Cenk Yaltırak

Tectonic evolution of the Marmara Sea and its surroundings

Abstract The basins in the Marmara Sea are the products of a superimposed evolutionary history defined by two different-aged fault systems: the early Miocene–early Pliocene Thrace–Eskisehir Fault Zone and its branches, and the late Pliocene–Recent North Anatolian Fault and its branches. The Thrace–Eskisehir fault and its westward branching secondary fault systems define the early neotectonic signature in the region. The late neotectonic period started at the end of the early Pliocene when the North Anatolian Fault divided the Thrace–Eskisehir fault into four parts. During the late neotectonic period, the North Anatolian Fault extended westward as a number of splays by joining with the Ganos, Bandirma–Behramkale and Manyas–Edremit Fault Zones. The branches of the North Anatolian Fault Zone (NAFZ) caused the evolution of a number of basins, which differ in character depending on the trend and past characteristics of the older branches that became connected. Since the northern branch of the North Anatolian Fault is connected to the N80°E-trending Ganos Fault Zone (GFZ) in the west, a single buried fault has developed in the Marmara Sea, causing the well-known troughs and ridges, superimposed onto the negative flower structure formed by the GFZ in the early neotectonic period. The middle strand, which extends from Iznik Lake to Bandirma, is oriented east–west up to the N60°E-trending Bandirma–Behramkale Fault Zone, then turns southward in the vicinity of Bandirma, forming a region dominated by compressional tectonics. This bending caused N30°E-trending tension in addition to the strike-slip motion between the eastern part of Gemlik Bay and Bandirma Bay. The southern branch of the NAFZ, on the other hand, produced three pull-apart basins with different characteristics along the Yenisehir, Bursa and Manyas segments. The southern branch of the NAFZ connected to the Manyas–Edremit Fault Zone, which is oriented N45°E to the south of Manyas, and the associated bending and rotation caused a N15°E-trending extension in addition to the strike-slip regime between Manyas and Uluabat. The branches of North Anatolian Fault cut through the Thrace–Eskisehir fault at three places: the East Marmara Sea region, in Gemlik Bay, and to the east of Bursa, giving lateral offsets of 58–59, 7–8 and 10–11 km, respectively. The cumulative motion is 75–78 km, corresponding to the total lateral offset of the North Anatolian Fault in the region. The correlation of these offsets with Global Positioning System slip vectors and with stratigraphic results implies that the North Anatolian Fault reached into the Marmara Sea region about 3.5 million yr ago. Tectonic processes forming the Marmara Sea and its environs were initiated by the Thrace–Eskisehir fault and its splays have been most recently controlled by the North Anatolian Fault and its splays during the last 3.5 million yr.

Palaeogeographical evolution of the Thrace Neogene Basin and the Tethys-Paratethys relations at northwestern Turkey (Thrace)

Abstract The Thrace Neogene Basin situated in northwestern Turkey was initiated by strike-slip faulting that was active from the Early Miocene until the end of the Pliocene. During the Early Miocene, it began to form under the control of the Thrace–Eskisehir Fault Zone, initiated by continental collision in northwestern Anatolia (Late Oligocene–Early Miocene). During the late Early Miocene, the basin was a site of mainly fluviatile and limnic sedimentation to the west and marine sedimentation via the Paratethyan transgression in the north. With the onset of the Middle Miocene, the Thrace Block started to rotate in a counterclockwise sense and escaped westward with respect to the Strandja–Istanbul block owing to rejuvenation of fossil fault systems within it. In this period, warm marine conditions were also established around the Gulf of Saros through a Mediterranean originated transgression. During the Middle–Late Miocene fluviatile and limnic conditions were created over the western Thrace by the westerly propagation of the Thrace–Eskisehir Fault Zone. One of the principal results of the Early–Middle Miocene tectonics is the tilting of the Strandja–Istanbul Block to the south, severing the Tethys and the Paratethys. During the latest Miocene–Early Pliocene period, the Thrace–Eskisehir Fault Zone was deactivated because of the evolution of the North Anatolian Fault Zone to the south. The resurrected Ganos Fault Zone situated on the dissected fossil suture zone in the Sea of Marmara also joined the North Anatolian Fault Zone, uplifting the Gelibolu Peninsula and, thus, severing the connection that existed between the Sea of Marmara and the Paratethys. The Sea of Marmara eventually became an endemic basin by the activity of the North Anatolian Fault Zone.

Tectonic elements controlling the evolution of the Gulf of Saros (northeastern Aegean Sea, Turkey)

Abstract Tectonic elements controlling the evolution of the Gulf of Saros have been studied based upon the high-resolution shallow seismic data integrated with the geological field observations. Evolution of the Gulf of Saros started in the Middle to Late Miocene due to the NW–SE compression caused by the counterclockwise movement of the Thrace and Biga peninsulas along the Thrace Fault Zone. Hence, the North Anatolian Fault Zone is not an active structural element responsible for the starting of the evolution of the Gulf of Saros. The compression caused by the rotational movement was compensated by tectonic escape along the pre-existing Ganos Fault System. Two most significant controllers of this deformation are the sinistral Ganos Fault and the dextral northern Saros Fault Zone both extending along the Gulf of Saros. The most important evidences of this movement are the left- and right-oriented shear deformations, which are correlated with structural elements, observed on the land and on the high-resolution shallow seismic records at the sea. Another important line of evidence supporting the evolution of this deformation is that the transgression started in the early-Late Miocene and turned, as a result of regional uplift, into a regression on the Gelibolu Peninsula during the Turolian and in the north of the Saros Trough during the Early Pliocene. The deformation on the Gelibolu Peninsula continued effectively until the Pleistocene. Taking into account the fact that this deformation affected the Late Pleistocene units of the Marmara Formation, the graben formation of the Gulf of Saros is interpreted as a Recent event. However, at least a small amount of compression on the Gelibolu Peninsula is observed. It is also evident that compression ceased at the northern shelf area of the Gulf of Saros.

Origin of the Sea of Marmara as Deduced from Neogene to Quaternary Paleogeographic Evolution of its Frame

The Sea of Marmara Basin (SMB) is connected to the fully marine Mediterranean by the Dardanelles strait and to the brackish Black Sea by the Thracian Bosporus. This linkage to two different marine realms with contrasting water chemistry has been a prime control on the sedimentary history of the SMB, which in turn was controlled by its tectonics. Isolation from any of these realms resulted in drastic changes in its paleoceanographic conditions and made it a part either of the global ocean system or of a brackish-marine environment, depending on the realm from which the connection was severed. The SMB represents the inundated part of the northwestern Anatolian graben system that resulted from the interaction between the North Anatolian fault (NAF) zone and the present N-S extensional tectonic regime of the Aegean. The geologic history of this basin began during the late Serravallian when the NAF was initiated. The first inundation of the basin coincided in both time and space with this initiation. The invad...

Late Pleistocene uplift history along the southwestern Marmara Sea determined from raised coastal deposits and global sea-level variations

Pleistocene raised coastal deposits characterized by locally abundant shells, aragonite-cemented beachrock and associated nearshore deposits border the western Marmara Sea at elevations of 0–50 m. Field observations confirm that these deposits formed during a series of transgressive and regressive events. U/Th dates in 16 in situ shells from four localities show that the peak of the transgressions occurred during the highstands of oxygen isotopic stages 7 and 5, between ∼53 and ∼210 ka. The elevations of these dated deposits can be used to quantify their post-depositional uplift and indicate that the entire western Marmara shelf, including the Strait of Canakkale (Dardanelles) has been rising at an average rate of ∼0.40 mm yr−1 since ∼225 ka. The primary cause of uplift is the local compression associated with a restraining bend in the western segment of the North Anatolian Fault. Paleogeographic maps constructed using the average rate of tectonic uplift and detailed topographic and bathymetric maps reveal that prior to glacial oxygen isotopic stage 8 the Marmara Sea was never isolated from the Aegean Sea, even when global sea level was low, because the floor of the Strait of Canakkale was too deep early in its uplift history. The dominance of Mytilus edulis in raised coastal terraces dating from the lowstand of glacial oxygen isotopic stage 8 suggests that the degree of communication between the Aegean Sea and Marmara Sea was comparable to that of the present. During the peak of glacial oxygen isotopic stage 6, the floor of the strait was subaerially exposed, isolating the Marmara Sea for the first time in the Pleistocene from the higher salinity Mediterranean water inflow and possibly causing it to become a blackish-water lake. During interglacial isotopic stages 9, 7 and 5, the Strait of Canakkale was very wide and deep (∼100–125 m), and there were two subsidiary channels (Bolayir and Eceabat channels), providing additional links between the Aegean Sea the Marmara Sea, further promoting significant water exchange between these basins. The dominance of Ostrea edulis in the raised terraces dating from isotopic stages 5 and 7 confirms an enhanced penetration of the Mediterranean water mass into the Marmara Sea. The history of communication between the Black Sea, fed by central and northern European drainage systems, and the low-latitude Mediterranean Sea is of fundamental importance in understanding the genesis of organic-rich sapropel deposits throughout the region. The results presented in this paper caution against the simple assumption that sea-level change alone controlled the degree of connection across this oceanographic gateway. Instead, the physiography and paleoceanography of the region were controlled both by variations in global sea level and the rate of uplift in an area of active transpression.

Kinematics and evolution of the northern branch of the North Anatolian Fault (Ganos Fault) between the Sea of Marmara and the Gulf of Saros

Abstract The WSW–ENE-trending Ganos Fault is a dextral strike-slip fault running parallel to and southwest of the West Marmara Trough and south of the Saros Trough. Dextral structures started evolving in the early Miocene, and at this time the Ganos fault system developed from a part of the Thrace–Eskisehir fault system. Beginning in the late Pliocene (∼3.5 Ma), the North Anatolian transform fault propagated into the Marmara region and captured the Ganos Fault. Subsequently, this fault has accommodated the westward movement of the Anatolian Block. Because of the curvature of the microplate boundary in this area, the Ganos fault system has tended to rotate counterclockwise. Farther west in the Gulf of Saros, the strike-slip motion was accommodated by a new fault on the northern margin of the gulf, rather than along the northern coast of the Gelibolu Peninsula as previously thought. This interpretation differs from previous assessments of the position of the northern strand of the North Anatolian fault (Marmara segment) in the Marmara Sea and in the Gulf of Saros. The role of the Ganos Fault proposed in this paper is considerably different from that proposed by earlier studies. While the revised orientation of the North Anatolian fault on land is about 7° different than specified by previous authors, at sea it is different by ∼32° counterclockwise and ∼23° clockwise in the West Marmara and Saros submarine depressions, respectively. The revised position of the Ganos Fault in the Marmara Sea, derived from shallow and conventional seismic reflection data, calls into question the validity of evolutionary models previously used in kinematic and stress-failure analyses. In particular, it is not possible to regard the Marmara Sea as a pull-apart basin and the Gulf of Saros as a transtensional half-graben. Furthermore, palinspastic maps taking into account the revised position of the Ganos Fault and GPS slip vectors support the idea that a dextral master fault is present to the north of the Saros Trough with a sinistral oblique fault dominated by normal offset (Gelibolu Fault) to its south. The Gelibolu Fault is reactivated in a limited region.

Evolution of the middle strand of North Anatolian Fault and shallow seismic investigation of the southeastern Marmara Sea (Gemlik Bay)

Abstract The Gemlik Bay is developed as a pull-apart basin during the late Pliocene-early Pleistocene mainly controlled by west-trending dextral strike-slip faults along the middle strand of the North Anatolian Fault zone, with the NW-trending Thrace-Eskisehir Fault playing secondary role. The North Anatolian Fault reached the eastern Marmara Sea ∼3.5 Ma ago, where its middle strand intersected the Thrace-Eskisehir Fault. GPS slip vectors measured on the Armutlu and Mudanya blocks show a displacement of 7–8 km during the last 3.5 Ma. The middle strand of the North Anatolian Fault zone has lower tectonic activity than the northern strand. Because uplift of the southeast Marmara Sea region has been continuous since the late Pliocene, the presence of fluviatile, lacustrine and deltaic environments in the Gemlik pull-apart basin over the same period supports a lower lever of tectonic activity. The transgressive Marmara Formation was deposited on top of these fluvio-lacustrine deposits following the Mediterranean inundation at ∼600 ka via the Strait of Canakkale. The Gemlik basin was affected both by two major sea-level falls at 160–132 and 24–11 ka, and minor short-lived sea-level variations, as a result of becoming a lacustrine setting five times since ∼600 ka. During these lowstands, stacked delta successions were deposited around the lake and on the transgressed shelves of the Marmara Sea.

The effects of the North Anatolian Fault Zone on the latest connection between Black Sea and Sea of Marmara

Abstract The development of the Strait of Istanbul is also one of the principal results of the tectonics which led to the evolution of the North Anatolian Fault Zone (NAFZ) in the Marmara Region 3.7 Ma ago. High resolution seismic profiles from the Marmara entrance of the Strait of Istanbul show a folding which occurred after the deposition of the parallel reflected Tyrrhenian sediments. Over the Tyrrhenian strata, a fondoform zone of a deltaic sequence and marine sediments of the latest sea level rising are present. These sediments also display syn-depositional folding. This situation implies that a local compressional stress field was created over the area probably since the Wurm Glacial age. This recent variation of the tectonic regime in the northern shelf of the Sea of Marmara may indicate a significant change in the development of the NAFZ through the Sea of Marmara. This variation of evolution of the NAFZ affected the latest development of the Strait of Istanbul via clockwise rotation of the Istanbul and Kocaeli peninsulas by right-lateral shearing between two zone bounding faults. This rotation has led to the development of NNE–SSW left-lateral faults in the Strait of Istanbul and local compressional and tensional areas explaining the compressional structures seen in the southern entrance of the Strait of Istanbul. Therefore, the latest Mediterranean–Black Sea connection was established by means of the sufficient deepening of the Bosphorus channel by a variation in the evolution of NAFZ through the Sea of Marmara.

Şarköy-Mürefte 1912 Earthquake's Tsunami, extension of the associated faulting in the Marmara Sea, Turkey

The historical tsunamis in the Marmara Seawere mainly caused by earthquakes andneeded to be documented. Following 1999Izmit earthquake occurred at the EasternMarmara region, a complete inventory ofactive faults in the Marmara Sea regionbecame much more stressed. To the west, thelatest event is 09.08.1912Şarköy-Mürefte Earthquake. Itoccurred on the active Ganos Fault zone andwas one of the largest earthquakes in theBalkans. The eastern termination of theassociated faulting is in the deep WestMarmara Trough, westernmost of thesuccessive basins forming the Marmara Sea.On the basis of recent multibeam bathymetryand seismic reflection data, estimatedtotal length of the surface rupture isabout 56 km. The historical data reviewedfrom library and archive documents,geological field surveys and offshoregeophysical investigations have shown thatthe 1912 earthquake produced a tsunami. Inaddition a seabed dislocation, the sourceof 1912 tsunami can also be assigned to thesediment slumps appearing in the form ofechelon landslide prisms along the southernslopes of the West Marmara Trough.

Quaternary paleoclimatic-paleoceanographic and tectonic evolution of the Marmara Sea and environs

Strabo (63 BC^21 AD; Book 1.3.4; Jones,1954).TheMarmaraSea(Fig.1)hasalwaysattractedinterestasagreatgatewaylinkingtheBlackSeato the eastern Mediterranean Sea through a net-work of narrow straits with shallow sills: Straitsof Bosphorus (Istanbul) and Dardanelles(C:anakkale).Forthepast2500^3000yr,informa-tion about surface and bottom currents, depthsoundings and sea-level variation were crucialforsafenavigationacrossthesestraitsbysea-far-ingpeopleandexplorers,thusconstitutingama-jorstrategicassetandyieldingenormouseconom-icandpoliticaladvantages.Throughoutantiquity,sailors knew that the bottom waters across theStraits of Dardanelles and Bosphorus £owednorthward, and utilized this knowledge to sailintotheMarmaraSeaandBlackSeabyloweringlargebasketswithweightsintothenorth-£owingMediterranean water to counteract the strongsouth-directed surface out£ow from the BlackSea.Systematic scienti¢c investigations in the Mar-maraSearegionstartedinthelate19thcentury.The¢rstbathymetricsurveyrevealedthepresenceof three deep basins and their intervening ridges(Andrussow, 1901). P|nar (1943) subsequentlyproposedthatasinglefaulttransectedthesethreebasins, extending from the Izmit Bay in the eastto the Gulf of Saros in the west. Pfannensteil(1944) noted the rhombohedric shape of thedeepMarmaraSeabasinsandproposedthattheridgesseparatingthebasinsrepresenthorstblocksbounded by normal faults. Healsosuggested, inadditiontotheStraitofBosphorus,thepresenceofasecondchannel,theSakaryaBosphorus(Fig.1), which connected the Black Sea to the Mar-mara Sea during the Quaternary. In 1948, Ketinpublished his renowned paper revealing the truenatureoftheNorthAnatolianfaultasoneoftheworld’slargest active intra-continental strike^slipfaults (Ketin, 1948). Pavoni (1961) and Kopp etal.(1969)proposedthataseriesofsyntheticand