Multi-proxy evidences of Mid-Pleistocene dry climates observed on calcretes in Central Turkey

Multiproxy Evidence Of Mid-pleistocene D TURKEY

Makale detayları

Multi-proxy evidences of Mid-Pleistocene dry climates observed on calcretes in Central Turkey

Yazarlar:

Multiproxy Evidence Of Mid-pleistocene D TURKEY

Yayıncı:

TUBITAK

Dergi:

Turkish Journal of Earth Sciences 2013 Vol.22 Issue 3, pp.469-483

Belge Tipi:

Makale

Yayın Tarihi:

2/2013

Belge Dili:

Türkçe

Document ID (Org No.):

2000731805

Sıklık:

İki Aylık

eISSN:

1303-619X

pISSN:

1300-0985

Özet:

 

Palaeosols are very important in reconstructing palaeoclimate studies, since they are accepted as useful climate markers and as potential providers of proxy data. The study of the palaeosols of the Plio-Pleistocene rock sequences around Ankara revealed evidence for a reconstruction of the Quaternary palaeoclimate of the region. The study area is located in Bala, south-east of Ankara, which contains Middle Pleistocene red palaeosols with powdery to nodular calcrete developments, alternating with channel deposits. During this warm and arid period in the Pleistocene, the limited water available in the soil led to the accumulation of low magnesian carbonates, forming calcretes. The clay fractions of the samples were X-rayed using air-drying, ethylene-glycol solvation and heating treatments. The clay mineral contents were determined as smectite, kaolinite, illite and chlorite. Palygorskite was also identified. In the relative abundances of clay minerals, smectite, the most abundant clay mineral, is depleted towards the upper part of the section while the amount of palygorskite increases. Since palygorskite is the only pedogenic mineral formed during the Pleistocene, its presence can be accepted as evidence of the dominant arid climatic conditions. The isotopic composition of carbonates in the Bala section exhibits a slightly wider range in d13C composition from -5.98%o to -9.22%o and a narrower range in d18O composition from -7.19%o to -8.66%o. The carbon isotope values clearly imply that arid to semiarid flora C4 is dominant, with C3:C4 mixed vegetation. This study suggests that the Middle Pleistocene is the time of the Mid-Brunhes Event when the dominantly warm climatic temperatures led to the development of calcretes in Bala, Ankara, as with all Quaternary Mediterranean-type calcretes.

 

Palaeosols are very important in reconstructing palaeoclimate studies, since they are accepted as useful climate markers and as potential providers of proxy data. The study of the palaeosols of the Plio-Pleistocene rock sequences around Ankara revealed evidence for a reconstruction of the Quaternary palaeoclimate of the region. The study area is located in Bala, south-east of Ankara, which contains Middle Pleistocene red palaeosols with powdery to nodular calcrete developments, alternating with channel deposits. During this warm and arid period in the Pleistocene, the limited water available in the soil led to the accumulation of low magnesian carbonates, forming calcretes. The clay fractions of the samples were X-rayed using air-drying, ethylene-glycol solvation and heating treatments. The clay mineral contents were determined as smectite, kaolinite, illite and chlorite. Palygorskite was also identified. In the relative abundances of clay minerals, smectite, the most abundant clay mineral, is depleted towards the upper part of the section while the amount of palygorskite increases. Since palygorskite is the only pedogenic mineral formed during the Pleistocene, its presence can be accepted as evidence of the dominant arid climatic conditions. The isotopic composition of carbonates in the Bala section exhibits a slightly wider range in d13C composition from -5.98%o to -9.22%o and a narrower range in d18O composition from -7.19%o to -8.66%o. The carbon isotope values clearly imply that arid to semiarid flora C4 is dominant, with C3:C4 mixed vegetation. This study suggests that the Middle Pleistocene is the time of the Mid-Brunhes Event when the dominantly warm climatic temperatures led to the development of calcretes in Bala, Ankara, as with all Quaternary Mediterranean-type calcretes.

Makale detayları

Multi-proxy evidences of Mid-Pleistocene dry climates observed on calcretes in Central Turkey

Yazarlar: Multiproxy Evidence Of Mid-pleistocene D TURKEY

Yayıncı: TUBITAK

Dergi: Turkish Journal of Earth Sciences 2013 Vol.22 Issue 3, pp.469-483

Belge Tipi: Makale

Yayın Tarihi: 2/2013

Belge Dili: Türkçe

Document ID (Org No.): 2000731805

Sıklık: İki Aylık

eISSN: 1303-619X

pISSN: 1300-0985

Sayı

Yazarlar:

Multiproxy Evidence Of Mid-pleistocene D TURKEY

Yayıncı:

TUBITAK

Dergi:

Turkish Journal of Earth Sciences 2013 Vol.22 Issue 3, pp.469-483

Belge Tipi:

Makale

Yayın Tarihi:

2/2013

Belge Dili:

Türkçe

Document ID (Org No.):

2000731805

Sıklık:

İki Aylık

eISSN:

1303-619X

pISSN:

1300-0985