Doleran Complex

Doleran Complex
Name	Doleran Complex
Type	Geological complex
Period	Neogene–Quaternary
Primary lithology	Basalt, andesite, tuff
Otherlithology	Sediment, conglomerate, volcanic breccia
Namedfor	Doleran Basin
Region	Transmontane Belt
Country	Multinational
Subunits	Doleran Basalt Member; Verin Tuff Member; Karas Conglomerate
Thickness	up to 2,800 m
Extent	120,000 km2

Doleran Complex is a broad volcanic-sedimentary succession characterized by extensive mafic to intermediate volcanism, pyroclastic deposits, and intercalated sedimentary sequences. The Complex crops out across a transmontane belt and records a prolonged history of arc-related magmatism, basin evolution, and volcaniclastic sedimentation from the late Neogene into the Quaternary. It is a focus of multidisciplinary studies spanning petrology, geochronology, paleontology, and economic geology.

Introduction

The Doleran Complex occurs in a regional tectonic corridor that has been compared with arcs such as Cascade Range, Izu–Bonin–Mariana arc, Andean Volcanic Belt, Aleutian Arc, and Anatolian Plateau examples. Its significance has been highlighted in syntheses published by researchers affiliated with institutions like the United States Geological Survey, Geological Society of London, Chinese Academy of Sciences, Max Planck Society, and Universidad Nacional Autónoma de México. Key debates involve correlations with formations exposed in the Sierra Madre Occidental, Himalayan Orogeny-related basins, and basalts of the East African Rift.

Geology and Lithology

Lithologies include coherent basalts, andesites, dacites, extensive tuffs, ignimbrites, and volcaniclastic conglomerates analogous to units described in the Columbia River Basalt Group, Deccan Traps, Emeishan Large Igneous Province, and smaller-scale arc systems like Kurile Arc. Petrographic assemblages show plagioclase, clinopyroxene, orthopyroxene, amphibole, and accessory titanomagnetite and zircon resembling suites reported from Sierra Nevada (U.S.) intrusive complexes and Iberian Pyrite Belt volcanogenic systems. Hydrothermal alteration produces chlorite, sericite, and zeolite facies minerals related to mineralization styles seen at El Teniente, Bingham Canyon Mine, and Grasberg Mine.

Stratigraphy and Age

Stratigraphic subdivisions are typically formalized as the Doleran Basalt Member, Verin Tuff Member, and Karas Conglomerate, correlated using radiometric dates, magnetostratigraphy, and biostratigraphic markers. Ages obtained by 40Ar/39Ar dating and U–Pb zircon geochronology span late Miocene through Pleistocene intervals, comparable to chronologies established for the Sierra Chichinautzin and Hengduan Mountains volcanic records. Magnetostratigraphic polarity reversals correlate with the geomagnetic polarity timescale used in regional correlations with sections such as the Matuyama–Brunhes boundary.

Paleontology and Fossil Record

Fossil occurrences are mainly within interbedded sedimentary lenses and lacustrine strata, yielding vertebrate assemblages, freshwater mollusks, and plant macrofossils comparable to faunas from the Siwalik Group, Hell Creek Formation, and Florissant Fossil Beds. Palynological studies recover pollen and spores tied to vegetation assemblages documented in the Neogene of Europe and the Pleistocene of North America, aiding paleoenvironmental reconstructions. Trace fossils, including burrows and vertebrate trackways, provide behavioral data analogous to ichnofossils described from the Eocene Green River Formation.

Distribution and Occurrence

Outcrops extend along a belt extending over several hundred kilometers, with major exposures in basins and fault-bounded blocks reminiscent of distributions in the Basin and Range Province, Pannonian Basin, Altiplano–Puna Plateau, and parts of the Tibetan Plateau. Subsurface continuations are intercepted by boreholes drilled by agencies such as British Geological Survey and local petroleum companies, revealing thickness variations and interfingering with sedimentary successions comparable to those in the North Sea Basin and the Gobi Basin.

Economic Importance and Uses

The Complex hosts volcanogenic massive sulfide-style and porphyry-associated mineralization, with occurrences of copper, gold, silver, and base metals similar to deposits at Kujalleq, Cerro Negro, Yanacocha, and Kupferschiefer-adjacent systems. Geothermal gradients and hydrothermal alteration make parts of the Complex prospective for geothermal energy developed in areas like The Geysers, Icelandic fields, and the Cerro Prieto field. Aggregate, dimension stone, and clay resources exploited locally parallel uses of volcanic rocks in the Roman Empire roadstone trade and modern construction in regions such as Marmara Region.

Research History and Current Studies

Early mapping and descriptions were produced by survey teams from organizations including the Ordnance Survey, Geological Survey of India, and national geological surveys during 19th–20th century campaigns echoing historical work on the Appalachian Mountains and Alps. Contemporary research integrates petrology, isotope geochemistry, and remote sensing from groups at Massachusetts Institute of Technology, ETH Zurich, Université Grenoble Alpes, and national laboratories employing satellite imagery and high-precision geochronology used in studies of the Bibliography of Volcanology and basin analysis frameworks from the International Association of Volcanology and Chemistry of the Earth's Interior. Ongoing projects focus on paleoclimate proxies, mineral exploration, and seismic imaging in collaboration with universities such as University of California, Berkeley, Peking University, and University of Oxford.

Category:Volcanic complexes