Digma formation

Safra member

Rock types

Uniform fine-grained limestone- marly limestone.

Diverse and multi rock types; phosphorite, chert, sandstone, dolostone, shale, porcelanite, coquinoidal and fine grained limestone types.

Rock colors

Gray to black

Multicolors range from creamy yellow, gray and black in subsurface only.

Fossil content

Planktonic and benthonic foraminifera, characterized by low diversity (bulimindea or siphogernoides rich units)

Macrobenthonic, vertebrate bones and teeth, basinword microforaminifer, sponge spicules and diatoms

Marker beds

Bulimindea and siphogerioniedes beds

Oyster beds and spongy rich porcelainite, as well as phophorite (fish teeth and bones)

Trace fossil


Burrows and borings of Thalassinoides tidal type.

Sedimentary structure


Oyster or coquina band rich buildups barriers, occasionally crossbedded oyster framestone and sandstone.


Limestone of high diversity and low diversity cycles.

Transgressive-Regressive cycles with shallowing upward cycles, locally with subareial-hard ground exposure surfaces.

Current types

Turbidity dominated

(storm local )

Tidal storm dominated

(turbidity local)


Calcite with minor clay minerals, quartz and apatite.

Calcite, dolomite, apatite, opal-CT, quartz, gypsum, anhydrite, halite as well as clay minerals

Clay mineral assemblages

Illite/Smectite-Illite assemblage, locally kaolinite.

Palygorskite-sepiolite-montmorillonite assemblage. (Kaolinite abundant in Gaara and south H3 shoreward facies)




Authigenic silicates


Zeolite and feldspar


Limited dolomitization, silicification

And locally microspartization.

Phosphatization, Dolomitization silicification, recrystallization and sparite cementation.

Basin controlled

High tectonic activity

Relative sea level fluctuations and low tectonic effect.

Upwelling currents

Weak, carbon rich facies association

Strong, Si-P-C facies association

Sedimentary environment

Open deep shelf to semi restricted graben basin type.

Coastal (locally fluvial input), inner-outer-ramp.