Dolomite Mountains and the origin of the dolomite rock of which they mainly consist: historical developments and new perspectives JUDITH A. MCKENZIE and CRISOGONO VASCONCELOS ETH-Zu ¨ rich, Geological Institute, 8092 Zurich, Switzerland (E-mail: sediment@erdw.ethz.ch) ABSTRACT Beginning in the late 18th Century, the Dolomite Mountains in Northern Italy have been the location for major sedimentological developments, from the discovery of the mineral dolomite to the formulation of the coral-reef hypothesis to explain the origin of the massive dolomite structures that define the splendid scenery of the region. Further, the Dolomite Mountains have inspired voluminous research into the origin of dolomite, questioning whether dolomite is a primary precipitate or a secondary replacement product. Recently, with the recognition that microbes can mediate dolomite precipitation, a new geomicrobiological approach, combining the study of modern natural environments with bacterial culture experiments, is now being used to calibrate or interpret microbial evidence derived from the dolomite rock record. This three-pronged methodology applied to the study of dolomite formation holds great promise for future research into the ‘Dolomite Problem’ and provides a new impetus to revisit the Dolomite Mountains in the 21st Century. Keywords Dolomieu, dolomite, Dolomite Mountains, microbial meditation. INTRODUCTION Dolomite [CaMg(CO 3 ) 2 ] is a common carbonate mineral in sedimentary rocks throughout the geological record, especially in Precambrian car- bonate rocks where it is abundant and often found in association with microbial structures; but it is rarely found forming in modern carbonate environments. Because of its rare occurrence in modern sediments, as well as the apparent inability to synthesize it under low-temperature conditions in the laboratory, the origin of dolo- mite has remained a long-standing enigma in sedimentology, often called the ‘Dolomite Problem’. Numerous publications reviewing the Dolomite Problem have appeared during the past 100 years, beginning with the classic paper of Van Tuyl (1916). More recent publications (Machel & Mountjoy, 1986; McKenzie, 1991; Warren, 2000; Machel, 2004) document and discuss in detail the many dolomite-forming models. Based on field observations and theoretical considerations, these models are constructed so that they include the various conditions that may overcome the ther- modynamic and kinetic barriers to dolomite precipitation. In this work, however, the aim is not to review the Dolomite Problem, per se, but to trace the historical developments of fundamental concepts related to the origin of dolomite as pertaining to the important contributions of the Mediterranean Realm, in particular the Dolomite Mountains of Northern Italy, to this enduring sedimentological conundrum. Additionally, a new geo-microbiological approach to dolomite investigations is presented, which promises to provide innovative insights for the Dolomite Problem in the 21st Century. DOLOMITE: THE MINERAL, ROCK AND MOUNTAINS The mountains of the Southern Tyrol Alps of the Mediterranean Realm are acknowledged widely to be the geographical area where dolomite was discovered. The Italian geologist Giovanni Arduino (1713 to 1795) is credited with the first Sedimentology (2009) 56, 205–219 doi: 10.1111/j.1365-3091.2008.01027.x Ó 2009 The Authors. Journal compilation Ó 2009 International Association of Sedimentologists 205