10 research outputs found

    Vegetation responses to abrupt climatic changes during the Last Interglacial Complex (Marine Isotope Stage 5) at Tenaghi Philippon, NE Greece

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    The discovery that climate variability during the Last Glacial shifted rapidly between climate states has intensified efforts to understand the distribution, timing and impact of abrupt climate change under a wide range of boundary conditions. In contribution to this, we investigate the nature of abrupt environmental changes in terrestrial settings of the Mediterranean region during the Last Interglacial Complex (Marine Isotope Stage [MIS] 5) and explore the relationships of these changes to high-latitude climate events. We present a new, temporally highly resolved (mean: 170 years) pollen record for the Last Interglacial Complex from Tenaghi Philippon, north-east Greece. The new pollen record, which spans the interval from 130,000 to 65,000 years ago, forms part of an exceptionally long polleniferous sediment archive covering the last 1.35 million years. The pollen data reveal an interglacial followed by alternating forest and steppe phases representing the interstadials and stadials of the Early Glacial. Superimposed on these millennial-scale changes is evidence of persistent sub-millennial-scale variability. We identify ten high-amplitude abrupt events in the pollen record, characterised by rapid contractions of closed forest to open steppe environment and interpreted to indicate major changes in moisture availability and temperature. The contractions in forest cover on millennial timescales appear associated with cooling events in the Mediterranean Sea, North Atlantic and Greenland regions, linked to the Dansgaard-Oeschger (DO) cycles of the Early Glacial. On sub-millennial timescales, the pattern of changes in forest cover at Tenaghi Philippon display a structure similar to the pattern of short-lived precursor and rebound-type events detected in the Greenland ice-core record. Our findings indicate that persistent, high-amplitude environmental variability occurred throughout the Early Glacial, on both millennial and submillennial timescales. Furthermore, the similarity of the pattern of change between Tenaghi Philippon and Greenland on sub-millennial timescales suggests that teleconnections between the high-latitudes and the Mediterranean region operate on sub-millennial timescales and that some terrestrial archives, such as Tenaghi Philippon, are particularly sensitive recorders of these abrupt climate changes

    Uplift and slip rates of the eastern Eliki fault segment, Gulf of Corinth, Greece, inferred from Holocene and Pleistocene terraces

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    Uplifted Pleistocene and Holocene marine and fluvial deposits are preserved in the footwall of the Eliki fault, western Gulf of the Corinth, where geodetic extension rates exceed 10 mm a-1. Up to 10 Pleistocene terraces are distinguished in the footwall block of the eastern Eliki fault segment, discontinuously preserved along strike. Terraces are depositional, forming by the progradation of clastic fan deltas, or predominantly erosional, between fan deltas. Correlation of terrace profiles with Late Pleistocene eustatic sea level suggests an uplift rate of c. 1 mm a-1, with an alternative of c. 1.5 mm a-1. On average, higher rates are obtained from uplifted Holocene deposits (c. 1–2 mm a-1). To determine slip rates, a long-term ratio of uplift to subsidence of c. 1:2–3.2, derived from net footwall altitude and basin subsidence–fill and a fault dip of 50° are applied to uplift of c. 1 mm a-1. These produce a slip rate of c. 4–7 mm a-1 contributing c. 2–4 mm a-1 to extension across the Gulf, significantly less than geodetic rates. This discrepancy may result from strain taken up on faults to the north and offshore. Uplift rates decrease little at the Eliki fault tips. Uplift rates are broadly consistent in the central–western Gulf but show a decrease in average uplift from Corinth eastward

    Fault architecture, basin structure and evolution of the Gulf of Corinth Rift, central Greece

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    The style of extension and strain distribution during the early stages of intra-continental rifting is important for understanding rift-margin development and can provide constraints for lithospheric deformation mechanisms. The Corinth rift in central Greece is one of the few rifts to have experienced a short extensional history without subsequent overprinting. We synthesise existing seismic reflection data throughout the active offshore Gulf of Corinth Basin to investigate fault activity history and the spatio-temporal evolution of the basin, producing for the first time basement depth and syn-rift sediment isopachs throughout the offshore rift. A major basin-wide unconformity surface with an age estimated from sea-level cycles at ca. 0.4Ma separates distinct seismic stratigraphic units. Assuming that sedimentation rates are on average consistent, the present rift formed at 1^2Ma, with no clear evidence for along-strike propagation of the rift axis. The rift has undergone major changes in relative fault activity and basin geometry during its short history. The basement depth is greatest in the central rift (maximum 3 km) and decreases to the east and west. In detail however, two separated depocentres 20^50 km long were created controlled by N- and S-dipping faults before 0.4Ma, while since ca. 0.4Ma a single depocentre (80 km long) has been controlled by several connected N-dipping faults, with maximum subsidence focused between the two older depocentres. Thus isolated but nearby faults can persist for timescales ca.1Ma and form major basins before becoming linked. There is a general evolution towards a dominance of N-dipping faults; however, in the western Gulf strain is distributed across several active N- and S-dipping faults throughout rift history, producing a more complex basin geometry

    Corinth Rift margin uplift: new evidence from Late Quaternary marine shorelines

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    New evidence for uplift of the southern margin to the Corinth rift, one of the world's most rapidly extending continental regions, defines an area of uniform uplift separating a more rapidly uplifting western rift flank from a slowly backtilting eastern flank. This major tectonic boundary coincides with geophysical evidence for a junction between flat underlying subducted oceanic plate and steep subduction. We propose that trench rollback by the Anatolian plate over the subducting African plate has led to differential uplift and possible migration of active faulting at the southern rift margin in the last few million years

    Building up or out? Disparate sequence architectures along an active rift margin-Corinth rift, Greece

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    Early Pleistocene synrift deltas developed along the southern Corinth rift margin were deposited in a single, dominantly lacustrine depocenter and were subject to the same climate-related base-level and sediment supply cyclicity. Two synrift deltas, just 50 km apart, show markedly different sequence geometry and evolution related to their location along the evolving border fault. In the west, strongly aggradational fan deltas (>600 m thick; 2-4 km radius) deposited in the immediate hanging wall of the active border fault comprise stacked 30-100 m thick stratal units bounded by flooding surfaces. Each unit evolves from aggradational to progradational with no evidence for abrupt subaerial exposure or fluvial incision. In contrast, in the central rift, the border fault propagated upward into an already deep lacustrine environment, locating rift-margin deltas 15 km into the footwall. The deltas here have a radius of > 9 km and comprise northward downstepping and offlapping units, 50-200 m thick, that unconformably overlie older synrift sediments and are themselves incised. The key factors driving the marked variation in sequence stratigraphic architecture are: (1) differential uplift and subsidence related to position with respect to the border fault system, and (2) inherited topography that influenced shoreline position and offshore bathymetry. Our work illustrates that stratal units and their bounding surfaces may have only local (<10 km) extent, highlighting the uncertainty involved in assigning chronostratigraphic significance to systems tracts and in calculating base-level changes from stratigraphy where marked spatial variations in uplift and subsidence occur. © 2017 Geological Society of America
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