2008 Joint Meeting of The Geological Society of America, Soil Science Society of America, American Society of Agronomy, Crop Science Society of America, Gulf Coast Association of Geological Societies with the Gulf Coast Section of SEPM

Paper No. 19
Presentation Time: 8:00 AM-6:00 PM

Fractal Analysis and Depositional Cycles from Stratigraphic Sequences of the Upper Cretaceous at the Iberian Range (Spain)

GIL, Javier1, GUMIEL, Pablo2, ARIAS, Monica3, SEGURA, Manuel1, GARCÍA-HIDALGO, José F.1 and CARENAS, Beatriz4, (1)Departamento de Geología, Universidad de Alcalá, Alcalá de Henares, 28871, Spain, (2)Recursos Minerales / Departamento de Geología, Instituto Geológico y Minero de España (IGME) / Universidad de Alcalá, Rios Rosas, 23, Madrid, 28003, Spain, (3)Departamento de Geología, Universidad de Alcalá, Facultad de Ciencias, N-II, 33.600 km, Alcalá de Henares, 28871, Spain, (4)Departamento de Geología y Geoquímica, Madrid, 28049, Spain, pablo.gumiel@uah.es

A fractal approach to the study of cyclicity from twenty stratigraphic sections of the Upper Turonian of the Iberian Basin is presented. The strata thickness distribution (Dt) of these sections conforms to power law distributions of the form Nt≈Ct-D, where Nt is the number of strata with thickness>t, which may be interpreted in terms of self-affine fractal scaling. Dt is an exponent related to the fractal dimension of the system, obtained from the previous equation applying logarithms.

Values of Dt obtained from the total thickness of each stratigraphic section range from 0.64 to 1.37. Dt is higher (0.8 to 1.37) in the central area of the Basin, and is lower (0.8 to 0.64) towards the southern coastal margin. These values can be considered as a parameter which reflects the geometrical organization of the 4th-order parasequences in each section.

Values of Dt ranging from 0.8 to 0.64 correspond to sections with both a wide range in bed thickness and thicker strata (around 0.4 m). Values of Dt ranging from 1.37 to 0.8 correspond to sections with more homogeneous bed thickness, composed mainly of thinner strata (around 0.2 m).

Lower Dt values reflect sections with heterogeneous accommodation within mixed terrigenous-carbonate environments. Meanwhile, those sections with higher Dt values correspond to carbonate platform environments with more homogeneous accommodation. Besides, the sections with lower Dt are more sensitive to lateral displacements of the carbonate platform facies belts (progradation or retrogradation).

These preliminary results show that fractal analysis may be a new tool of critical importance in the stratigraphic and dynamic analysis of stratigraphic successions. Fractal analysis can be utilized to get a better insight into the stratigraphical and sedimentological interpretations. It can also be used as a quality control parameter of field data, detecting sections with exposure problems.