Flight Of Terraces Research Articles

Evaluating variability in coseismic slips of paleoearthquakes from an incomplete slip history: an example from displaced terrace flights across the Kamishiro fault, central Japan

Examining the regularity in slip over seismic cycles leads to an understanding of earthquake recurrence and provides the basis for probabilistic seismic hazard assessment. Systematic analysis of three-dimensional paleoseismic trenches and analysis of offset markers along faults reveal slip history. Flights of displaced terraces have also been used to study slips of paleoearthquakes when the number of earthquakes contributing to the observed displacement of a terrace is known. This study presents a Monte Carlo-based approach to estimating slip variability using displaced terraces when a detailed paleoseismic record is not available. First, we mapped fluvial terraces across the Kamishiro fault, which is an intra-plate reverse fault in central Japan, and systematically measured the cumulative dip slip of the mapped terraces. By combining these measurements with the age of the paleoearthquakes, we estimated the amount of dip slip for the penultimate event (PE) and antepenultimate event (APE) to be 1.6 and 3.4 m, respectively. The APE slip was nearly three times larger than the most recent event of 2014 (Mw 6.2): 1.2 m. This suggests that the rupture length of the APE was much longer than that of the 2014 event and the entire Kamishiro fault ruptured with adjacent faults during the APE. Thereafter, we performed the Monte Carlo simulations to explore the possible range of the coefficient of variation for slip per event (COVs). The simulation considered all the possible rupture histories in terms of the number of events and their slip amounts. The resulting COVs typically ranged between 0.3 and 0.54, indicating a large variation in the slip per event of the Kamishiro fault during the last few thousand years. To test the accuracy of our approach, we performed the same simulation to a fault whose slip per event was well constrained. The result showed that the error in the COVs estimate was less than 0.15 in 86% of realizations, which was comparable to the uncertainty in COVs derived from a paleoseismic trenching. Based on the accuracy test, we conclude that the Monte Carlo-based approach should help assess the regularity of earthquakes using an incomplete paleoseismic record.

Edifice of Fluvial Terrace Flights, Stacks and Rows

The paper presents a review of the architecture and structures of river deposits in valleys. A new terminology for some features is included in this review. It presents principles of the fluvial systems with morphological river terraces and fluments (new term for terrace bodies), different stages of the morphological terraces, the texture—the arrangement—of fluments in the form of terrace flights, terrace stacks and terrace rows, and the (inner) structure of a single flument. The contact between the valley fill and the bedrock is named by the new term “pelma”. Special topics deal with flument overlaps and insight into the deepest valley fill down to the bedrock. A comparison with other terms of the fluvial inventory is annexed.

ESR and U-Th dating results for Last Interglacial coral reef terraces at the northern coast of Cuba

Fossil coral reef terraces at the northern coast of Cuba in the vicinity of the Bay of Matanzas are forming a prominent flight of terraces. These terraces were already studied by several investigators, but a chronological classification based on numerical dating is still missing. In this study we focus on the lowest unit, the Seboruco terrace, which is assumed to be of MIS 5e age. The morphology of the Seboruco terrace and associated sea-level markers (reef crests and notches) were mapped and their altitude was measured over the whole study area in the field and by using remote sensing. The fossil corals building up the terrace were surveyed in numerous natural outcrops. The species of the fossil coral reefs were determined and subdivided in different facies zones. Fossil corals were taken for numerical dating by Electron Spin Resonance (ESR) and Uranium-series (U-Th) to establish a chronology of the MIS 5e coral reef formation. Both dating techniques yielded age results in good agreement with each other and the stratigraphic context. Corresponding to the field evidence, the age data indicates one MIS 5e sea-level highstand around 126 ka. Some younger ESR ages may be explained by the recrystallization of aragonitic corals and/or by U leaching. At one locality east of Matanzas, the radiometric results for an underlying coral reef body suggest an MIS 7 age. The sea-level markers for the MIS 5e highstand range from 5.5 m a.s.l. (reef crest) to a maximum of 7 m (notches) west of the Bay of Matanzas resulting in relatively low uplift rates of 0.003 m/ka and 0.036 m/ka when applying early MIS 5e sea-level estimates from tectonically stable coasts in the Caribbean between +2.5 m and +6.6 m. Inside the Bay of Matanzas itself, the elevation of sea-level markers increases to more than 10 m a.s.l. indicating a stronger uplift rate of 0.027 m/ka to 0.060 m/ka here.

A fluvial record of fault-propagation folding along the northern Qilian Shan front, NE Tibetan Plateau

The kinematics of thrust fault is key to understand the deformation and uplift of mountain ranges. Along the northern front of the central Qilian Shan mountain range, the NE Tibet Plateau, a flight of terraces developed along the Red Sand River were deformed above a growing fault-propagation fold. Via luminescence and 10Be exposure dating, abandonment ages of the terrace surfaces were determined to be 100.9 ± 5.8 ka BP for T9, 88.7 ± 7.0 ka BP for T8, and 68.8 ± 7.6 ka BP for T7. Terrace profiles measured by differential GPS across the monocline were used to constrain the recent fold deformation, and the trishear model was applied to estimate the fault slip rate and thrust history. We thus derived an average slip rate of 1.3 ± 0.1 mm/a for the Heihekou (HHK) fault since ~90 ka BP. In addition, our results imply that the onset of the HHK fault occurred at 0.8–1.4 Ma, indicating a recent northeastward propagation of the active thrust faulting of the North Qilian Shan Fault (NQF). Our results also indicate uniformly distributed slip along the western, central, and eastern segments of the north Qilian Shan. Due to the different thrust kinematics along the NQF, the uplift rate is not uniformly distributed along the hanging wall of the thrust.

Morphostratigraphical correlation of river terraces in the central part of the Bohemian Massif with the European stratigraphical classification of the QuaternarY

The results of geomorphological research, focused on identification of larger remains of fluvial terrace sedimentary sequences in the Želivka, Sázava, Berounka, Vltava and Labe river-drainage basins in the Bohemian Massif, are presented. The terrace flights are characterised by a variable structure which is conditioned by the bedrock and drainage-network configuration created prior to the Pleistocene. They are formed by the specific hydrodynamic processes during the Quaternary. A series of transverse-valley profiles and longitudinal profiles have been constructed. This has enabled the differentiation of seven main terrace surfaces underlain by Quaternary fluvial sediments. However, the uppermost levels are underlain by Neogene-age deposits that comprise both fluvial and fluvio-lacustrine sediments at altitudes up to 135 m above the present valley floor. The Quaternary incision of the Sázava and Vltava valleys reaches an average depth of over 100 m. This was induced by neotectonic uplift of the Bohemian Massif. The terrace flights include incised meanders and bends, most of which formed during the Middle Pleistocene. Based on the currently accepted Quaternary chronostratigraphical scheme, the terrace system throughout the Bohemian Massif is mostly of Middle and Late Pleistocene age that is the period from the Cromerian Complex to the Weichselian stages of the NW European scheme. A marked erosional episode, that pre-dates the accumulation of terrace I sediments, occurred at the end of the Early Pleistocene Subseries. Older levels of fluvial sediments in the central part of the Bohemian Massif, occupying higher topographical positions, previously classified as of Pliocene age, are now considered to date from the Early Pleistocene. <b>Morfostratigrafická korelace říčních teras střední části Českého masivu s evropskou stratigrafickou klasifikací kvartéru</b> Říční terasy Želivky, Sázavy, Berounky, Vltavy a Labe mají ve střední části Českého masivu rozmanitou strukturu, která vznikala specifickými morfostrukturními a hydrodynamickými procesy při vývoji údolní sítě v mladším kenozoiku. Geomorfologický výzkum reliktů fluviálních sedimentů v těchto údolích umožnil rozlišit sedm kvartérních akumulačních teras (Tabulka 1) a dvě úrovně fluviálních a fluvio-lakustrinních sedimentů neogenního stáří. Relikty předkvarterních uloženin se vyskytují až 135 m nad současnými dny říčních údolí střední části Českého masivu. Erozivní zahloubení této antecedentní a epigenetické říční sítě bylo podmíněno neotektonickými zdvihy a během kvartéru dosáhlo více než 100 m. Charakteristické zakleslé meandry a ohyby říčních údolí vznikaly převážně ve středním pleistocénu. Podle současného statigrafického členění kvartéru se systém říčních akumulačních teras v údolích střední části Českého masivu vytvořil zejména ve středním a mladém pleistocénu, a to od Cromerského komplexu do Viselského období. Erozní procesy před vznikem říční akumulační terasy I probíhaly koncem staršího pleistocénu. Je také ukázáno, že dynamiku fluviálních procesů je vhodné studovat ve vztahu ke zvětrávání, denudaci, erozi a svahovým pohybům v kvartéru.

Ages and genesis of terrace flights in the middle reaches of the Yarlung Zangbo River, Tibetan Plateau, China

Field investigation has shown that the middle reaches of the Yarlung Zangbo River, in Tibet (known as the Bhramaputra River in reaches downstream) has 11 terraces. The ages of these terraces were determined as follows: T11&gt;2000 ka, T10 = 1783 ka, T9 = 1238 ka, T8 = 683 ka, T7 = 382 ka, T6 = 150 ka, T5 = 82 ka, T4 = 67 ka, T3 = 43 ka, T2 = 28 ka and T1 = 10 ka. These terraces formed during several stages of the Quaternary when the Tibetan Plateau was uplifting, recording tectonic–climatic cycles or subcycles of 1.2, 0.4, 0.1, 0.04 and 0.02 million years duration. The tectonic–climatic cycles identified by this study are correlated with red soil and palaeosol records. The preservation of the Oligocene to Early Miocene conglomeratic Dazhuka Formation, close to the present altitude of the main planation surface of the Tibetan Plateau and occurring only in the Yarlung Zangbo valley, suggests that this river has existed since at least 7 Ma. Discoveries of old and thick fluvial gravel layers extending to within 630 m of the valley floor show that the Yarlung Zangbo River was already incised by 2000 m or more below the surface of the Tibetan Plateau, that much of the incision from plateau to valley floor had been accomplished and that the plateau was already substantially uplifted prior to the Quaternary. In addition to its importance for understanding the evolution of the Tibetan Plateau, this study documents the impact of varying rates of tectonic uplift on river development.

Climate-controlled landscape evolution in the Western Transverse Ranges, California: Insights from Quaternary geochronology of the Saugus Formation and strath terrace flights

The Las Posas and Ojai Valleys, located in the actively deforming Western Transverse Ranges of California, contain well-preserved flights of strath terraces and Quaternary strata (i.e., Saugus Formation) that when numerically dated elucidate the tectonic, geomorphic, and fluvial histories that sculpted the landscape since ca. 140 ka. This study includes 14 new optically stimulated luminescence and 16 new terrestrial cosmogenic nuclide ages from the late Pleistocene to Holocene that record two regional aggradation events and four intervals of strath terrace formation. Geochronologic data indicate that terrestrial Saugus strata in the Las Posas Valley (Camarillo Member) prograded over marine deposits at ca. 125 and 80 ka and are as young as 60–25 ka, which is an order of magnitude younger than the youngest Saugus strata elsewhere in Southern California. These results highlight the need for precise dating of Saugus strata where identified and utilized to assess rates of tectonic deformation. Based on its compositional character, thickness, stratigraphic relations, and inferred ages, the Camarillo member of the Saugus Formation is correlated with sediments of the Mugu aquifer identified in subcrop throughout the Ventura Basin and thus provides a new regional chronostratigraphic subsurface datum. The aggradation of these sediments and similar deposits in the study area between 13 and 4 ka is subsequent to the transition from humid to semiarid climate correlating to the end of the ultimate and penultimate glacial maximums. Aggradation is inferred to have resulted from increased sediment supply in response transient vegetative conditions and consequent hillslope destabilization. Similar to aggradational events, strath terrace cover sediments ages correlate to dry warm climate intervals, indicating straths in Southern California were cut at ca. 110–100 ka, 50–35 ka, 26–20 ka, and 15–4 ka. These results support recent mathematical and experimental models of strath formation, where increased sediment flux and decreased water discharge enhances lateral erosion rates and inhibits vertical incision. Subsequent incision and strath terrace formation is inferred to occur during intervening wet climate intervals. The correlation of strath terrace ages and aggradational events with environmental changes that are linked to global climate indicates that climate rather than tectonics exhibits first-order control of depositional, denudational, and incisional processes in the Western Transverse Ranges. Moreover, these results provide a chronostratigraphic framework that allows these landforms to be regionally correlated and used to assess rates of active tectonics where geochronologic data are unavailable.

The interpretation of progressive fault displacement of flights of terraces

Abstract Progressive movement resulting in displacements that can be resolved into horizontal and vertical components is recorded in the fault–displacement of flights of river terraces, the oldest terraces showing the greatest displacements. No unique interpretation of the sequence of events is possible, as illustrated from a hypothetical example, but the vertical and horizontal components of individual movements can be deduced according to a stated rule. In associating fault movement and river downcutting, the heights of the terraces on the lower side of the fault scarp should be used, not those on the higher side. As a result it is concluded that at the Wairau River downcutting and faulting do not show the linear relation deduced by Wellman; as a preferred interpretation, the rate of faulting is supposed to have been substantially uniform while the rate of downcutting has diminished, since the formation of the highest, depositional, surface in the flight. The depositional surface is typical of the highe...

Evolution of fluvial terraces in response to climate change and tectonic uplift during the Pleistocene: Evidence from Kamienica and Ochotnica River valleys (Polish Outer Carpathians)

Fluvial terraces of Kamienica and Ochotnica River valleys recorded vertical movements of the Earth's crust and oscillatory changes in the Pleistocene climate. Seven terrace levels are present in the valleys, usually built of a bedrock surface overlain by a fluvial sediment cover of various thickness. These flights of terraces formed a staircase-like relief during the cyclical evolution of the valley bottoms. During the interglacial periods, valley bottoms widened and bedrock platforms were formed that later became the base on which fluvial deposits accumulated. The main phases of aggradation took place during the glacial periods and partly also in the interglacials. Incision and deepening of the valleys were mainly confined to the phases of glacial–interglacial transition, additionally also during interglacials and the interglacial–glacial transitions while the area was uplifted constantly throughout the Pleistocene. Results of the research were supported by published studies on simulation and modelling.

Evaluating the role of climate and tectonics during non-steady incision of the Yellow River: evidence from a 1.24 Ma terrace record near Lanzhou, China

The competing roles of bedrock uplift and climatic change in the formation of fluvial terraces remain uncertain. Most of recent studies have attributed terrace formation to climatic changes and held that, even in tectonically active settings, climate variations control cycles of terrace planation and abandonment. Based on field investigations of loess-paleosol sequences, magnetostratigraphy and optically stimulated luminescence (OSL) dating, we develop a new chronology for a spectacular flight of terraces along the Yellow River near Lanzhou, China over past 1.24 Ma. All the terraces are strikingly similar in that they have several meters of paleosol developed directly above fluvial deposits on the terrace treads, suggesting that the abandonment of each terrace due to river incision occurs during the transition from glacial to interglacial climates. However, the ages of terraces cluster in two relatively short time periods (1.24–0.86 Ma and 0.13 Ma – present). During the intervening time between 0.86 Ma and 0.13 Ma, terraces either did not form or were not preserved. We suggest that this record indicates that rock uplift rates varied through time and influenced terrace formation/preservation. Thus, our results demonstrate the utility of deep chronologic records from fluvial terraces for deconvolving the effects of tectonics and climate on fluvial incision.

Geomorphology and tectonics of uplifted coasts: New chronostratigraphical constraints for the Quaternary evolution of Tyrrhenian North Calabria (southern Italy)

The Tyrrhenian coastal sector of North Calabria, stretching between Torre S. Nicola and the Lao river, belongs to the inner extensional sector of the Neogene Apennines thrust belt. It is characterised by a stair of Quaternary marine and fluvial terraces representing the geomorphic response to the interaction between the Quaternary sea level fluctuations and the regional trend of tectonic uplift experienced by the margins of the Tyrrhenian back-arc basin. Since the last century, several authors studied the North Calabria coasts, where the flight of terraces preserves significant marine and continental successions, and proposed several paleo-geomorphological and tectonic reconstructions. In this paper we present a new stratigraphic and morphostructural setting of the North Calabria coasts based on both chronostratigraphical constraints obtained from marine deposits and detailed geomorphological analysis. A ten order stair of marine terraces, stepping between 240 and 0 m a.s.l., was recognized and time-constrained by the age of the Fornaci S. Nicola marine succession which was ascribed by integrated paleoecological, biostratigraphical and paleomagentic analyses to the early Middle Pleistocene (MIS 19–15). In particular, the 240, 200 and 160 m a.s.l. high strandlines were ascribed to the Early Pleistocene and the ones between 100 and 15 m a.s.l. to the Middle Pleistocene. The total amount of the vertical motion experienced by the studied area was estimated, and evaluation of the average rates of uplift for the Middle and Late Pleistocene times were also given. Considering the elevation a.s.l. of the oldest terraces, a tectonic uplift of at least 240 m was calculated for the North Calabria coasts since the Early Pleistocene times, 100 m of which gained from the beginning of the Middle Pleistocene. On the other hand, the 8-m high Late Pleistocene strandlines display a negligible vertical displacement affecting the area during the last 130 ka. The entire staircase of terraces preserves a record of slowing down in the rate of uplift, which attained an average value of 0.15 mm/year during the Middle Pleistocene.

Fluvial networks of the Iberian Peninsula: a chronological framework

Knowledge of the evolution of Spanish fluvial networks has improved during recent years as more river systems have been studied and more geochronological data has become available. However, the chronological framework is a major issue as the range of applications is limited by methodological constraints and spatial coverage is sparse. Integration of ‘absolute’ dating methods with biostratigraphy and palaeomagnetism permits the recent evolution of these river systems to be reviewed. The timing of incision from the Late Neogene to the present varies between the major Iberian fluvial systems, depending on the substrata and tectonic settings. Early Pleistocene and older fluvial sequences in the core areas of the Iberian Peninsula provide a more extensive record of fluvial evolution and are better preserved than the terrace flights in the coastal lowlands. Middle Pleistocene sequences are well developed in most of the major river systems in Iberia, particularly those of the Tajo, Guadalquivir and Aguas River, and frequently represent the principal climatic cycles of that period, although tectonic and sea-level effects can also be seen. For Late Pleistocene to Holocene times, the scheme becomes more complex. Our review suggests that each river system has responded differently to local and regional climate control, glacial and periglacial processes in headwaters in high mountain areas, glacio-eustatic sea-level changes and local and regional tectonic patterns.

Pedogenic approach to resolving the geomorphic evolution of the Pakua river terraces in central Taiwan

The southern part of the Pakua tableland in Taiwan comprises a series of wide, unpaired river terraces that have as many as six altitude levels, from PK-1 (highest) to PK-6 (lowest). The terrace surfaces are covered with lateritic soils. This study described, sampled and analyzed the soils from each terrace. Soil taxonomies are Oxisol, Ultisol and Inceptisol . Soil morphological characteristics were quantified as a profile development index (PDI) to determine the degree of soil development. The chemical analyses included cation exchange capacity (CEC) and selected extraction of Fe in soils. Based on the degree of soil development, surface deposits on terrace flights form the post-incisive soil chronosequence, supporting the hypothesis of terrace formation by fluvial processes. Soil ages were estimated based on iron crystallinity (Fe d–Fe o)/Fe t. Analytical results indicate that river terraces in the Pakua tableland are aged 40–400 ka. The long-term uplift rate of the tableland can be estimated using terrace ages and folding geometry. The variation of uplift rates demonstrates that the landscape underwent increased shortening of frontal thrusting by the Changhua Fault running beneath the tableland.

Active structures as deduced from geomorphic features: a case in Hsinchu Area, northwestern Taiwan

Two previously documented active faults in northwestern Taiwan, the Hsinchu and Hsincheng Faults, are evaluated for their earthquake hazard potential by using a Digital Elevation Model (DEM), aerial photos and field mapping. Both of these thrust faults contain active anticlines in their hanging walls based on folding of young alluvial deposits. Mapping of the Hsinchu Fault suggests the presence of numerous scarps oriented sub-parallel to the fault trace that was previously defined by projection of subsurface geology. We interpret the geometry of the surface scarps to be mainly produced by the thrust component, but in part by a lateral component of fault slip. The scarps associated with the Hsincheng Fault system are less complex and offset a flight of terraces, including the modern flood plain. A back thrust exposed 1–2 km east of the Hsincheng Fault is interpreted as linked with the main thrust. Surface deformation is only apparent south of the Touchien River, and becomes less obvious across another wrench fault system, which is linked to Hsinchu Fault in the west and extends southeastward, parallel to the Touchien River. The wrench fault system mentioned above not only offsets the Hsinchu Fault, but also divides the Hsincheng Fault into segments. The supporting evidence found for this includes pressure ridges and pull-apart sags. Two associated hanging wall anticlines are both recently active based on deformed geomorphic surfaces. Two major NE striking thrusts and one NW wrench fault system are identified, reflecting the compression stress is partitioned in this area, which might be resulted from recently influenced extension tectonics, i.e., Okinawa back-arc rifting.

Late Quaternary activity of the Feldbiss Fault Zone, Roer Valley Rift System, the Netherlands, based on displaced fluvial terrace fragments

The Meuse River crosses the Feldbiss Fault Zone, one of the main border fault zones of the Roer Valley Graben in the southern part of the Netherlands. Uplift of the area south of the Feldbiss Fault Zone forced the Meuse River to incise and, as a result, a flight of terraces was formed. Faults of the Feldbiss Fault Zone have displaced the Middle and Late Pleistocene terrace deposits. In this study, an extensive geomorphological survey was carried out to locate the faults of the Feldbiss Fault Zone and to determine the displacement history of terrace deposits. The Feldbiss Fault Zone is characterized by an average displacement rate of 0.041–0.047 mm a −1 during the Late Pleistocene. Individual faults show an average displacement rate ranging between 0.010 and 0.034 mm a −1. The spatial variation in displacement rates along the individual faults reveals a system of overstepping faults. These normal faults developed by reactivation of Paleozoic strike-slip faults. As fault displacements at the bases of the younger terrace deposits are apparently similar to the tops of the adjacent older terrace, the age of these horizons is the same within thousands of years. This implies that the model of terrace development by rapid fluvial incision followed by slow aggradation does apply for this area.

Oxygen-isotope correlation of marine terraces and uplift of the Mesa hills, Santa Barbara, California, USA

Abstract Resolving the chronology of marine terrace sequences is critical for determining uplift rates along tectonically active coastlines. Unfortunately, lack of suitable dating materials often makes this difficult. We present here oxygen isotopic data from 21 shells of Olivella biplicata from four marine terraces in the Santa Barbara and Ventura area located in southern California, USA. Terraces U-series dated at 47 ± 0.5 ka BP at Isla Vista and 70 ± 2 ka BP at Santa Barbara City College (SBCC) provide age control for the isotopic data. Shells from the Isla Vista and SBCC terraces yield average values of 1.117‰ and 0.627‰. respectively, and shells from a non-U-series dated terrace at Punta Gorda and an undated terrace at Santa Barbara Point yield average values of 1.010‰ and 0.751‰, respectively. The data indicate that stable oxygen isotopic signatures preserved in marine terrace molluscs provide a useful tool for correlating undated terraces with those of known age. Furthermore, we are able to correlate samples collected from offset fragments of the Punta Gorda terrace on either side of the Red Mountain fault, demonstrating the utility of this method for correlating terraces across structural features. Using oxygen isotopic data coupled with the U-series dated wave-cut platform at SBCC we calculate a rate of uplift ranging from 0.62 ± 0.03 mm/year (where the elevation of the first emergent terrace is 41 m) to 0.54 ± 0.05 mm/year (where the elevation of the first emergent terrace is 36 m) for marine terrace flights preserved on the Mesa hills anticline located in the city of Santa Barbara, California.

Regional uplift and local tectonic deformation recorded by the Quaternary marine terraces on the Ionian coast of northern Calabria (southern Italy)

The setting of a flight of marine terraces along a 65-km-long section of the Ionian coast of northern Calabria is the result of the interaction between interglacial sea levels, regional uplift, and local fault-related elevation changes. Seven terraces with corresponding palaeoshoreline angles at elevations ranging from 12 m to ∼420 m were recognised by aerial photo interpretation and field surveying. The terraces were correlated to the oxygen isotope stages 1, 5a, 5c, 5e, 7, 9, 15, which correspond to the 7, 81, 102, 124, 215, 330 and ∼600 ka highstands of the palaeosea-level curve. The ∼600-ka-long regional ascent of the terraces took place at an average uplift rate of 0.67 mm/yr; this value slightly but progressively increases southward along the coastline. The elevation of the strandlines is related to the activity of tectonic structures. Three cases were analysed, allowing us: (1) to recognise the height anomalies of the terraces on the Sibari plain as the result of cumulated coseismic deformation caused by the normal Castrovillari fault, and on this basis calculate a minimum slip rate and a mean recurrence time for a single event of deformation; (2) to exclude the presence of significant vertical deformations and consequently activity on the easternmost section of the normal Pollino fault; and (3) to hypothesise the presence of an hitherto unknown active fault responsible for the strong vertical displacements of the flight of terraces near the river Avena. Finally, we find the ratio of the rate of regional uplift to the average rates of local tectonic deformation to be 2 to 3 : 1.

Quaternary evolution of the Corinth Rift and its implications for the Late Cenozoic evolution of the Aegean

SUMMARY We present geological and morphological observations at different scales to constrain rates of faulting and the distribution of deformation in the seismically active Aegean region. We focus first on the 130 km long Corinth Rift, an asymmetric graben where a flight of terraces of marine origin are uplifted. We show that the edges of the terraces lie in the footwall of the normal fault bounding the Corinth Rift and correspond to sea-level highstands of laic Pleistocene age. Using a detailed analysis of aerial and SPOT imagery supported by field observations, we have mapped 10 terrace platforms and strandlines ranging in elevation from 10 to 400 m over distances of 2 to 20 km from the fault. The elevation of the terraces' inner edges was estimated at 172 sites with an error of ±5m. This data set contains a precise description of the uplift and flexure of 10 different palaeohorizontal lines with respect to the present sea level. To date the deformation, we correlate the Corinth terraces with late Pleistocene oxygen-isotope stages of high sea-level stands and with global sea-level fluctuations. Using a thick elastic plate model consistent with our current understanding of the earthquake cycle and a boundary-element technique we reproduce the geometry of the shorelines to constrain both mechanical parameters and the slip on the fault. We show that the seismogenic layer behaves over the long term as if its elastic modulus were reduced by a factor of about 1000. All the terraces are fitted for fault slip increasing in proportion to terrace age, and the component of regional uplift is found to be less than 0.3 mm yr−1. The best fits give a slip rate of 11±3 mm yr−1 on the main rift-bounding fault over the last 350 kyr. Other geological and morphologic information allows us to estimate the total age of the main fault (∼1 Ma) and to examine the mechanical evolution of the Corinth Rift. The minimum observed sediment thickness in the Gulf places an extreme check on the results of the modelling and a lower bound on slip rate of 6–7 mm yr−1 (40 per cent less than estimated with modelling). Even this slip rate is nearly 10 times higher than for comparable features in most of the Aegean and elsewhere in the world. At a larger scale, the spacing and asymmetry of the rift systems in the Aegean suggest strain localization in the upper mantle, with slow extension starting 15 Myr ago or earlier. The more recent (1 Myr), rapid phase of rifting in Corinth partly reactivated this earlier phase of extension. The younger faulting in Corinth appears to result from its present location in the inhomogeneous stress field (process zone) of the south-westward propagating tip of the southern branch of the North Anatolian Fault. We extend these relations to propose a mechanical model for the Late Cenozoic evolution of the Aegean. As the Arabia/Europe collision progressed in eastern Turkey it caused Anatolia to move to the west and the North Anatolian Fault to propagate into the Aegean, where the early slow extension started to be modified about 5 Ma ago. The process of propagation dramatically increased the activity of some but not all of the earlier rifts. The model we present is compatible with tectonic observations, as well as with the seismicity, the palaeomagnetic rotations and the displacement field now observed with GPS and SLR.

River Terraces at the Middle and Lower Course of the Bílina River As an Unifying Element of Ohře and Elbe Terrace Flights

The results of geomorphological analysis of terrace flights at the middle and lower course of the Bílina River are summarized in this article (Bílina merges with the Elbe in Ústí nad Labem). The older terraces (up to the V1 level from Mindel 2) belong to the Ohře River which flowed there until the Middle Pleistocene period. Only the most recent terraces of the groups VI. and VII. were accumulated by Bílina, whose upper course now follows the abandoned Ohře valley. The Ohře terrace flight is compared with the Elbe terrace system.

パプアニューギニア北東部のサンゴ礁段丘の総合研究 無節サンゴモ（紅藻綱）から見たパプアニューギニア，ヒュオン半島の第四紀段丘を構成する石灰岩

The extensive flight of terraces occurs on the northeast seaboard of Huon Peninsula, Papua New Guinea. The terraces consist of many Quaternary reef-complex limestone bodies of different ages.Fossil nonarticulated coralline algal florae were examined in the limestones forming the Pleistocene terraces : II, IIc-lower, IIIc-upper, IIIb, IIIa-lower, IIIa-middle, IIIa-upper and IIIa-upper+ from the coast to the inland area at Kanzarua ; and IV, Vb, Va, Vib, VIa, Mic and VIIb from the coast to the inland area at Kwambu. Depositional environments of these limestones are determined on the basis of comparison with the distribution of coralline algae in the present-day reef complex around Huon Peninsula, the Ryukyu Islands and other Indo-Pacific regions.Nineteen species coming under ten genera of fossil nonarticulated coralline algae have been identified. Two coralline algal assemblages are discriminated. One is characterized by the presence of Porolithon onkodes, and thought to be indicative of shallow forereef environment. This assemblage occurs on II, IIIc-lower, IIIc-upper, IIIb, IIIa-lower, upper and IIIa-upper+ of Kanzarua, and Va, VIIc, VIIb of Kwambu, implying that these terraces correspond to ancient lagoon to reef-core facies. The other is delineated by the presence of Lithothamnion australe associated with Lithothamnion, Sporolithon and Lithophyllum species. This assemblage occurs in rhodoliths of rhodolith floatstone and packstone-wackestone exposed at the cliffs of terrace IV, Vb, Va, VIb and VIa at Kwambu. It can be thought that these fossil rhodoliths were deposited in the deep forereef environment because their constituents are very similar to those of deep water rhodoliths around the Ryukyu Islands. Therefore, each rhodolith-bearing facies of terrace cliff is the deeper counterpart of reef-core facies forming some higher terraces and the antecedent sediments to the formation of its consisting terrace. At Kwambu, terraces IV, Vb, VIb and VIa are composed of the rhodolith-bearing limestones and, these terraces thought to be abrasion platforms on the older, uplifted, deep forereef deposits.