Category | 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 | Absent | Burrows and borings of Thalassinoides tidal type. |
Sedimentary structure | Absent | Oyster or coquina band rich buildups barriers, occasionally crossbedded oyster framestone and sandstone. |
Cycles | 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) |
Mineralogy | 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) |
Glauconite | Abundant | Absent |
Authigenic silicates | Absent | Zeolite and feldspar |
Digenesis | 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. |