Print this pageGraphic Correlation and the Recognition of Key Stratal Surfaces and Intervals in the Sequence Stratigraphy of Miocene Rocks in the Gulf of Suez, Egypt
KREBS, WILLIAM N. , WILLIAM A. WESCOTT, and DAG NUMMEDAL
The recognition of key stratal surfaces and intervals is essential for interpreting stratigraphic sequences. Graphic correlation of lower and middle Miocene outcrops in the western Sinai of the Gulf of Suez identified four traces that represent depositional hiatuses, and the excellent exposures have revealed their nature and origins. Two of the terraces are erosional surfaces and constitute sequence boundaries sensu Vall, and the other two are associated with marine transgressions. Terraces that represent low order sequence boundaries are represented in outcrop as a single stratal surface. Each sequence boundary coincides with an abrupt change in lithology and paleobathymetry (from deep to shallow). Graphic correlation terraces associated with marine transgressions are actually comprised of several higher order hiatuses within a narrow stratigraphic (hiatal) interval and reflect high frequency sea level oscillations during long-term mare transgressions. The detection of individual brief hiatuses may be beyond the resolution of the graphic correlation technique, particularly when the composite standard was derived from well cuttings data, but the sum total of these hiatuses within a hiatal interval constitutes a graphic terrace. Ravinement and maximum flooding surfaces are present within both Miocene Sinai hiatal intervals, and one may have high order sequence boundaries or exposure surfaces in sabkha anhydrites. The hiatal intervals are characterized by numerous small scale (< 15m) and repetitive lithologic changes that reflect the transition from shallow to deeper water.