IS THE EASTERN ANATOLIAN HIGH PLATEAU A MODERN ANALOGUE FOR PALEOGENE TRANS-PECOS?

Only two things are certain about the tectonic setting of the Trans-Pecos during the Paleogene: it began under a compressional stress regime that lasted through the Paleocene, as evidenced by fold-and-thrust structures and regressive sedimentary sequences, and it ended under a tensional stress regime that continued through the Miocene, as evidenced by normal faulting. Magmatism was sparse during these earlier and later phases, but was voluminous from the middle Eocene (~48 Ma) to the late Oligocene (~27 Ma) and especially from the late Eocene into the early Oligocene (~38-32 Ma) coincident with the start of the “Great Ignimbrite Flare-Up” that affected much of the southern Cordillera. Magmatism in the Trans-Pecos (collectively assigned to the Trans-Pecos Magmatic Province, TPMP) consists largely of metaluminous to peralkaline trachyte and rhyolite, and has been variably interpreted as the result of either (1) continental rifting and compared with the modern Kenya Rift, or as (2) subduction and compared with modern back-arc settings such as the D’Entrecasteaux Islands, New Guinea, or Mayor Island, New Zealand. Although each of these settings have similarities with the TPMP, none are adequate. Instead, the closest modern analogue to the TPMP may be the Plio-Holocene Eastern Anatolian High Plateau (EAHP), which includes peralkaline systems such as Mount Nemrut—a volcano remarkably similar to the Pine Canyon volcano in terms of both composition and petrogenesis. The EAHP is described as an example of a post-orogenic tectonic environment in which the mantle lithosphere has eroded away and continental crust directly overlies hot asthenospheric mantle as the result of slab roll-back and break-off.