Rapid early-middle Miocene exhumation of the Kazdag Massif (western Anatolia)

Apatite fission-track analyses indicate that the Kazdag. Massif in northwestern Anatolia was exhumed above the apatite partial annealing zone between 20 and 10 Ma (i.e. early-middle Miocene), with a cluster of ages at 17-14 Ma. The structural analysis of low-angle shear zones, high-angle normal faults and strike-slip faults, as well as stratigraphic analysis of upper-plate sedimentary successions and previous radiometric ages, point to a two-stage structural evolution of the massif. The first stage encompassing much of the rapid thermal evolution of the massif-comprised late Oligocene-early Miocene low-angle detachment faulting and the associated development of small supradetachment grabens filled with a mixture of epiclastic, volcaniclastic and volcanic rocks (Kucukkuyu Fm.). The second stage (Plio-Quaternary) has been dominated by (i) strike-slip faulting related to the westward propagation of the North Anatolian fault system and (ii) normal faulting associated with present-day extension. This later stage affected the distribution of fission-track ages but did not have a component of vertical (normal) movement large enough to exhume a new partial annealing zone. The thermochronological data presented here support the notion that Neogene extensional tectonism in the northern Aegean region has been episodic, with accelerated pulses in the early-middle Miocene and Plio-Quaternary

Fission-Track Thermochronology Applied to the Evolution of Passive Continental Margins

International audiencePassive continental margins (PCMs) form at divergent plate boundaries in response to continental breakup and subsequent formation of new oceanic basins. The onshore topography of PCMs is a key component to understand the evolution of extensional settings. The classic nomenclature of PCMs is derived from early investigations that suggested apparent tectonic stability after the initial phase of rifting and breakup. However, geological and geomorphic diversity of PCMs requires more complex models of rift and post-rift evolution. Fission-track (FT) thermochronology provides appropriate tools to decipher the long-term development of PCM topography and better resolve the spatial and temporal relationships between continental erosion and sediment accumulation in adjacent offshore basins. FT datasets have revealed complex spatial and temporal denudation histories across some PCMs and have shown that several kilometres of material may be removed from the onshore margin following rifting. Combining these data with geological and geomorphological observations, and with predictions from numerical modelling, suggests that PCMs may have experienced significant post-rift activity. Case histories illustrated in this chapter include the PCM of southeastern Africa and the conjugate PCMs of the North and South Atlantic