Abstract

Lamb et al. (2004) identified from flume experiments four regimes of deposition, mathematically described by a Ponding Index (Po): (1) a perfectly ponded deposit, (2) a mounded deposit, (3) a perfectly draped deposit, and (4) a deposit with accentuated highs. This study extends Lamb’s laboratory results to basin scale architecture by using bathymetry, gravity, and magnetics combined with fractal geometry to predict the same four sedimentary facies in the Gulf of Mexico region.

Turcotte (1992) first published Fractals and Chaos in Geology and Geophysics 25 years ago. Data that exhibit power-law spectra, such as bathymetry, gravity, and magnetics, are suitable for the application of fractal geometry. The fractal dimension of the combination of bathymetry and gravity (FDBG) identifies a preferred depositional pattern working from the top down through geologic time. Likewise, combining magnetics and gravity with fractal geometry (FDMG) identifies a preferred depositional pattern working from the bottom up through geologic time. Taking the ratio FDBG/FDMG yields a Ratio Index (Ro) map similar to Lamb’s Po.

After 70 years of drilling in the Gulf of Mexico, many fields correlate well with Ro. The expanded Miocene discoveries (e.g., Thunderhorse) in the deepwater Gulf of Mexico are examples of ponded deposits. There are also several large mounded deposit fields (e.g., Mars). This study presents an Ro map over the Gulf of Mexico showing the four sedimentary facies identified in the Lamb et al. (2004) paper. Examples of all four depositional regimes are shown on several 2D seismic lines (GulfSPAN). The study area extends down to the Yucatan Peninsula where Ro shows a diagnostic footprint of the Chicxulub Impact. The study thus discusses other possible impact sites in the Gulf of Mexico based on Ro.