ABSTRACT: Stratigraphic Interpretation of an Area of Migiurtinia (Northern Somalia) Using Integrated TM, Aerial Photographic, Laboratory Spectral, and Petrologic Data

FERRARI, M. CARLA, MARIA SGAVETTI, and ROBERTO CHIARI, University of Parma, Parma, Italy, and PIERO L. FANTOZZI, University of Siena, Siena, Italy

Landsat TM data, aerial photointerpretation, laboratory reflectance spectra, and petrographic-geochemical analyses have been integrated to study an area of Northern Somalia. In this area, Mesozoic-Tertiary strata unconformably overlie Paleozoic metasediments. The Cretaceous to Eocene strata were deposited on a relatively stable shelf and severely affected by Oligocene-Miocene Aden rifting. Within the prerift strata, major transgressive and regressive phases characterize several formations, comprising a number of distinct lithofacies.

Specifically processed Landsat data provided a useful tool to map distinct spectrofacies units of lithologic significance and to define their areal pattern. Aerial photostratigraphic analysis provided a correlation framework with local chronostratigraphic significance. Field survey and petrographic observation on weathered surfaces allowed us to lithologically label the spectrofacies units. Laboratory reflectance spectra and petrographic-geochemical analysis gave insight into the complex physical parameters affecting rock reflectance and on TM potential to differentiate among carbonate petrofacies. This provided theoretic criteria that improved TM data interpretation.

The integration of different data sets led to frame spectrofacies units within a photostratigraphic framework extended over a wide, tectonically deformed area. This allowed the recognition of lateral spectrofacies variations within well-defined, time-significant stratigraphic intervals. Within one of these stratigraphic units, the new integrated data set points out an important relative sea level fall; this event is expressed by characteristic stratal patterns and specific spectral responses indicating silcrete and caliche horizons. This unit is overlain by a transgressive pattern consisting of supratidal evaporites and dolomite cycles, topped by open shelf deposits.

AAPG Search and Discovery Article #91012©1992 AAPG Annual Meeting, Calgary, Alberta, Canada, June 22-25, 1992 (2009)