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The fill of trench-slope basins is complex, varying temporally, laterally, and longitudinally. New data from the Neogene stratigraphy of the Akitio Sub-basin, Wairarapa, are presented to investigate such fill variation. The preserved basin fill spans an area 70 km long by 10 km wide, representing deposits from a trench-slope basin. Integration of sedimentological, micropalaeoentological, and geological mapping data charts basin fill evolution. Over 15 km of strata were logged, defining 17 lithofacies associations, which were mapped across the basin; these are interpreted to represent both shallow and deep-water environments. The deep-water strata show a temporal evolution from ponded turbidite deposition, to a period of basin spill via conduits connecting to downstream basins, development of aggradational channel-levees, and finally unconfined submarine fan deposition. Shallow marine deposits mostly developed on the up-dip basin margin occur contemporaneously with basinal mass-transport deposits, and in association with the growth of basin bounding structural ridges. Comparison with the evolution of the offshore, actively filling Akitio Trough highlights controls on trench-slope basin fill: a first-order influence of external controls, e.g. tectonism to create the basin; a second-order progression from under- to overfilled; and third-order lateral variation reflecting autogenic process and the effects of local structures on seafloor gradients. These factors combine to vary sedimentation in trench-slope-basins spatially and temporally. [ABSTRACT FROM AUTHOR]

The North Anatolian Fault Zone ( NAFZ) is one of the most hazardous active faults on Earth, yet its Pliocene space-time propagation across the north Aegean domain remains poorly constrained. We use low-temperature multi-thermochronology and inverse thermal modelling to quantify the cooling history of the upper crust across the Olympus range. This range is located in the footwall of a system of normal faults traditionally interpreted as resulting from superposed Middle-Late Miocene N-S stretching, related to the back-arc extension of the Hellenic subduction zone, and a Pliocene-Quaternary transtensional field, attributed to the south-westward propagation of the NAFZ. We find that accelerated exhumational cooling occurred between 12 and 6 Ma at rates of 15-35 °C Ma−1 and decreased to <3 °C Ma−1 by 8-6 Ma. The absence of significant Plio-Pleistocene cooling across Olympus suggests that crustal exhumation there is driven by late Miocene back-arc extension, while the impact of the NAFZ remains limited. [ABSTRACT FROM AUTHOR]

Abstract: Detailed analysis of the stratigraphic architecture and deformation of lower trench-slope sedimentary basins permits the tectonic evolution of subduction margins to be constrained. This study utilises offshore seismic reflection profiles and onshore outcrop data to examine the entire lower trench-slope of the Hikurangi subduction margin in the eastern North Island, New Zealand. Our results constrain the main spatial and temporal changes of facies and sedimentary units since about 25Ma. We demonstrate that the geometries and locations of Miocene to Quaternary sedimentary basins are controlled by tectonic activity and reflect stages of subduction wedge development. Four types of sedimentary basins have been recognized: 1) flysch basins with local olistostromes at the front of seaward propagating thrust sheets; 2) 5–10km wide turbidite-rich trench-slope basins between uplifting structural ridges (i.e. anticlines) associated with shortening within 100km of the subduction front at the seafloor; 3) 30–40km wide trench-slope basins associated with an upslope increase in thrust and ridge spacing; and 4) mixed siliciclastic-carbonate shelves formed in association with margin uplift after filling of the wider (30–40km) trench-slope basins. The lateral and vertical successions of basin geometries and sedimentary infill are consistent with the overall progressive uplift of the subduction wedge. Formation of some of the wide trench-slope basins may be accompanied by significant local subsidence and normal faulting synchronous with active shortening at the subduction front. Margin-wide normal faulting during the Middle–Late Miocene may have formed due to upslope collapse related to tectonic erosion. All of the basins studied contain major unconformities at their base and top, with basin strata deposited over about 2–8Myr. The short life span of these lower trench-slope sedimentary basins is consistent with a succession of short paroxysmal tectonic episodes rather than continuous deformation for the duration of subduction. Stratigraphic discontinuities within basins (e.g., facies changes and reversal of paleo-currents) also record short-term tectonic events (c. 1–2Myr) on the basin-bounding structures and attest to the episodic nature of upper-plate deformation in response to continuous subduction beneath the active margin. [Copyright &y& Elsevier]

The forearc of the North-Central Peruvian Andes (FNCPA, 6–10°S) provides an exceptional opportunity to study the long-term processes that affect a convergent plate boundary. First, it shows long-term subsidence, depocenter superimposition and individualization. Second, although being mostly extensional and characterized as a typical erosive margin, the FNCPA shows complex uplifted regions. Older deformation is expressed by basement horst and grabens disposed in a complex geometry which onset may have resulted from strike-slip tectonics. A long-lived episode of regional subsidence affected the forearc and led to the relatively thick and regional deposition of the lower Miocene series coeval with a significant increase of the convergence velocity. This period was followed by an episodic uplift of trench-parallel corridors along the so-called Main Deformation Zone. Uplift ceased through the late Miocene and restarted during Pliocene and Quaternary, generating accommodation space by basin flank uplift for a forearc depocenter characterized by landward tilted strata. Significant along-strike differences in the degree of uplift resulted in either uplifting series producing sharp seaward dipping erosional surfaces or less uplifted areas covered by seawards prograding clinoforms. As a consequence of the shallow-water marine setting, the seismic strata geometry, lateral extent and thickness of the deposits for the Neogene successions in the FNCPA have been also tightly controlled by accommodation changes. Uplift is uneven along-strike independently of fault direction and closely followed the increase of the subsidence of the continental slope produced by subduction-erosion. Therefore, sediment underplating seems the most appropriate mechanism at the origin of uplift; as observed in other parts of the Peruvian and Chilean margins. Although the erosive character of the margin, the effects on basin geometry of the raised zone resemble that of typical outer forearc highs in accretionary margins such as in the Kumano basin in Japan. • Transtensional depocenters resulted from high obliquity convergence during the Paleogene. • A trench-parallel uplift affected unevenly and episodically the transtensional depocenters since middle Miocene. • Formation of an outer forearc high, similar to those of accretionary settings, individualized a depocenter during Neogene. • Formation of the outer forearc high may have been induced by sediment underplating. [ABSTRACT FROM AUTHOR]