Publication Date

2010-01-01

Availability

Open access

Degree Type

Thesis

Degree Name

Master of Science (MS)

Department

Marine Geology and Geophysics (Marine)

Date of Defense

2009-12-11

First Committee Member

Gregor P. Eberli - Committee Chair

Second Committee Member

Mark Grasmueck - Committee Co-Chair

Third Committee Member

Jeffrey Lukasik - Outside Committee Member

Fourth Committee Member

Brita Graham-Wall - Outside Committee Member

Abstract

Comprehensive fracture assessment is not an easy task as most fracture analyses rely on two-dimensional outcrops. A newly developed acquisition system of full resolution 3D Ground Penetrating Radar (GPR) and subsequent migration of the data allow, for the first time, to image fracture and deformation band networks in three dimensions. A full resolution GPR data set was acquired in the Madonna della Mazza quarry in the Maiella mountains, Italy. The quarry is cut into the Upper Cretaceous (Maastrichtian) Orfento Formation in the limb of an anticline. Combining 3D GPR and outcrop analysis reveals both the sedimentology and fracture characteristics in the quarry. The GPR data images the strata in more detail than what is visible in the quarry walls. For example, GPR data reveal a series of prograding bedsets that are interpreted as sub-aqueous dunes resulting from a unidirectional bottom or tidal current in the outer ramp environment. A fine-grained carbonate, lithofacies B, appears intermittently throughout the whole strata. In the massive grainstone beds extensive bioturbation destroyed the sedimentary structure and prevents the interpretation of the depositional process. The fracture development in the quarry is partly stratigraphically controlled. Deformation bands preferentially occur in the high porosity and high permeability massive grainstone unit, while stylolites are extensively developed in the thin-bedded packstone-grainstone lithofacies. The fracture analysis in the GPR data corroborates results of the outcrop analysis of previous workers. Performing a manual interpretation of the GPR data, faults with two dominant orientations (N-NW and E-W) were identified. The automated "Ant Tracking" analysis of the GPR data, however, revealed four dominant fracture orientations (N-NW, NW, W-NW, and EW). Furthermore, the automated ("Ant Tracking") 3D GPR analysis reveals a mechanical unit boundary; lithofacies C contains almost twice the density of deformation bands as the strata below. Integrating the outcrop analysis with the automated analysis of the 3D GPR data using "Ant Tracking" is essential for accurately quantifying the entire fracture population in the quarry. Total fracture diversity and abundance has previously been underestimated by 2D outcrop mapping and is also not completely depicted using manual interpretation of 3D GPR data.

Keywords

Deformation Band; Mechanical Stratigraphy

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