The importance of a stratigraphic lexicon to geoscientists has long been realized by us. It has become a kind of a preliminary guidebook to the understanding of the geology of an area to be studied. Through a lexicon, also known as nomenclature, earth scientists can find all the existing lithostratigaphic terminologies of their respective countries. It is therefore important to update the Stratigraphic Lexicon of Indonesia compiled by Marks (1957), and the result is as presented in the database.
Like most stratigraphic lexicon, the present one also contains information on the lithostratigaphic units which are available in the literature, either formal or informal ones, accompanied by name of unit, age, nomenclature, type locality, description, fossil content, thickness, distibution, environment, tectonic setting, economic aspect, remark, and reference.
Since the outset of the PELITA 1 (the first Five Year Development Program) in 1969, various geological research activities carred out by the governmental institution (either without the cooperation of foreign institutions), mining companies (in particular oil companies), academicians, and individual earth scientists have been taking place. This has brought about to Indonesia the fast growing accumulation of new geological information which include stratigraphic nomenclatures, stratigraphic concept, and tectonism. Therefore, it is natural that after 30 years of busy years the lexicon of Marks (1957) has become left far behind and in an urgent need of updating.
1856 lithostratigaphic units have beeen listed in the new lexicon. The high/vast number of the nomenclature might have been due to the facts that the geology of this country is complex being located activities the triple junction of three major tectonic plates, namely the Pasific, Indo-Australian and The Eurasian Plates moving NNW, NNE, and SSE respectively. The vast of the country may also be responsible for it, not to mention the occurrence of synonymy of same lithostratigaphic units given rise by different concepts among workers or simply due to their ignorance.
The main source of this lexicon is the 239 systematic geological maps produced by Center for Geological Survey (formerly Geological Reseach and Development Center / GRDC), covering Jawa and Madura at a scale of 1:100.000 and those outside of Jawa at a scle of 1:250.000.
By November 2001, a bound draft of the stratigraphic lexicon of the Eastern of Indonesia entitled Nomenclature Compilation of the Stratigraphy og the Eastern Indonesiaan Region was completed, followed by that of the western part entitled Nomenclature Compilation of the Stratigraphy of the western publication, the drafts have been exposed for discussions in some meeting of seminar on Stratigraphy which were held by universities, Indonesian Association of Geologists and the Center for Geological Survey it self, during which invaluable comments, suggestion, and criticisms were obtained.
As a matter of course, this present edition of lexicon is beyond perfection and therefore one may find it unsatisfactory to their need. Many things such as incosistencies, synonymies, lack of proper information, and unavoidable mistakes, are to be dealt with in the future edition. For this, we are in need of further suggestion, criticism, and contribution from those who care about the development of the stratigraphy of Indonesia.