Sedimentology, sequential analysis and clay mineralogy of the lower Eocene sequence at Farafra Oasis area, Western Desert of Egypt

Ayyat, Abdalla M. El

doi:10.1016/j.jafrearsci.2012.09.011

Cited by 17 publications

(6 citation statements)

References 31 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…These microfacies associations are equivalent to SMF 9/FZ 8 of Wilson (1975), which suggests deposition in shallow restricted lagoons of a low-energy environment. The FA-4 is closely similar to that described in the restricted inner lagoon carbonates of the Eocene rocks in different localities in Egypt (Stefan et al 2011;El-Ayyat 2013;Sallam et al 2015). In addition, the gypsifeous shale beds and the sandy shelly (Ostrea-rich) wacke/packstone facies in the lower unit of the Maadi Formation may reflect sedimentation in a restricted inner lagoon of low-energy, well-oxygenated, normal saline water.…”

Section: Discussionsupporting

confidence: 82%

“…Out of them, Khalifa (1981) described finegrained dolomite rhombs in the Lower Eocene and attributed them to contemporaneous dolomitization of limemud in supratidal flats. According to Khalifa (1996), Wanas (2008) and El-Ayyat (2013), the occurrence of fine crystalline dolomite in the platform carbonate indicates peritidal (upper intertidal-supratidal) carbonates that were formed during sea level fall. On the other hand, Tucker and Wright (1990) attributed the formation of the fine crystalline dolomite associated with gypsum crystalfilled pores to intensive evaporation of marine water in a supratidal zone during a short period of sea level fall, and a contemporaneous replacement of a previously deposited lime-mudstone.…”

Section: Discussionmentioning

confidence: 99%

See 1 more Smart Citation

Stratigraphy, facies analysis and sequence stratigraphy of the Eocene succession in the Shabrawet area (north Eastern Desert, Egypt): an example for a tectonically influenced inner ramp carbonate platform

2015

View full text Add to dashboard Cite

The Eocene rocks in the Shabrawet area (north Eastern Desert, Egypt) have been subdivided into three formations that are from base to top: the Minia Formation (Late Ypresian), the Sannor Formation (Bartonian) and the Maadi Formation (Priabonian). These three formations are disconformable with each other. In addition, the whole Eocene succession is disconformably overlain by the Oligocene rocks and is underlain by the Cretaceous rocks with an angular unconformity surface. The Sannor Formation has been subdivided into three informal units: lower, middle and upper units. The overall sedimentary nature of the Eocene rocks in the study area is dominated by carbonate-siliciclastic rocks. Detailed microfacies analysis has enabled discrimination of 22 sedimentary microfacies types, which are grouped into six facies associations, equivalent to six depositional environments sited on an inner ramp setting. These depositional environments are floodplain-dominated fluvial, lacustrine/palustrine, tidal flat, restricted inner lagoon, shoal bar and outer lagoon with open circulation. A suitable depositional model of the Eocene rocks is given. In addition, four discrete benthonic foraminiferal biozones were reported in the Eocene succession, arranged from base to top: (1) Alveolina frumentiformis biozone (Late Ypresian), (2) Orthoplecta clavata biozone (Bartonian), (3) Dictyoconus aegyptiensis biozone (Bartonian) and (4)Discorbis vesicularis biozone (Priabonian). In terms of sequence stratigraphy, the studied Eocene succession exhibits three superimposed depositional sequences, each of which shows retrogradational (transgressive systems tract) and aggradational (highstand systems tract) to progradational (lowstand systems tract) packages of facies. The retrogradational package displays a predominance of outer lagoon and restricted inner lagoon facies. The aggradational package shows an increase of shoal bar and tidal flat facies, whereas the progradational package marks the occurrence of continental facies (floodplaindominated fluvial and lacustrine deposits). In this study, it is noticed that there are lateral and vertical changes in the depositional environments of the Eocene rocks, between shallow marine and continental environments. Also, many unconformities have been recorded in between and within these rock units. Such remarks indicate that the Eocene rocks were deposited within a highly tectonically active area that was consequently influenced by the transgression and regression of the Neo-Tethys. Such tectonic activity could be related to the Syrian Arc System that was renewed and enlarged several times during the Late Cretaceous up to the Neogene in the eastern and southeastern Mediterranean domain.

show abstract

Section: Discussionsupporting

confidence: 82%

Section: Discussionmentioning

confidence: 99%

Stratigraphy, facies analysis and sequence stratigraphy of the Eocene succession in the Shabrawet area (north Eastern Desert, Egypt): an example for a tectonically influenced inner ramp carbonate platform

2015

View full text Add to dashboard Cite

show abstract

“…Limestones yield Fe and Mn contents (n = 56; mean 148 ppm and 26 ppm, respectively) that are low compare to the adjacent dolostones (Figure 10a), whilst Sr contents (mean 241) are higher (n = 56; 140 ppm; Figures 10b, c). 6c, d and 7b), typical for the Jahrum Formation, have been documented from other Eocene locations worldwide (e.g., Gaswirth et al, 2007;Salad-Hersi, 2011;Maliva et al, 2011;El Ayyat, 2013). Dolomite preferentially nucleated within and replaced microcrystalline matrix, partially replacing adjacent fossils (e.g., impingement replacement, Lucia, 1962) 2 and 3 for data.…”

Section: Major and Trace Elemental Concentrationsmentioning

confidence: 84%

Shallow burial dolomitization of an Eocene carbonate platform, southeast Zagros Basin, Iran

Zohdi¹,

Moallemi²,

Moussavi‐Harami³

et al. 2014

GeoArabia

View full text Add to dashboard Cite

Here, a case example of a dolomitized Eocene ramp setting from the southeastern Zagros Basin is documented and discussed in the context of published work. This is of significance as well-documented case examples of Eocene dolomitized inner platforms are comparably rare. The same is true for detailed diagenetic studies from the Zagros Basin in general. Three measured field sections were combined with detailed petrographic and geochemical analyses and four main dolomite types were defined. The most significant dolomite type is present in the form of a volumetrically significant occurrence of meter-thick beds of strata-bound dolostones. These dolomites are characterized by near-stoichiometric composition, fabric-retentive and fabric-destructive textures, subhedral to anhedral in shape and most being in the tens-of-microns range. Dolomite δ18O (averaging -2.6‰) values are depleted relative to that expected for precipitation from Eocene seawater (averaging 0‰), while δ13C (averaging -0.1‰) values are within the range of Eocene seawater values (averaging 0.5‰). Dolomite Type II and III 87Sr/86S values from 0.7079 to 0.7086 are somewhat elevated with respect to Eocene seawater (0.7077 and 0.7078). Based on these data, it is suggested that moderately evaporated seawater, via shallow seepage reflux, acted as agent for the initial dolomitization process. Subsequently, early diagenetic dolomites were recrystallized during shallow burial to variable degrees. The absence of volumetrically significant evaporitic deposits indicates that the salinity of porewater during dolomitization was beneath the threshold limit for gypsum precipitation. In addition, ascending saline fluids from deep-seated salt diapirs might have affected dolomitizing fluids.

show abstract

“…Geologically, the Farafra Oasis is situated close to the periphery of the cratonic domain of Northeast Africa that experienced several phases of tectonic activity during the Late Mesozoic–Cenozoic (Guiraud, Bosworth, Thierry, & Delplanque, 2005). The geology of the Farafra Oasis has been addressed in the synthetic works by Hamimi et al (2020) and Said (2017), as well as in the articles by Al‐Kahtany (2017), El Ayyat (2013), Farouk et al (2019), Hassan, Barich, Mahmoud, and Hemdan (2001), Hassan, Hamdan, and Mahmoud (2014), Ibrahim and Abdel‐Kireem (1997), Kasem, Wise, Faris, Farouk, and Zahran (2020), Khalifa and Zaghloul (1990), Plyusnina et al (2016), Wanas (2012), Wanas and Armenteros (2019), and Wanas, Abu Shama, and El‐Nahrawy (2020). These studies focused chiefly on stratigraphy, (micro)palaeontology, and Quaternary sediments.…”

Section: Geological Settingmentioning

confidence: 99%

Quaternary lacustrine dolostones of Sahara: New geoheritage evidence from the Farafra Oasis (Egypt)

2021

View full text Add to dashboard Cite

Oases of the Western Desert of Egypt host numerous geoheritage features. Field investigations in the Farafra Oasis have permitted to establish the presence of brown dolostones occurring in channels incised in the Upper Cretaceous rocks, on slopes of topographic highs, as fills of the karst features, and directly on wide depressions floor. Their origin is linked to carbonate deposition in a palaeolake that existed in the pluvial conditions of the Pleistocene. Such dolostones are rare on regional, national, and even global scales, and, thus, they constitute a high‐value geoheritage feature. The latter can be assigned to sedimentary, palaeogeographical, and stratigraphical geoheritage types. The most typical locality of these lacustrine dolostones is North Ain El‐Wadi that is proposed as a geosite. This new evidence extends the previous knowledge of the geoheritage of the Farafra Oasis. Although the main utility of the proposed geosite is scientific, this object can also be used for the purposes of geoeducation and geotourism in combination with the other geoheritage resources of the central part of the Western Desert of Egypt.

show abstract

Sedimentology, sequential analysis and clay mineralogy of the lower Eocene sequence at Farafra Oasis area, Western Desert of Egypt

Cited by 17 publications

References 31 publications

Stratigraphy, facies analysis and sequence stratigraphy of the Eocene succession in the Shabrawet area (north Eastern Desert, Egypt): an example for a tectonically influenced inner ramp carbonate platform

Stratigraphy, facies analysis and sequence stratigraphy of the Eocene succession in the Shabrawet area (north Eastern Desert, Egypt): an example for a tectonically influenced inner ramp carbonate platform

Shallow burial dolomitization of an Eocene carbonate platform, southeast Zagros Basin, Iran

Quaternary lacustrine dolostones of Sahara: New geoheritage evidence from the Farafra Oasis (Egypt)

Contact Info

Product

Resources

About