Rhodes Basin Research Articles

Miocene to Quaternary geodynamic evolution of the southern section of the Burdur-Fethiye Shear Zone and its offshore continuation, eastern Mediterranean

The main interrelated structures of the eastern Mediterranean are shaped by the complex tectonic regimes including active subduction, uplift, and progressive counterclockwise rotation. The Hellenic Arc, the Anaximander Mountains, the Western Taurides, the extensional western Anatolian graben, the Burdur-Fethiye Shear Zone and the Rhodes Basin are these structures located in one of the most tectonically active regions. The Burdur-Fethiye Shear Zone is a 75- to 90- km wide and 300-km-long transtensional left-lateral shear zone developed during the formation of the Aegean back-arc extensional system and the thrusting of Western Taurides. In this study, fault kinematic analysis, and DEM and earthquake data characterize the tectonic controls of the southern section of the Burdur-Fethiye Shear Zone. The high-quality multibeam bathymetry data, their processing and interpretation with the onshore structures and an integrated interpretation with multichannel seismic profiles allowed the geodynamic evolution of the Burdur-Fethiye Shear Zone, Rhodes Basin and environs to be evaluated. Despite the heated debates regarding the presence of the zone, the latest offshore data reveals again that the continuation of the subduction transform edge propagator (STEP) fault between the Hellenic and Cyprus arcs comes into play as the Burdur-Fethiye Shear Zone on land.

A reappraisal of active tectonics along the Fethiye–Burdur trend, southwestern Turkey

SUMMARYWe investigate active tectonics in southwestern Turkey along the trend between Fethiye, near the eastern end of the Hellenic subduction zone, and Burdur, on the Anatolian plateau. Previously, regional GNSS velocities have been used to propose either (1) a NE-trending zone of strike-slip faulting coined the Fethiye–Burdur Fault Zone, or (2) a mix of uniaxial and radial extension accommodated by normal faults with diverse orientations. We test these models against the available earthquake data, updated in light of recent earthquakes at Arıcılar (24 November 2017, Mw 5.3), Acıpayam (20 March 2019, Mw 5.6) and Bozkurt (8 August 2019, Mw 5.9), the largest in this region in the last two decades. Using Sentinel-1 InSAR and seismic waveforms and arrival times, we show that the Arıcılar, Acıpayam and Bozkurt earthquakes were partially or fully buried ruptures on pure normal faults with subtle or indistinct topographic expressions. By exploiting ray paths shared with these well-recorded modern events, we relocate earlier instrumental seismicity throughout southwestern Turkey and incorporate these improved hypocentres in an updated focal mechanism compilation. The southwestern Fethiye–Burdur trend is dominated by ESE–WNW trending normal faulting, even though most faults evident in the topography strike NE–SW. This hints at a recent change in regional strain, perhaps related to eastward propagation of the Gökova graben into the area or to rapid subsidence of the Rhodes basin. The northeastern Fethiye–Burdur trend is characterized by orthogonal normal faulting, consistent with radial extension and likely responsible for the distinct physiography of Turkey’s Lake District. We find that the 1971 Mw 6.0 Burdur earthquake likely ruptured a NW-dipping normal fault in an area of indistinct geomorphology near Salda Lake, contradicting earlier studies that place it on well-expressed faults bounding the Burdur basin, and further highlighting how damaging earthquakes are possible on faults that would prove difficult to identify beforehand. Overall, our results support GNSS-derived kinematic models that depict a mix of uniaxial and radial extension throughout southwestern Turkey, with no evidence from focal mechanisms for major, active strike-slip faults anywhere along the Fethiye–Burdur trend. Normal faulting orientations are consistent with a stress field driven primarily by contrasts in gravitational potential energy between the elevated Anatolian plateau and the low-lying Rhodes and Antalya basins.

The Anatolian Diagonal: a broad left lateral shear zone between the North Anatolian Fault Zone and the Aegean / Cyprus Arcs

Recent detailed examination of the internal deformation of the Turkish-Iranian Plateau in the hinterland of Bitlis-Zagros Suture Zone, which is related to the collision of the Arabian and Eurasian plates, indicates multiple intersection points between the right- and left-lateral strike-slip structures explained by an inevitably broad left-lateral strike-slip shear zone, the Anatolian Diagonal. The faults bounding and internally deforming the Anatolian Diagonal were closely examined by using high-resolution satellite images, focal mechanism solutions of the earthquakes, and published seismic reflection data in the offshore areas. The Anatolian Diagonal is a NE-SW trending left-lateral shear zone having a 170 km width between the Central Anatolian and the East Anatolian fault zones and an 850 km length between Erzincan and the Cyprus Arc. It has at least four intersection points with the right-lateral North Anatolian Fault Zone and the Southeast Anatolian-Zagros Fault Zone. As the offshore continuation of the Ecemiş-Deliler Fault of the Anatolian Diagonal, the Biruni Fault reaches the Cyprus Arc and Piri Reis (Mediterranean) Ridge Front west of Cyprus. This structure creates a restraining stepover with the left-lateral Antalya-Kekova Fault Zone and causes NW-SE trending thrusts of the Florence Rise and Antalya Thrust in the Antalya Basin. There is another restraining stepover between the Antalya-Kekova Fault Zone and the Pliny-Strabo Fault Zone, where the thrust-controlled northern margin of Rhodes basin developed. In this neotectonic framework, there is no need for the existence of the highly-debated left-lateral Fethiye-Burdur Fault Zone as an onshore continuation of the Pliny and Strabo faults. In fact, the westerly motion of the Anatolian plate is accommodated by the left-lateral Anatolian Diagonal Shear Zone, Antalya-Kekova Fault Zone and Pliny-Strabo Fault Zone together with the right-lateral North Anatolian Fault Zone.

Giant slope scars and mass transport deposits across the Rhodes Basin, eastern Mediterranean: Depositional and tectonic processes

High-resolution multichannel seismic reflection profiles and multibeam mosaic maps of the seafloor are used to document the presence of two prominent regions representing major sediment failure(s) and the subsequent gravity-driven mass transport across the southwestern continental margin of Anatolia. These regions are characterized by very sugged morphology (referred to as Scars 1 and 2), where the upper slope regions include several concave, interconnected steep seafloor escarpments marked by semi-circular indentations that link with one another by cusp-like features creating a sharp and very narrow curvilinear zone. The slope face across the rugged region there are numerous sharply irregular pinnacles/protrusions on the seafloor, consisting of exposed older bedrock successions. Scars 1 and 2 occupy seafloor areas of 1947 km2 and 1350 km2, solid volumes of 214–257 km3 and 92–111 km3, and masses of 467–681 Gt and 245–294 Gt, respectively, with a total solid volume of 307–368 km3 and a mass of 812–975 Gt. Mass transport deposits are identified at various stratigraphic levels across the Rhodes Basin characterized by chaotic seismic reflector configurations with zones of contorted and convoluted reflector geometries. The base of this facies is characterized by erosional down-cutting. The thickest and the regionally most extensive such deposits are found at the base of Unit 1, immediately above the upper bounding surface of the Messinian evaporites (the Top Erosional Surface or the former M-reflector). The lower mass transport deposit (L–MTD) is calculated to have a volume 205–171 km3, or a solid mass of 543–452 Gt, assuming that porosities of 40–50% and average grain density of 2.67 t m−3. Comparisons between the total mass of the L–MTD and the estimated masses of sediments mobilized across Scars 1 and 2 (812–975 Gt) indicate that there is ~360–432 Gt deficit in the calculated mass of the L–MTD. The missing sediments represent 17.5–21.0% of the total mass contained within Unit 1 across the present-day Rhodes Basin. This mismatch is remarkably large: it may arise from the uncertainties involved in the estimations of the masses of sediments contained in Scars 1 and 2; however, it is also possible that some of the gravity driven mass transports transitioned into turbidity currents, thus travelled great distances across the Rhodes Basin, and that some of these turbidity currents crossed the basin longitudinally, and exited it at its southwestern deeper regions (i.e., the present-day Strabo Trench). This is particularly plausible because the physiography of the Rhodes Basin was dramatically different during the early Pliocene and the southern and southwestern portions of the basin provided a possible exit route.

Dramatic Pliocene–Quaternary subsidence of the southern Rhodes Basin and concomitant north-tilting and uplift of the Anaximander Mountains, the junction of Hellenic and Cyprus arcs, eastern Mediterranean Sea

The Anaximander Mountains and the Rhodes Basin at the junction of Cyprus and Hellenic arcs are one of the tectonically most complex regions in the eastern Mediterranean. Harmonically-tilted Messinian and the uppermost Messinian–Pliocene successions across the northern and eastern margins of the Rhodes Basin showed that these regions experienced dramatic subsidence exceeding ~1500–2500 ms (~1125–1875 m @ 1500 m s−1) during the upper Pliocene–Quaternary. Tilted upper Pliocene–Quaternary growth strata wedges showing apparent north-directed downlap along the northern foothills of the Anaximander Mountain suggested that this region experienced ~1000–2500 ms (~750–1125 m) concomitant uplift. The absence of faults showing extensional stratigraphic separations and the relative subsidence rates calculated using amount of tilting collectively suggest that the Rhodes Basin experienced sagging of its deeper basinal regions, which is attributable to the loading effect of the building of the Tauride Mountains modified by the vertical axis rotations of the Beydağları Block and the Island of Rhodes, and the horizontal axis rotation of the Anaximander Mountain.Messinian and uppermost Messinian–Pliocene were tectonically relatively quiet as shown by the harmonically structured and isopachous successions across the Rhodes Basin and Anaximander Mountain. This interval coincides with the paleomagnetically-determined 9° counterclockwise vertical axis rotation of the Island of Rhodes. The dramatic subsidence observed within the Rhodes Basin and the concommitant uplift of the Anaximander Mountain and its western extension occurred broadly coincident with southeast tilting of the Island of Rhodes and its associated 500–600 m subsidence between 2.5 and 1.8 Ma, the northwest tilting between 1.5 and 1.1 Ma, and the associated re-emergence of the southeastern coast. The large counterclockwise rotation of the Island of Rhodes since 0.8 Ma corresponds with the enormous subsidence observed across the northeastern sector of the Rhodes Basin, which brought the shelf-edge deltas from the near-sea level to their present-day depth of 1200–1500 m.

The benthic Copepoda (Crustacea) of Anaximenes Seamount (eastern Mediterranean Sea)—Community structure and species distribution

During research cruise M71/1 of German FV METEOR in winter 2006, meiofauna sampling was undertaken on the eastern Mediterranean Anaximenes Seamount at six sites (the summit, northern slope, north-western slope, north-western base, north-eastern slope and eastern base). Analysis of the benthic Copepoda (i.e. Harpacticoida and Canuelloida) revealed a highly diverse fauna. This is in contrast to what is generally considered an impoverished bathyal and abyssal fauna in the surrounding eastern Mediterranean Sea: It is regarded as one of the most oligotrophic regions of the world’s oceans. This is attested to by comparison of the seamount fauna with that of a remote deep-sea (“Far-field”) site in the Rhodes Basin, which presented a clearly impoverished fauna with respect to abundance, higher-taxon diversity and species diversity. Comparison of sites across the seamount found no overall “seamount community” of benthic Copepoda. Instead, three different assemblages could be detected, with abundance and species diversity comparable to north-eastern Atlantic seamounts and islands. Regarding species composition, however, only four of the recorded species are shared with other Mediterranean and Atlantic elevations. The benthic copepod fauna at Anaximenes Seamount is composed mostly by “typical” deep-sea and eurybathic species, whilst “typical” shallow-water species were absent. Thus, it is concluded that Anaximenes Seamount does not play a role in the dispersal of shallow-water benthic Copepoda. Nonetheless, it appears important for the establishment of abundant and diverse deep-sea communities. Moreover, it constitutes no barrier for the dispersal of deep-sea benthic Copepoda in the Mediterranean.

Seismotectonic content by the source parameters of the 10 June 2012 Ölüdeniz-Fethiye (Dodecanese Islands) Mw 6.1 earthquake and aftershocks (southwestern Turkey)

A detailed source and rupture process analyzes of the 10 June 2012 Oludeniz-Fethiye (Dodecanese Islands; Mw 6.1) earthquake has been carried out using inversion of both complex body waves and strong ground motion records. The rupture starting from the hypocenter propagated gradually to the southwest. The main rupture is modeled by a main asperity located 2–3 km beneath the hypocenter and two small asperities. The size of the effective source area is about 24 × 12 km, the rupture duration was approximately 12 s and the total seismic moment was estimated to be 1.955 × 1018 Nm. Continuation of compression from the Hellenic Arc to the southeast part of Fethiye Gulf in the north developed many active faults with complex geometries in the region. According to the stress field obtained from the focal mechanism solutions of the 10 June 2012 Fethiye (Dodecanese Islands; Mw 6.1) earthquake and M ≥ 3.5 earthquakes which occurred in Fethiye Gulf, the region between Fethiye Gulf and Rhodes Basin was deformed by the NW–SE oriented extension. (T-σ3) principal stress axis is dominant in the region. Additionally, NNW–SSE compression (P-σ1) in further southwest of Fethiye Gulf contributed to forming normal and strike-slip faults. Continuation of the NE–SW trending thrust faults located from the west limb of the Hellenic Arc to the southeast of Fethiye Gulf caused deformation in the region due to the seismotectonic model of the region. Both, normal faulting related to the “pure extension” occurred after the compression, and strike-slip faulting associated with the “transtension”, have been expressed by the spatial positions of the principal stress axes in the study area.

The Fethiye–Burdur Fault Zone: A component of upper plate extension of the subduction transform edge propagator fault linking Hellenic and Cyprus Arcs, Eastern Mediterranean

The Hellenic and Cyprus Arcs, that mark the convergent boundary of the African and Aegean–Anatolian plates, are offset along a subduction transform edge propagator (‘STEP’) fault running NE–SW along the Pliny and Strabo Trenches. The continuation of the fault to the northeast through the Rhodes Basin and into SW Anatolia is assessed. Seismic reflection profiles show that the structural architecture of the northern sector of the Rhodes Basin includes a large crustal-scale fold–thrust belt which is overprinted by numerous faults with small extensional stratigraphic separations. A protracted episode of convergence in the Miocene resulted in the development of a prominent NE–SW-striking and NW-verging fold–thrust belt in the Rhodes Basin. The absence of evaporites in the Rhodes Basin and several seaward prograded vertically stacked Quaternary delta successions resting at 2500–3500m water depth collectively suggest that the Rhodes Basin must have remained above the depositional base of marine evaporite environment during the Messinian and that the region must have subsided very rapidly during the Pliocene-Quaternary. During the Pliocene-Quaternary, a NE–SW-trending belt developed across the Rhodes Basin: while the structural framework of this belt was characterised by reactivated thrusts in the central portion of the basin, a prominent zone of NE–SW-striking and NW- and SE-dipping faults with extensional separations developed in the northern portion of the basin. Two seismic profiles running parallel to the present-day coastline provide the much needed linkage between the Fethiye–Burdur Fault Zone onland and the reactivated thrusts in central Rhodes Basin, and show that the Pliocene-Quaternary zone of high-angle faults with extensional separations clearly link with the similarly trending and dipping strike–slip faults onland in the Eşen Valley, thus providing the continuity between the Pliny–Strabo Trenches in the southwest and the Fethiye–Burdur Fault Zone in the northeast. Mapping of many faults in parts of the Fethiye–Burdur Fault Zone shows evidence for sinistral strike–slip but total displacement across the fault zone is at maximum a few tens of kilometres. The STEP fault thus appears to have diminishing displacement associated with it as it propagates upwards into the upper plate from its originating tear in the subducting plate.

Investigation of Fethiye-Marmaris Bay (SW Anatolia): seismic and morphologic evidences from the missing link between the Pliny Trench and the Fethiye-Burdur Fault Zone

New (2009) multi-beam bathymetric and previously published seismic reflection data from the NE-SW-oriented Fethiye Bay and the neighboring N-S-oriented Marmaris Bay off SW Anatolia were evaluated in order to interpret the seafloor morphology in terms of the currently still active regional tectonic setting. This area lies between the Pliny Trench, which constitutes the eastern sector of the subduction zone between the African and Eurasian plates in the Eastern Mediterranean, and the Fethiye-Burdur Fault Zone of the Anatolian Plate. The bathymetric data document the very narrow shelf of the Anatolian coast, a submarine plain between the island of Rhodes and Marmaris Bay, and a large canyon connecting the abyssal floor of the Rhodes Basin with Fethiye Bay. The latter are here referred to as the Marmaris Plain and Fethiye Canyon, respectively. Several active and inactive faults have been identified. Inactive faults (faults f1) delineate a buried basin beneath the Marmaris Plain, here referred to as the Marmaris Basin. Other faults that affect all stratigraphic units are interpreted as being active. Of these, the NE-SW-oriented Marmaris Fault Zone located on the Marmaris Plain is interpreted as a transtensional fault zone in the seismic and bathymetric data. The transtensional character of this fault zone and associated normal faults (faults f3) on the Marmaris Plain correlates well with the Fethiye-Burdur Fault Zone on land. Another important fault zone (f4) occurs along the Fethiye Canyon, forming the northeastern extension of the Pliny Trench. The transpressional character of faults f4 inferred from the seismic data is well correlated with the compressional structures along the Pliny Trench in the Rhodes Basin and its vicinity. These observations suggest that the Marmaris Fault Zone and faults f3 have evolved independently of faults f4. The evidence for this missing link between the Pliny Trench and the Fethiye-Burdur Fault Zone implies possible kinematic problems in this tectonic zone that deserve further detailed studies. Notably, several active channels and submarine landslides interpreted as having been triggered by ongoing faulting attest to substantial present-day sediment transport from the coast into the Rhodes Basin.

Zooplankton at a seamount in the eastern Mediterranean: distribution and trophic interactions

The study focuses on the question, how a seamount in the oligotrophic eastern Mediterranean affects the zooplankton community, as compared to the open water. Zooplankton samples were taken with 333 µm nets at two sites, the Rhodes Basin and the Anaximenes Mountain, in December 2006. The samples were sieved into size fractions, and the composition, biomass, abundance and stable isotope signatures were analysed. In general, biomass and abundance of zooplankton were low, reflecting the oligotrophic character of the eastern Mediterranean, but zooplankton standing stocks were higher at the Rhodes Basin than at the Anaximenes Mountain. Stable isotope signatures showed, at a generally low level, enrichment in zooplankton taxa along the food chain within the different pelagic zones and from the surface to the deep-sea, but no significant differences between Rhodes Basin and the seamount were evident in the food web structure. The zooplankton community in the Anaximenes Mountain region in the northern Levantine Basin seems not to be influenced by a local seamount effect, despite the difference in standing stocks between the seamount and the Rhodes Basin. This seems to be driven by larger-scale upwelling and downwelling structures of cyclones and anticyclones, dominating the circulation in the area.

Structural architecture of the Rhodes Basin: A deep depocentre that evolved since the Pliocene at the junction of Hellenic and Cyprus Arcs, eastern Mediterranean

Interpretation of ~ 1500 km of multi-channel seismic reflection profiles shows that the Rhodes Basin evolved in two distinct tectonic stages. A protracted Miocene convergence (episode P1) resulted in the development of a mainly SSE-verging fold–thrust belt. This period corresponds with the emplacement of the Lycian Nappes to the northeast and fold/thrust complexes on the Island of Rhodes to the west. This phase of deformation ceased in the late Miocene. The absence of evaporites in the Rhodes Basin suggests that this region must have remained above the depositional base of marine evaporite environment during the Messinian. The morphology of the M-reflector, and the architecture of the lowermost Pliocene growth strata in the central portion of the Rhodes Basin demonstrate the existence of rugged paleo-relief over the pre-existing Miocene fold–thrust belt in early Pliocene. The middle Pliocene–Quaternary phase of deformation is characterised by NE–SW sinistral transpression (P2), and rapid regional subsidence. The P2 deformation occurred in response to an actively curving Hellenic Arc and the increasing obliquity of its eastern limb, the Pliny–Strabo Trenches (or fault zones) to the convergence vector of the African Plate. During this time, the P1 structures became re-activated as transpressional faults, further facilitating the rapid subsidence. We envisage the evolution of the Rhodes Basin as the result of subsidence associated with loading of the large imbricate thrust panels that carry the western Tauride Mountains in the north. At present, the Pliny–Strabo fault zones are delineated as a NE–SW trending 30–50 km-wide zone that continue into the western segment of the Rhodes Basin. This fault zone is further correlated with the similar trending ~ 50 km-wide Burdur–Fethiye Fault zone in southwestern Turkey.

Timing of Late Pliocene to Middle Pleistocene tectonic events in Rhodes (Greece) inferred from magneto-biostratigraphy and 40Ar/ 39Ar dating of a volcaniclastic layer

We discovered a volcaniclastic layer in the Plio-Pleistocene coastal sequences on the island of Rhodes (Aegean fore-arc, Greece). Here, we present an integrated isotopic, magnetostratigraphic, and biostratigraphic (planktonic foraminifers) study for the Haraki section, where this layer is found intercalated in several meters of sedimentary rocks corresponding to the Lindos Bay clay Member of the Rhodes Formation. 40Ar/ 39Ar dating of the volcaniclastic layer provides an age of 1.89 ± 0.09 Ma, which is consistent with our planktonic foraminiferal data. Magnetostratigraphic results show that the entire Haraki section is of normal polarity and according to the isotopic results this corresponds to the Olduvai subchron (1.95–1.77 Ma). The new age determination provides severe constraints for deciphering the sedimentary and tectonic evolution of Rhodes since the Late Pliocene, which can be summarized in the following: (1) 500 to 600 m drowning during the latest Pliocene that could be related to the westward motion of the Anatolian Plate; (2) at least 520 m of uplift at around 1.4–1.3 Ma related to activity of the sinistral strike-slip of the Pliny Trench, the deep Rhodes basin being separated from the island of Rhodes; (3) a counterclockwise rotation of Rhodes, younger than 1.2–1.1 Ma, and possibly synchronous with the young clockwise rotation of the western Aegean arc.

Eastern Mediterranean basin systems

Abstract The basins in the Eastern Mediterranean can be divided into those that were formed mainly in post-Miocene time and those that were formed during the rifting episodes that led to the formation of the Neotethys. The younger basins can be further divided into those that were formed mainly in post-Miocene time and those that were formed in post-Pliocene time. The separation is not only one of convenience but also corresponds to major adjustments in the plate tectonic situation in the Eastern Mediterranean. The late Miocene deposition of thick evaporites throughout the Mediterranean region, or, where evaporites are missing, the creation of an important erosional unconformity during the extreme lowstand of the Mediterranean, makes the Miocene-Pliocene boundary relatively easy to identify, especially on seismic reflection records. At about the same time, following the collision of the Arabian plate with Eurasia, the Anatolian and Aegean microplates came into existence between the convergent African and Eurasian plates to accommodate tectonic escape between them. The general configuration of the Eastern Mediterranean basins reflects the tectonic and structural gradients between the collisional domain of southeastern Turkey and Iran, and the continuing but increasingly limited subduction along the Calabrian and Hellenic arcs, with the Cyprus and Levantine zones between them. Several distinct zones can be identified in the Eastern Mediterranean. The Dead Sea Fault system marks the edge between the collisional and pre-collisional zones to the east and west, respectively. The meridian through the Anaximander Mountains (30©E) forms a rough boundary between the zone of incipient collision to the east and the zone of continuing but late-stage subduction to the west. The Malta Escarpment forms the Eastern boundary of the Eastern Mediterranean basins. The series of basins along the northern margin of the Eastern Mediterranean and the Aegean Sea share this progressive evolution, with those containing Messinian evaporites to the east and those without to the west. The Sicily Channel with its associated basins is an extensional zone between the Eastern and Western Mediterranean. The basins discussed in this paper are divided into two groups, the larger and older basins and the smaller and younger basins. In the first group are the Ionian Basin and the Levantine Basin, and in the second group the Cilicia Basin, Antalya Basin, Finike Basin, Rhodes Basin, Aegean basins, Sicily Channel basins, Latakia Basin and Larnaca Basin. The Eastern Mediterranean represents the last stage in the evolution of an ocean basin. Given the current motion between Africa and Eurasia, the Eastern Mediterranean will cease to exist in about 6-8 Ma from now. As a result, the larger and older basins are shrinking, whereas the younger and smaller basins are growing. Eventually the smaller basins will also disappear.

The Anaximander Mountains: a clue to the tectonics of southwest Anatolia

AbstractThe offshore Anaximander Mountains are an important link between the Hellenic and Cyprus arcs. They were formed by southeastward rifting from Turkey in post‐Miocene time. Gravity data have shown that the eastern part of the Anaximander Mountains is different from the western part; multibeam mapping seems to confirm that the eastern Anaximander Mountains have affinity with the Florence Rise structure (western Cyprus Arc). Faulting along and across the latter feature is characterized in the seismic data by anastomosing faults and pop‐up flower structures. It is likely that progressive adjustment to incipient collision developed into a broad zone of NW–SE transpressive wrenching extending towards south Turkey. In contrast, the western mountains are more directly related to the opening of the Rhodes Basin and the Finike Basin, as transtension may have dominated in southwest Turkey since the Pliocene. The connection with onshore Turkey is still unclear, but could be related to the Fethiye–Burdur Fault Zone that defines the western boundary of the complex Isparta Angle. The Anaximander Mountains and the Isparta Angle form together a tectonic accommodation zone between the active deformation in southwestern Turkey and the Aegean region and the tectonically quieter Cyprus region. Copyright © 2003 John Wiley & Sons, Ltd.

The Rhodes Basin, a post-Miocene tectonic trough

Abstract New light is shed on the enigmatic Rhodes deep marine basin by a set of underway geophysical data across it, including swath bathymetry, seismic reflection profiles, gravity and magnetic data. This deep trough (as much as 4485 m) to the east of the Island of Rhodes and close to southwestern Turkey, contains no Messinian evaporites and only a thin Pliocene–Quaternary sedimentary section (

Simulations of biological production in the Rhodes and Ionian basins of the eastern Mediterranean

The biological production characteristics of the Rhodes and western Ionian basins of the eastern Mediterranean are studied by a one-dimensional, coupled physical–biological model. The biological model involves single aggregated compartments of phytoplankton, zooplankton, detritus as well as ammonium and nitrate forms of the inorganic nitrogen. It interacts with the physical model through the vertical eddy diffusivity which is calculated using the Mellor–Yamada level 2.5 turbulence parameterization. The model simulations demonstrate the importance of the contrasting physical oceanographic characteristics of these two basins on affecting their yearly planktonic structures. The annual primary production in the Rhodes basin is estimated as ∼97 g C m 2 yr −1 which is comparable with the northwestern Mediterranean. The western Ionian basin, on the contrary, possesses only 10% of the Rhodes' productivity and therefore represent a most oligotrophic site in the eastern Mediterranean. The Rhodes basin reveals a strong bloom in early spring, typically in March, a weaker bloom in early winter, typically in January, and a subsurface production below the seasonal thermocline during summer. This structure is slightly modified in the western Ionian basin, and the early winter and early spring blooms are merged to cover the entire winter. These results are supported favorably by the available observations both in their magnitudes and timing.

The Hellenic margin from eastern Crete to Rhodes: Preliminary results

Complementary data on previously surveyed areas have been obtained and more than 3000 km of continuous seismic profiles along the eastern Hellenic continental margin, between eastern Crete and Rhodes, have been made. Among the important preliminary observations, we note: the relatively great thickness, due to probable coarse rapid fill, of the margin sedimentary cover, which is also intensively affected by extensional faulting. The presence of a well-defined sedimentary basin (lying between the Strabo- and Pliny Trench), where evaporitic strata exist but where the acoustic facies also suggest coarse fill, is probably derived from surrounding topographical highs exposed to erosion during the Messinian. Finally we observe a progressive and perplexing change of the Strabo Trench structural pattern from west to east, which indicates a more complex tectonic regime than we expected. We speculate that at the southern margin of the Rhodes Basin, northward thrusting may now be occurring.

Evidence for northward thrusting south-west of the Rhodes Basin

Models of convergence between the major African and European plates involve a stretching Aegean plate, whose present motion relative to Africa is south-west1–3. This motion has resulted in subduction of eastern Mediterranean sea floor as shown by seismicity, volcanism and morphology. The southern boundary of the Aegean plate is formed by the Hellenic Trench. Intensive study, culminating in the use of submersibles and multibeam echo-sounding as part of the Hellenic Arc and Trench Program4, has outlined the complexity of this boundary. Detailed reflection profiling which we carried out in autumn 1980 of the eastern portion of the Hellenic Trench system shows arcward verging thrusting south-west of the Rhodes Basin. We conclude that collision of the African continental margin with the Hellenic Arc is now in progress, causing overriding by the Mediterranean Ridge along the southeastern branch of the Hellenic Trench system.