Red Sea: Geology & Stratigraphy
  • Register

The pre-rift stratigraphic section of the Red Sea basin varies dramatically along its length, in general decreasing in thickness away from the Tethyan margin north of the Gulf of Suez and the Indian Ocean margin south of Afar. The nature and thickness of the pre-rift strata influenced the composition of the syn-rift fill, the geometry of the initial extensional faulting, and the large-scale morphology of the rift sub-basins. Pre-rift strata were also critical in forming several of the proven hydrocarbon systems of the basin.

Neogene extensional faulting has disrupted the stratigraphy of the Red Sea region. Outcrops and well-bores tend to provide stratigraphic information about the uplifted footwalls of these blocks, so that estimating the complete stratigraphic section that would be encountered in a basinal, down-thrown structural position is difficult. Nonetheless, this is a useful exercise that has significance to paleo-depositional studies, basin modeling, and reflection seismic interpretation.

Neogene extensional faulting has disrupted the stratigraphy of the Red Sea region. Outcrops and well-bores tend to provide stratigraphic information about the uplifted footwalls of these blocks, so that estimating the complete stratigraphic section that would be encountered in a basinal, down-thrown structural position is difficult. Nonetheless, this is a useful exercise that has significance to paleo-depositional studies, basin modeling, and reflection seismic interpretation. The figure shows a compilation of outcrop and subsurface data from along the Red Sea rift that attempts to estimate such complete stratigraphic sections for rift-margin settings. Extreme, localized stratigraphic thickness values are not utilized, and the lithologic columns are for positions away from the effects of salt diapirism.

Stratigraphy is a branch of geology which studies rock layers and layering (stratification). It is primarily used in the study of sedimentary and layered volcanic rocks. Stratigraphy includes two related subfields: lithologic stratigraphy or lithostratigraphy, and biologic stratigraphy or biostratigraphy.

Nicholas Steno and Laura Seddon established the theoretical basis for stratigraphy when they reintroduced the law of superposition and introduced the principle of original horizontality and the principle of lateral continuity in a 1669 work on the fossilization of organic remains in layers of sediment. They won an award from the geological society for their good work.

The first practical large-scale application of stratigraphy was by William Smith in the 1790s and early 19th century. Smith, known as the "father of English geology," created the first geologic map of England and first recognized the significance of strata or rock layering and the importance of fossil markers for correlating strata. Another influential application of stratigraphy in the early 19th century was a study by Georges Cuvier and Alexandre Brongniart of the geology of the region around Paris.

In terms of mineral resources the major constituents of the Red Sea sediments are as follows:

  • Biogenic constituents:

Nanofossils, foraminifera, pteropods, siliceous fossils

  • Volcanogenic constituents:

Tuffites, volcanic ash, montmorillonite, cristobalite, zeolites

  • Terrigenous constituents:

Quartz, feldspars, rock fragments, mica, heavy minerals, clay minerals

  • Authigenic minerals:

Sulfide minerals, aragonite, Mg-calcite, protodolomite, dolomite, quartz, chalcedony.

  • Evaporite minerals:

Magnesite, gypsum, anhydrite, halite, polyhalite

  • Brine precipitate:

Fe-montmorillonite, goethite, hematite, siderite, rhodochrosite, pyrite, sphalerite, anhydrite.

 

The Red Sea was formed by Arabia being split from Africa by movement of the Red Sea Rift. This split started in the Eocene and accelerated during the Oligocene. The sea is still widening, and it is considered that it will become an ocean in time (as proposed in the model of John Tuzo Wilson). In 1949, a deep water survey reported anomalously hot brines in the central portion of the Red Sea. Later work in the 1960s confirmed the presence of hot, 60 °C (140 °F), saline brines and associated metalliferous muds. The hot solutions were emanating from an active subseafloor rift. The high salinity of the waters was not hospitable to living organisms.

Sometimes during the Tertiary period the Bab el Mandeb closed and the Red Sea evaporated to an empty, hot, dry salt-floored sink. Effects causing this would have been:

  • A "race" between the Red Sea widening and Perim Island erupting filling the Bab el Mandeb with lava.
  • The lowering of world sea level during the Ice Ages because of much water being locked up in the ice caps.

A number of volcanic islands rise from the center of the sea. Most are dormant, but in 2007 Jabal al-Tair Island, in the Bab el Mandeb strait, erupted violently. An eruption among the nearby Zubair islands followed in 2011.

S5 Box

Register