Cyclostratigraphy and chronology of the Albian stage (Piobbico core, Italy)
- 页数：130 p. :
- 第一责任说明：Alessandro Grippo.
- 分类号：a514.3 ; a511
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62h0020588 20140522141202.0 cr un||||||||| 100927s2003 xx ||||f|||d||||||||eng | CNY371.35 (UnM)AAI3116705 UnM UnM NGL a514.3 ; a511 Grippo, Alessandro. Cyclostratigraphy and chronology of the Albian stage (Piobbico core, Italy) [electronic resource] / Alessandro Grippo. 130 p. : digital, PDF file. Adviser: David J. Bottjer. ; Source: Dissertation Abstracts International, Volume: 64-12, Section: B, page: 5977. Thesis (Ph.D.) -- University of Southern California, 2003. The Mid-Cretaceous deep-water sediments (coccolith-globigerinacean marls) of the Umbria-Marche Apennines (Italy) show complex rhythmic bedding. In 1982, the Piobbico core was drilled through the Aptian-Albian Scisti a Fucoidi Formation to test the hypothesis of orbital climatic control in the mid-Cretaceous.;Early studies on the Piobbico core have been integrated in this work, through the development of a new optical technique that uses the color (reflectivity) as a proxy for carbonate and organic carbon content.;This technique was used to yield a digitized and image-processed photographic log (photolog) of the Piobbico core. From the photolog, a gray-scale scan was obtained in order to produce a continuous time-series suitable for spectral analysis.;A drab facies in the Scisti a Fucoidi is interpreted as recording normal stratified water conditions, while a red facies as the product of downwelling warm saline (halothermal) waters.;Both facies are pervaded by orbital (Milankovitch) rhythms. These reflect fluctuations in the composition and carbonate production of the calcareous plankton in the upper waters.;The drab facies is overprinted by redox oscillations on the bottom, including episodical precessional anaerobic pulses (PAPs). Contrasts between the individual beds representing the alternate phases of the precessional rhythm rose and fell with orbital eccentricity, in the classical pattern of Berger's climatic precession or precession index curve, varyingly complicated by the obliquity rhythm. According to this, greenhouse oceans in general, and perhaps this area in particular, seem to have been very sensitive to orbital forcing.;A count of 29.4 406-ky eccentricity cycles yields an Albian duration of 11.9 ± 0.4 My.;This method has also been experimentally applied, with good results, using surface exposures. Geology, Stratigraphic ; Chronology. Cretaceous. aCN bNGL http://pqdt.bjzhongke.com.cn/Detail.aspx?pid=u6q9w0XgB0E%3d NGL Bs611 rCNY371.35 ; h1 xhbs1002