BATI ANADOLU'DAKİ TERSİYER VE KUVATERNER YAŞLI VOLKANİK KAYAÇLARDA YENİ YAPILAN RADYOMETRİK YAŞ ÖLÇÜMLERİNİN YORUMU

Batı Anadolu'da geniş alanlarda yüzlekler veren ve çeşitli evrelerde meydana gelen Tersiyer ve Kuvaterner yaşlı volkanik kayaçlardan 17 örnek alınarak yaş problemlerine açıklık getirmek için K/Ar ve Rb/Sr yöntemleri ile radyometrik yaş ölçümleri yapılmış ve volkanizmanın bölgesel yorumlanmasına katkı sağlayacak jeokimyasal veriler elde edilmiştir. Ölçülen en eski yaş 18,0 ± 0,2 milyon yıl olarak andezit türde ve kalkalkalen nitelikli Selendi volkanitlerine, en yeni yaş ise 100.000-200.000 yıl ile alkali nitelikli bazaltik Kula volkanitlerine aittir

Application of multivariate statistical approach to identify heavy metal sources in bottom soil of the Seyhan River (Adana), Turkey

WOS: 000276655700026PubMed ID: 19381847In this study, freshly deposited soils were sampled from the Seyhan River (Turkey) from the exit of the Seyhan Dam to the Adana exit. Heavy metal contents were measured with X-ray fluorescence spectrometer. Multivariate statistical approach is used to identify the sources of heavy metals and other elements in soil samples. Considering the size of anomalies, metals are ranked as Co > Pb > Cr > Zn > Al. Based on the hierarchical cluster analysis results, three clusters were observed. P, Mg, Ti, Fe, Ca, Na, K, Al, Si, and Nb form the first cluster, Zn, Sr, Pb, and Cr associated as the second cluster, and Ba and Co form the third cluster. Three factors computed from principal component analysis are explained with a cumulative variance of 95%. The first factor is defined with "high background lithogenic factor" Co, the second factor with "local industrial factor" Pb, Cr, Ba, and Mg, and the third factor with "natural factor" Cr and Pb

MARMARA DENiZi ÇEVRESİNDEKİ TERSİYER VOLKANİZMASININ ÖZELLİKLERİ

Marmara denizi çevresinde, 1/500.000 ölçekli istanbul paftasının kapsadığı alanda Üst Kretase'de başlayıp Üst Miyosen sonlarına kadar aralıklı olarak devam eden volkanizma Üst Kretase, Eosen, Oligosen, Alt-Orta Miyosen ve Üst Miyosen yaşlı olmak üzere farklı 5 evreye ayırtlanmış ve bu geniş alandaki volkanik yüzleklerin tümü yaşlarına göre belirlenmişlerdir. Yapılan ayrıntılı petrografik çalışmaların yanısıra, yaş sorununu aydınlatmak amacıyla farklı alanlardan ve evrelerden alınan 9 örnekte K/Ar yöntemi ile radyometrik yaş ölçümü yapılarak en eski lavın 74, 3 ± 1,0 milyon yıl (Üst Kretase), en yeni lavın ise 8,9 ± 0,2 milyon yıl (Üst Miyosen) yaşta oldukları saptanmıştır,ilk 4 volkanik evreye ilişkin lavlar çoğunlukla kalkalkalen (Eosen yaşlı olanların bir kısmı toleyitik) nitelikte olup, bazalt, bazaltik andezit, trakiandezit, andezit, dasit, riyolit türde; beşinci ve son evreye ilişkin lavlar ise alkalen nitelikli ve bazanit, bazalt ve trakibazalt türdedir, ilk 4 evreye ilişkin volkanizmanın yer yer de tüf ve değişik boyutlu piroklastikleri geniş alanlarda yüzlekler verirler. Üst Kretase yaşlı volkanitier tamamen denizaltında meydana gelmişlerdir. Eosen yaşlı volkanitlerin bir kısmı deniz altında, bir kısmı ise karada meydana gelmiş olup denizel ortamda oluşanlar yer yer çökel kayalarda ardalanmalı olarak gözlenirler. Oligosen, Alt-Orta Miyosen ve Üst Miyosen yaşlı lavlar ise tamamen kıta içinde meydana gelmiş olup yer yer de gölsel ortamda meydana gelen çökel kayalarla birarada bulunurlar. Karadeniz kıyıları boyunca uzanan Üst Kretase yaşlı lavlar bir yitim zonunda türeyen ada yanı volkanitleri grubu içinde; Eosen, Oligosen ve Alt-Orta Miyosen yaşlı lavlar çarpışma ve çarpışma sonrası sıkışma ortamlarında meydana gelmişler ve kabuk ile manto karışımı bir malzemeden türemişlerdir. Üst Miyosen yaşlı alkali bazaltik volkanitlerin ise bölgede tektonik rejimin Orta Miyosen'den sonra değişmesiyle gerilmeli bir ortamda manto yükselmesi sonucu meydana geldikleri düşünülmektedir

Palaeoseismology of the North Anatolian Fault near the Marmara Sea: implications for fault segmentation and seismic hazard

We conducted palaeoseismic studies along the North Anatolian fault both east and west of the Marmara Sea to evaluate its recent surface rupture history in relation to the well-documented historical record of earthquakes in the region, and to assess the hazard of this major fault to the city of Istanbul, one of the largest cities in the Middle East. Across the 1912 rupture of the Ganos strand of the North Anatolian fault west of the Marmara Sea, we excavated 26 trenches to resolve slip and constrain the earthquake history on a channel–fan complex that crosses the fault at a high angle. A distinctive, well-sorted fine sand channel that served as a marker unit was exposed in 21 trenches totaling over 300 m in length. Isopach mapping shows that the sand is channelized north of the fault, and flowed as an overflow fan complex across a broad fault scarp to the south. Realignment of the feeder channel thalweg to the fan apex required about 9±1 m of reconstruction. Study of the rupture history in several exposures demonstrates that this displacement occurred as two large events. Analysis of radiocarbon dates places the age of the sand channel as post ad 1655, so we attribute the two surface ruptures to the large regional earthquakes of 1766 and 1912. If each was similar in size, then about 4–5 m of slip can be attributed to each event, consistent with that reported for 1912 farther east. We also found evidence for two additional surface ruptures after about ad 900, which probably correspond to the large regional earthquakes of 1063 and 1344 (or 1354). These observations suggest fairly periodic occurrence of large earthquakes (RI=c. 283±113 years) for the past millennium, and a rate of c. 16 mm/a if all events experienced similar slip. We excavated six trenches at two sites along the 1999 Izmit rupture to study the past earthquake history along that segment of the North Anatolian fault. One site, located in the township of Köseköy east of Izmit, revealed evidence for three surface ruptures (including 1999) during the past 400 years. The other trench was sited in an Ottoman canal that was excavated (but never completed) in 1591. There is evidence for three large surface rupturing events in the upper 2 m of alluvial fill within the canal at that site, located only a few kilometres from the Köseköy site. One of the past events is almost certainly the large earthquake of 1719, for which historical descriptions of damage are nearly identical to that of 1999. Other earthquakes that could plausibly be attributed to the other recognized rupture of the Izmit segment are the 1754, 1878 or 1894 events, all of which produced damage in the region and for which the source faults are poorly known. Our palaeoseismic observations suggest that the Izmit segment of the North Anatolia fault ruptures every one and a half centuries or so, consistent with the historical record for the region, although the time between ruptures may be as short as 35 years if 1754 broke the Izmit segment. Release of about 4 m of seismic slip both west and east of the Marmara Sea this past century (1912, 1999) support the contention that Istanbul is at high risk from a pending large earthquake. In that historical records suggest that the last large central Marmara Sea event occurred in 1766, there may be a similar 4 m of accumulated strain across the Marmara basin segment of the North Anatolian fault