Ultra-High-Resolution Marine 2D-3D Seismic Investigation of the Liman Tepe/Karantina Island Archaeological Site (Urla/Turkey)

Cataloged from PDF version of article.2D and 3D high-resolution seismic investigations were performed on submerged coastal archaeological sites at Iskele and near to Karantina Island in the Bay of Izmir in western Turkey. Tectonic subsidence of the coastline has submerged a number of archaeological features associated with an important Early Bronze Archaic settlement (Liman Tepe) and the classical Ionian city of Clazomenae. Seismic surveys were focused on imaging of an Archaic harbour structure and other submerged Hellenistic and Roman architectural features. Seismic data were acquired with the SEAMAP-3D ultra-high-resolution 3D marine seismic acquisition system developed for detailed archaeological site investigation. A 2D reconnaissance survey was performed over a 2 km2 area around Karantina Island to evaluate the seismic penetrability and to locate sites for further 3D investigation. This survey predominantly revealed marine sediment layers covering the local bedrock, which is characterized by scattering of seismic energy showing its rocky nature. Two ultra-high-resolution 3D seismic surveys were performed. The first covered a 350 m × 30 m area in the modern harbour targeting a prominent Archaic harbour structure. The second was acquired across a 120 m × 40 m area on the southeast shore of the Karantina Island close to a Roman architectural feature. The 3D surveys were acquired with nominal line spacings of 1 m, using a 8× 4 pseudo-rigid hydrophone array and a Boomer source firing at 3 Hz shot frequency. Automated processing of the seismic data using a portable Linux cluster provided stacked 3D seismic volumes with 25 cm × 25 cm bin size on-site. The 3D seismic survey of the harbour clearly imaged the submerged Archaic structure and the underlying sediment sequence. The seismic time slices reveal two seismic anomalies (2–3 m in diameter) in the harbour basin sediments. The 3D surveys southeast of Karantina identified a thicker marine sediment sequence overlying steeply dipping bedrock reflectors. The sediment sequence records the rapid accumulation and progradation of the coastline following the construction the Alexander causeway linking the mainland with the island in 334 B.C

Ultra-high-resolution marine 2D-3D seismic investigation of the Liman Tepe/Karantina Island archaeological site (Urla/Turkey)

2D and 3D high-resolution seismic investigations were performed on submerged coastal archaeological sites at Iskele and near to Karantina Island in the Bay of Izmir in western Turkey. Tectonic subsidence of the coastline has submerged a number of archaeological features associated with an important Early Bronze Archaic settlement (Liman Tepe) and the classical Ionian city of Clazomenae. Seismic surveys were focused on imaging of an Archaic harbour structure and other submerged Hellenistic and Roman architectural features. Seismic data were acquired with the SEAMAP-3D ultra-high-resolution 3D marine seismic acquisition system developed for detailed archaeological site investigation. A 2D reconnaissance survey was performed over a 2 km2 area around Karantina Island to evaluate the seismic penetrability and to locate sites for further 3D investigation. This survey predominantly revealed marine sediment layers covering the local bedrock, which is characterized by scattering of seismic energy showing its rocky nature. Two ultra-high-resolution 3D seismic surveys were performed. The first covered a 350 m × 30 m area in the modern harbour targeting a prominent Archaic harbour structure. The second was acquired across a 120 m × 40 m area on the southeast shore of the Karantina Island close to a Roman architectural feature. The 3D surveys were acquired with nominal line spacings of 1 m, using a 8 × 4 pseudo-rigid hydrophone array and a Boomer source firing at 3 Hz shot frequency. Automated processing of the seismic data using a portable Linux cluster provided stacked 3D seismic volumes with 25 cm × 25 cm bin size on-site. The 3D seismic survey of the harbour clearly imaged the submerged Archaic structure and the underlying sediment sequence. The seismic time slices reveal two seismic anomalies (2-3 m in diameter) in the harbour basin sediments. The 3D surveys southeast of Karantina identified a thicker marine sediment sequence overlying steeply dipping bedrock reflectors. The sediment sequence records the rapid accumulation and progradation of the coastline following the construction the Alexander causeway linking the mainland with the island in 334 B.C. © 2008 Elsevier B.V. All rights reserved

Estimates of Methane Release From Gas Seeps at the Southern Hikurangi Margin, New Zealand

The highest concentration of cold seep sites worldwide has been observed along convergent margins, where fluid migration through sedimentary sequences is enhanced by tectonic deformation and dewatering of marine sediments. In these regions, gas seeps support thriving chemosynthetic ecosystems increasing productivity and biodiversity along the margin. In this paper, we combine seismic reflection, multibeam and split-beam hydroacoustic data to identify, map and characterize five known sites of active gas seepage. The study area, on the southern Hikurangi Margin off the North Island of Aotearoa/New Zealand, is a well-established gas hydrate province and has widespread evidence for methane seepage. The combination of seismic and hydroacoustic data enable us to investigate the geological structures underlying the seep sites, the origin of the gas in the subsurface and the associated distribution of gas flares emanating from the seabed. Using multi-frequency split-beam echosounder (EK60) data we constrain the volume of gas released at the targeted seep sites that lie between 1,110 and 2,060 m deep. We estimate the total deep-water seeps in the study area emission between 8.66 and 27.21 × 10 6 kg of methane gas per year. Moreover, we extrpolate methane fluxes for the whole Hikurangi Margin based on an existing gas seep database, that range between 2.77 × 10 8 and 9.32 × 10 8 kg of methane released each year. These estimates can result in a potential decrease of regional pH of 0.015–0.166 relative to the background value of 7.962. This study provides the most quantitative assessment to date of total methane release on the Hikurangi Margin. The results have implications for understanding what drives variation in seafloor biological communities and ocean biogeochemistry in subduction margin cold seep sites

An Iterated Four-Player Prisoner�s Dilemma Game with an External Selecting Agent: A Metacontingency Experiment

In these series of experiments we used an iterated prisoners� dilemma game (IPDG) to examine the effect of metacontingencies on aggregate products of the interrelated behavior of four players. Results of the first experiment showed that cultural level consequences (�market feedback� in the form of points delivered to all players) contingent on aggregate products XXXX or YYYY increased the frequency of those productions. In subsequent experiments we added a baseline condition where the players experienced only the individual behavioral contingencies embedded in the game. Then we imposed the metacontingency on the XXXX aggregate product or, alternatively, on YYYY. After several reversals, we discontinued the metacontingency and the players again experienced only the individual contingencies of the game. In one experiment we used a yoked control to assess the effect of market feedback independent from the metacontingency relation. Results indicate that the cultural consequence (market feedback) controlled production of aggregate products even when its magnitude was minimal, that the metacontingency relation was necessary, and that it maintained relations among the behavior of individuals which resulted in the worst individual outcomes for all players.En esta serie de experimentos utilizamos un juego iterativo del �Dilema del Prisionero� (IPDG por sus siglas en inglés) para examinar el efecto de las metacontingencias sobre los productos agregados del comportamiento interrelacionado de cuatro jugadores. Los resultados del primer experimento muestran que las consecuencias de nivel cultural (�retroalimentación del mercado� en la forma de puntos entregados a todos los jugadores), contingentes con los productos agregados XXX o YYYY aumentaron la frecuencia de esas producciones. En experimentos posteriores, añadimos una condición de línea de base en la cual los jugadores experimentaron solo las contingencias conductuales individuales incorporadas en el juego. Luego impusimos la metacontingencia sobre el producto agregado XXXX, o de forma alternativa sobre YYYY. Después de varias reversiones, descontinuamos la metacontingencia y los jugadores comenzaron a experimentar nuevamente solo las contingencias individuales del juego. En un experimento utilizamos un control para evaluar el efecto de la retroalimentación del mercado de manera independiente de la relación metacontingencial. Los resultados indican que la consecuencia cultural (retroalimentación del mercado) controló la producción de productos agregados incluso cuando su magnitud era mínima, que la relación metacontingencial era necesaria, y que mantenía relaciones en el comportamiento de los individuos que tenían los peores resultados para todos los jugadores

Effect of Resource Scarcity on Dyadic Fitness in a Simulation of Two-Hunter Nomoclones

Two experiments were conducted in a college where students in dyads participated in a simulation of hunters who were required to share prey in order to maintain dyadic (group) fitness. The sharing was an interlocking behavioral contingency contributing to survival of the dyad, conceptualized as a hunting nomoclone (Harris, 1964). The simulation comprised 6 consecutive hunting seasons in which the antecedent variable of prey scarcity was manipulated as the independent variable. Results of the first experiment did not show a difference in dyadic fitness as a function of prey scarcity. In the second experiment the difference between poor and rich conditions was increased. In rich conditions, all the dyads performed similarly to those in the first experiment. However, in successive poor conditions, dyads started out less fit and became increasingly fit. Thus, sharing IBCs were more difficult to form under significant scarcity, but they became more frequent over time. The experiment is discussed in the context of Skinner�s view (1981) about cultures evolution, Harris�s (1964) taxonomy of cultural things, and Glenn�s (1988, 2004) formulation of metacontingencies.Se condujeron dos experimentos en una Universidad en la cual díadas de estudiantes participaron en una simulación de cazadores que debían compartir su presa para mantener la adaptabilidad diádica (grupal). El compartir era una contingencia conductual entrelazada que contribuía a la supervivencia de la díada, conceptualizada como un nomoclón de cacería (Harris, 1964). La simulación incluyó seis temporadas de caza consecutivas en las cuales la variable antecedente de la escasez de presas fue manipulada como variable independiente. Los resultados del primer experimento no mostraron diferencias en la adaptabilidad diádica como función de la escasez de presas. En el segundo experimento, la diferencia entre condiciones de pobreza y riqueza se aumentó. En las condiciones de riqueza, todas las díadas se desempeñaron de forma similar a las del primer experimento. Sin embargo, en las condiciones de sucesiva pobreza, las díadas comenzaron menos adaptadas pero aumentaron su adaptabilidad progresivamente. De este modo, compartir contingencias entrelazadas fue más difícil en condiciones menos significativas de escasez, pero las mismas se hicieron más frecuentes con el tiempo. El experimento se discute a la luz de la visión de Skinner (1981) sobre la evolución cultural, la taxonomía de cosas culturales de Harris (1964) y la formulación de metacontingencias de Glenn (1988, 2004)

Subducted sediments, upper-plate deformation and dewatering at New Zealand's southern Hikurangi subduction margin

Highlights • Seismic depth imaging gives insight into the southern Hikurangi subduction zone. • Velocities reveal regional variations in compaction and drainage of input sediments. • Dewatering of subducted sediments might influence décollement strength. • Thrusts at the leading edge of deformation are upper-plate dewatering pathways. • Stratigraphic host of the décollement changes at the southern end of the margin. Abstract The southern end of New Zealand's Hikurangi subduction margin accommodates highly oblique convergence between the Pacific and Australian plates. We carry out two-dimensional (2D) seismic reflection tomography and pre-stack depth migrations on two seismic lines to gain insight into the nature of subducted sediments and upper plate faulting and dewatering at the toe of the wedge. We also investigate the NE to SW evolution of emergent upper plate thrust faulting using 47 seismic lines spanning an along-strike distance of ∼270 km. The upper sequence of sediments that ultimately gets subducted (the MES sequence) has an anomalously-low seismic velocity character. At the southwestern end of the margin, ∼150 km east of Kaikōura, the MES sequence has experienced greater compaction (for an equivalent effective vertical stress) than it has some 200 km further to the northeast. This difference is likely attributable to greater horizontal compression in the southwest caused by impingement of the Chatham Rise on the deformation front. Relationships between velocity and effective vertical stress suggest that the MES sequence is well-drained in the vicinity of frontal thrusts, corroborated by evidence for upper plate dewatering along those thrusts. Effective drainage of the MES sequence likely promotes interplate coupling on the southern Hikurangi margin. The décollement is generally hosted near a seismic reflector known as “Reflector 7”. East of Kaikōura, however, Reflector 7 becomes accreted, indicating that subduction slip at the southwestern end of the margin is no longer hosted at (or above) this reflector. Instead, the décollement steps down to a deeper stratigraphic level further inboard. Further to the SW, approximately in line with the lower Kaikōura Canyon, the offshore manifestation of subduction-driven compression ceases

Upward‐Doming Zones of Gas Hydrate and Free Gas at the Bases of Gas Chimneys, New Zealand's Hikurangi Margin

Focused gas migration through the gas hydrate stability zone in vertical gas conduits is a global phenomenon. The process can lead to concentrated gas hydrate formation and seafloor gas seepage, which influences seafloor biodiversity and ocean biogeochemistry. However, much is unknown about how gas and gas hydrate co‐exist within and around gas conduits. We present seismic imaging of the gas hydrate system beneath a four‐way closure anticlinal ridge at New Zealand's southern Hikurangi subduction margin. Gas has accumulated beneath the base of gas hydrate stability to a thickness of up to ∼240 m, which has ultimately led to hydraulic fracturing and propagation of a vertical gas conduit to the seafloor. Despite the existence of an array of normal faults beneath the ridge, these structures are not exploited as long‐range gas flow conduits. Directly beneath the conduit, and extending upward from the regional base of gas hydrate stability, is a broad zone characterized by both negative‐ and positive‐polarity reflections. We interpret this zone as a volume of sediment hosting both gas hydrate and free gas, that developed due to partial gas trapping beneath a mass transport deposit. Similar highly reflective zones have been identified at the bases of other gas conduits, but they are not intrinsic to all gas conduits through gas hydrate systems. We suggest that pronounced intervening sealing units within the gas hydrate stability zone determine whether or not they form.Plain Language Summary: Gas hydrates are ice‐like substances composed of natural gas and water. They form between sediment grains underneath large regions of the Earth's seafloor. An important reason to study gas hydrates is that they partly control the way that methane gas flows through sediments and out of the seafloor. It is this flow of methane that sustains some diverse biological communities on the seafloor and affects the chemistry of the oceans. In this study, we use reflected sound waves to explore how gas flow beneath the seafloor depends on the way in which sedimentary layers are folded and fractured. Our data reveal a 240‐m thick reservoir of gas that is trapped in a large sedimentary fold, ∼500 m beneath the seafloor. The buoyancy of the gas has caused a vertical fracture zone to propagate upward to the seafloor, where gas bubbles are venting into the ocean. Further, our data suggest that a broad accumulation of gas hydrates (together with gas) has formed beneath the vertical fracture zone. This gas hydrate deposit may grow larger with time, and it will continue to influence the way that gas flows through the sediments.Key Points: 240 m thick free gas column accumulated beneath the base of hydrate stability, which led to hydraulic fracturing and gas chimney formation. Broad zone of free gas and gas hydrate formed beneath the gas chimney, extending upward from the regional base of hydrate stability. Such zones of hydrate and free gas likely form due to pronounced lithological contrasts (sealing layers) within the hydrate stability zone.New Zealand's Ministry for Business Innovation and Employment (MBIE) http://dx.doi.org/10.13039/50110000462