科研之友
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摘要
Landscape formation on Cyprus is controlled by processes directly linked to the uplift and unroofing of the Troodos ophiolite complex since mainly early Miocene times. Understanding the island's geology and dating individual tectonic events will help in differentiating between tectonically controlled uplift and eustatic sea level or climatic changes. In order to improve the timing of these events, a magnetostratigraphic study was carried out on two terraces in the Mesaoria Basin of central Cyprus. At Vlokkaria, southwest of Nicosia, an artificial cliff exposes the sedimentary Apalos Formation of early Pleistocene age. A nearby section situated on a terrace, probably postdating the Vlokkaria section, was sampled at Kokkinos. Remanence-carrying minerals are end-member magnetite and maghemite formed by exsolution and oxidation from ophiolitic titanomagnetite. Hematite as a late alteration product is also present. Alternating field demagnetized paleomagnetic samples yield predominantly reversed polarities interpreted to have been acquired as early detrital remanent magnetization during the Matuyama chron. Two zones of normal polarity within the Apalos Formation are interpreted to correlate to the Olduvai and Jaramillo subchrons. Pre-Apalos marine sediments at the bottom of the Vlokkaria section show transitional polarity behavior and therefore might correlate with the onset of the Reunion event. Results from the Kokkinos section are exclusively of normal polarity, which has been acquired during the Brunhes chron. Sedimentation rates derived from these magnetostratigraphic results are in the order of 3-6 cm/kyr with a marked increase to 50 cm/kyr just below the Matuyama-Jaramillo polarity transition, which is interpreted to reflect increased uplift of the source area and supports the hypothesis of pulsed uplift of the Troodos ophiolite complex.
- 出版日期2011-1-19
