratigraphic and/or radiometric data. If believed necessary, it is possible to add diagrams, tables, maps of facies, etc., within the limits laid down in paragraph 3.2.3 – Illustrazioni del Quaderno, serie III, N. 2 del SGN (Italian Geological Service). This is also the appropriate place for a description of survey data. The final note concerns the establishment of new stratigraphic units. The great number of units known in literature, which are often local in nature, sometimes in synonymity with others, and mostly not formally defined despite their consolidated use in literature, are joined by units known and defined during the process of activities for the mapping of the 1:50,000 geological sheet. A considerable summing-up and revision process must take place in order for these units to be of use for cartographic purposes, also considering the local and regional geological characteristics. To this end, the explanatory notes can play an important role in bringing about cartographic uniformity by providing the occasion for the establishment of new units, for redefining those already in use, for carrying out correlations etc. The explanatory notes represent the ideal site for including all data (including the type sections) necessary for the definition and formal institution of the unit which shall take place by filling in a worksheet drawn up by the Italian Stratigraphy Committee of the Italian Geological Society, in the context of a programme agreement between the National Geological Service and the CNR (Italian Research Centre).

1. INTRODUCTION
2. PREVIOUS STUDIES
3. NOTES ON GEOMORPHOLOGY AND GEOLOGICAL ARRANGEMENT
4. STRATIGRAPHY
5. TECTONICS
6. ELEMENTS OF TECHNICAL AND APPLIED GEOLOGY
7. BIBLIOGRAPHICAL REFERENCES