Qasr El-Sagha Formation Research Articles

Symbiosis of genus Hydractinia and in situ hermit crab in Kerunia cornuta Mayer-Eymar, 1899 from the Upper Eocene rocks in northwest Qarun Lake, Fayum area, Egypt

The Upper Eocene rocks (Qasr El-Sagha Formation) at northwestern Qarun Lake, in Fayum depression, revealed numerous abraded and bio-eroded Kerunia cornuta specimens, with calcified hydractinian encrustation. The symbiotic relationship between the encrusted genus Hydractinia and the host gastropod shell is discussed through thin section examination. A report of in situ hermit crab in the host gastropod shell in Kerunia cornuta is documented here for the first time from the Eocene rocks of Egypt. The studied bioerosion structures in Kerunia are attributed to three ichnospecies: Gastrochaenolites lapidicus Kelly and Bromley1984; Gastrochaenolites torpedo Kelly and Bromley1984 and Gastrochaenolites isp. These ichnospecies are related to Trypanites ichnofacies in an offshore environment under storm wave base. The taphonomic processes that affected the Kerunia cornuta specimens are also discussed in this work. The present study indicates that the paleoenvironment prevailed during the deposition of the Kerunia cornuta specimens reflects shallow agitated and bioturbated environments.

Geochemical and organic petrographic analyses on the Late Eocene bentonitic shale bed in Kom Aushim vicinity, Fayum, Egypt; Paleoenvironmental implications

Bentonitic shale bed of the Qasr El Sagha Formation (Late Eocene), located in the Kom Aushim area, Fayum, composes of 5 m thickness of dark massive stratum intercalated with veins of iron bands. In this study, twelve fresh shale samples from this area were investigated concerning their geochemical and organic petrography analyses. A total organic carbon (TOC) of the shale samples is very low (0.07–0.39 wt%). Petrographic analysis of samples shows a dominance of the vitrinite maceral followed by either inertinite and/or liptinite macerals. Theoretically derived vitrinite reflectance (Rocal) reveals that the bentonitic shale bed was subjected to an abnormal increase in maturity toward the invasion of Fe, Zn, Cu rich hydrothermal sulfates and oxides veins. The composition and origin of these veins were investigated by XRD and XRF analyses. The results suggested that the Fe brought from these veins affected the main composition of the shale stratum to exhibit Fe-shale facies. Moreover, rich iron in the depositional medium leads to form siderite minerals (≈10%) and the replacement of lime associated clay to Ferron dolomite (≈25%). The dominant paleoclimate synchronized shale deposition was semi-arid and arid climate, as confirmed by the domination of evaporite (≈44% gypsum). The source area of shale components was found to be sedimentary and mafic igneous (basaltic trend). CIA-ICV and A–CN–K ternary diagrams showed that the shale components were subjected to a variety of intensive to moderate weathering, and they were probably coming from gabbro and tonalite igneous rock. An active sedimentary margin and island arc are the main provinces, as the shale was deposited at the marine anoxic condition of a clay-lime platform of a pro-delta sedimentary setting. The organic matters (OM) are of type III and IIIC that refer to terrestrial OM of marginal aquatic environments. Organic and inorganic studies confirm a prevailing depositional environment of a shallow shelf, shoreline mudflats and evaporitic lagoon that reflects the general trend of sea-level regression in the Fayum area during the Late Eocene.

The effect of early Priabonian sea-level change on the depositional architecture of the lower Qasr El-Sagha Formation, Kom Aushim, NE Fayum, Egypt

The vertebrate fossil-bearing upper Eocene strata in the Fayum area, Egypt exhibit complex lateral facies variations making their stratigraphy and depositional setting a matter of debate. They are exceptionally well exposed in the Kom Aushim Quarry region, NE Fayum, where they have hitherto been rarely studied. A recent study in a nearby locality had imposed a tide-dominated delta for these strata. The present study provides insight into this sedimentary succession and introduces an updated sedimentological interpretation of the Umm Rigl Member; basal Qasr El-Sagha Formation relying on outcrop facies analysis and sequence stratigraphic data. Eight short stratigraphic sections were measured and fully described in terms of lithology, grain size, stratal boundaries and sedimentary structures. The mud-dominated lower unit of the Umm Rigl Member consists of four vertically stacked shallowing/coarsening upward bay-margin/lagoonal deltas. The strata in the upper unit of the Umm Rigl Member are interpreted as incised valley back infilled with fluvial, upper estuary, tidal flat passing upwards into shallow and open marine deposits. The strata represent two incomplete depositional sequences, separated by a sequence boundary defined by an abrupt basin-ward shift of facies and equates with the base of incised valley previously recognized in Wadi Al-Hitan area. This boundary may equate with the early Priabonian Pr-2 global sea-level fall. Based on transgressive stacking of facies, the strata of the upper unit are interpreted as estuarine rather than deltaic system. This updated interpretation enhances understanding of depositional history and the paleogeographic evolution of NE Fayum during the late Eocene.

Oldest Record of African Bagridae and Evidence from Catfishes for a Marine Influence in the Late Eocene Birket Qarun Locality 2 (BQ-2), Fayum Depression, Egypt

ABSTRACT The Birket Qarun Formation, sampling upper Eocene deposits of the Fayum Depression, has been the subject of disagreement in terms of the environmental deposition. The formation has traditionally been considered to be a marine deposit but, more recently, one particular site, Birket Qarun Locality 2 (BQ-2), has been reported to have freshwater vertebrates, indicating that at least this locality in the formation contains terrestrial deposits. We here report a new varied assemblage of fossil catfishes from BQ-2, which adds new information with which to interpret the paleoenvironment of the locality. The new BQ-2 catfish assemblage includes the earliest record of the freshwater family Bagridae in Africa, as well as the oldest records of Fajumia and Socnopaea, otherwise known only from the overlying marine deposits of the Qasr el-Sagha Formation. Notable among the finds are remains of Arius fraasi and two additional species of marine ariid catfishes, representing the first such occurrences from the Fayum deposits. These occurrences indicate that BQ-2 likely had marine influences, or perhaps that Fajumia, Socnopaea, and Arius were euryhaline. In addition, the freshwater families Claroteidae and Mochokidae are represented among our collection. The new material documents the presence of a variety of taxa, and in addition it documents the variation in body size of members of the same family. Most evidence from other vertebrate fossils indicates that BQ-2 is a freshwater deposit, but some elements of the new catfish collection suggest the presence of nearshore marine influences, indicating that a much more complex environment was present.

Sclerobiont assemblages on the late Eocene bivalve Carolia placunoides: Composition, distribution and their paleoecological significance

Here we describe the composition and distribution of sclerobionts on the late Eocene bivalve Carolia placunoides and provide information about its paleoecology. More than 250 shells were collected from the Temple Member of the Qasr El-Sagha Formation exposed in El-Fayum Province. Nine ichnogenera have been recorded including Gastrochaenolites, Maeandropolydora, Caulostrepsis, Entobia, Centrichnus, Belichnus, Anellusichnus, Oichnus and Trypanites. The dense population of borings made by boring bivalves, Gastrochaenolites, is the most remarkable. Encrusters include serpulid worms (Spirobranchus cf. luxata), balanoid barnacles, and oysters. Shells of juvenile Carolia were the most dominant encrusters. Sclerobionts occurred on left and right valves; they apparently favoured the interior surfaces on both valves but they preferred no special sites. The Carolia placunoides shell concentration is interpreted as para-autochthonous assemblage.

Depositional environment and characteristics of Late Eocene carbonaceous swampy tidal flat facies in the Fayoum Basin, Egypt

This study addresses the stratigraphic and sedimentological characteristics of the Late Eocene carbonaceous shale-bearing Qasr El Sagha Formation in the Fayoum Basin, Egypt. The Qasr El Sagha succession is comprised of four facies types: coastal mudflat, tidal flat, swamp, and storm-affected tidal channels. The swamp facies contain the Fayoum carbonaceous shale facies, which have not been studied in the past. The present study reports the first publicly available sedimentological, palynological, and geochemical results for the Fayoum facies. Eight samples of the sequence were taken from a freshly exposed road cut and analyzed petrographically, geochemically, and palynologically in order to determine the paleoenvironment of deposition and prevailing conditions. The palynomorph assemblages show that the lower part of the sequence was deposited in a lowland-riparian environment with continued freshwater influx. The depositional regime in the upper part of the sequence was swampy and dominated by fresh water. Mixed angiosperms and pteridophytes dominated the woody forest vegetation and were the source for the formation of the Fayoum carbonaceous shale facies. The recovered palynomorph assemblage points to the prevalence of a tropical to a sub-tropical, warm, humid climate with heavy precipitation in the lowland, swampy areas that were in close proximity to the freshwater influx. The water table was above the fen surface, preventing oxidation of the vegetation. Intermittent flooding or fluctuation in paleo-water levels likely occurred in the peat paleo-mire. The Fayoum samples have Ro,ran values of ~0.40–0.50%, which is in very good agreement with the Tmax from Rock-Eval pyrolysis. Although a few of the samples have elevated S2 (15–24 mg HC/g rock) and HI values (125–140 mg HC/g TOC), they do not have any hydrocarbon generating potential in the sampled location as a result of their immaturity. Petrographically, the analyzed samples are dominated by huminite group macerals (up to 77%), with telohuminite (eu-eulminite B) being dominant. Liptinite content is up to 3.5%, whereas inertinite content is up to 6%, dominated by fungal sclerotia (funginite). The TOC of the facies samples does not exceed 40 wt%.

On the Eocene mangroves of Wadi Al-Hitan World Heritage site, Fayum, Egypt

Wadi Al-Hitan is the first site in Egypt to be inscribed by UNESCO on the “Natural World Heritage List”. Wadi Al-Hitan mangrove plant bed lies in late middle Eocene (Bartonian) at the top of Birket Qarun Formation, underlying Qasr El-Sagha Formation (Priabonian). Plant fossils include casts of roots and rhizomes, an impression of a leaf and petrified drift woods. Problematic fossils include directly–preserved hard parts of Echinodermata and casts of closely-spaced, mineral-filled siphons of bivalves. All fossils are described, illustrated and discussed in detail.

Paleontology, paleobiogeography and paleoecology of Carolia-bearing beds from the Late Eocene rocks at Nile-Fayum Divide, Egypt

The Paleontological study of the Carolia-bearing beds in (Qasr El-Sagha Formation) at Nile-Fayum Divide reveals the presences of thirteen species (three gastropods, six oysters and four Carolias). The paleobiogeography of these fauna indicates that genus Carolia Cantraine, 1838 was first recorded from the Lower Eocene of Egypt and Indian-Pakistani Region and spread out throughout the Tethyan province, West Africa and North and South America and its last occurrence was in the Early Miocene of North America. It shows also that, the first appearance of Ostrea (T.) multicostata (Deshayes, 1832) was in the Paleocene of Tunis and Algeria, and spread during the Eocene into India, northwestern Europe and the entire northern African regions. However, Cubitostrea (Cubitostrea) cubitus (Deshayes, 1832) was first reported in the Middle Eocene of France and spread to Texas in North America and North Africa. The statistical study on genus Carolia indicates that the distance between the byssal muscle scar and the retractor muscle scar increases with the increase of the left valve convexity. The paleoecological study of these faunal groups shows that, the predation and the parasitic elements as well as the stress environmental factors, caused the extinction of genus Carolia at the end of Late Eocene in Egypt.

Lithofacies and biofacies characteristics and whales skeletons distribution in the Eocene rock units of Fayoum Area, Egypt

At Wadi Al Hitan area, rapid lateral and vertical variation is observed among the exposed middle and upper Eocene rock units. The tradionally known formations (Gehannam, Briket Qaroun, Qasr El-Sagha formations) interfinger laterally and not chronologically stacked above each other in most areas. Fine siltstones and claystones characterize the Gehannam Formation, sandstones and calcareous sandstones are characteristic for Briket Qaroun Formation, dark gray claystones are attributed to Garet El-Naqb Formation and interbedded claystones are attributed to Qasr El-Sagha Formation, irrespective of their stratigraphic position. Within these formations large numbers of marine vertebrate and invertebrate fossils exist at different stratigraphic levels. Whales are classified into four species belonging to four genera, these include Basilosaurus isis, Dorudon atrox, Saghacetus Osiris and Anclacetus simonsi. Basilosaurus isis and Dorudon atrox are the most common whale species exist in these formations. No major break in sedimentation has been described within the Eocene formations in Fayoum region. Only a well marked low sea stand is indicated at the top of the Gehannam Formation where it overlain by Birket Qaroun Formation.

Eocene stratigraphy of the Wadi Al-Hitan World Heritage Site and adjacent areas (Fayum, Egypt)

The middle and late Eocene stratigraphy and depositional environments of the Wadi Al-Hitan area, Egypt, are described in detail for the first time. Complex facies relationships have been resolved by detailed logging of key sections over a 300 sq. km area and by biostratigraphic analysis. Mid and outer neritic marls and argillaceous limestones of the lower Gehannam Formation are overlain proximally by a major coastal sand body complex, the Birket Qarun Formation, which (as preserved) was deposited almost entirely on the lower shoreface. The sands of the Birket Qarun Formation prograded progressively northwards in four phases, with individual sand bodies separated by transgressive wedges of inner to mid-neritic silts and clays (the upper Gehannam Formation and the newly named Garet El-Naqb Formation). The final phase of progradation was terminated by the transgressive lower Qasr El-Sagha Formation. Calcareous nannofossil Zone NP17 (late Bartonian) is represented in the lowest Gehannam Formation. The Dictyococcites erbae nannofossil acme, previously recorded from Italy and ODP sites, has been identified at a higher level within the lower Gehannam Formation. Its start (in early NP18) is suggested as an excellent criterion to define the base of the Priabonian. Zone NP18 is highly condensed; sedimentation rates increased dramatically in early NP19/20 with the shift to predominantly clastic sedimentation. The Birket Qarun Formation is entirely within Zone NP19/20 (Priabonian). Seven depositional sequences are tentatively differentiated. Previous sedimentologic and paleogeographic interpretations are discussed; there is no evidence for ‘bay’ or otherwise restricted environments within this area, and previously proposed episodes of emersion are also discounted. Levels with relatively abundant marine mammals mainly reflect episodes of reduced clastic sedimentation, but are partly biased by differing surface exposure of successive intervals. There is no evidence that these levels represent whale ‘calving grounds’, or that marine mammals were unusually concentrated in this area in life.

Identification of basilosaurid archaeocetes (Mammalia, Cetacea) collected in Egypt by Richard Markgraf (1901–1916)

Chicago Field Museum FMNH P-12343 includes a cranium and dentary of a late Eocene archaeocete whale. These were acquired from the commercial fossil dealer Friedrich Kranz of Bonn in 1914–1915, after being collected by Richard Markgraf in Fayum, Egypt. Both were regarded as a single specimen identified in museum records as Prozeuglodon osiris. However, the cranium and dentary differ in preservation and in size, and cannot be parts of the same individual specimen nor belong to the same species. Comparison with other Fayum archaeocetes indicates that the cranium is Stromerius nidensis from the Qasr el-Sagha Formation, and the dentary is Dorudon atrox from the underlying Birket Qarun Formation. Fossils collected by Markgraf are found in museums all over the world, but he was neither a paleontologist nor stratigrapher, and identifications and ages of fossils he sold commercially cannot be accepted uncritically.

Depositional evolution of the Middle-Upper Eocene rocks, Fayum area, Egypt

The Middle-Upper Eocene rocks of the Fayum District are represented by Gehannam, Birket Qarun and Qasr El-Sagha formations. Both field studies and laboratory analyses on the concerned rocks have enabled to distinguish six lithofacies: (1) sheet-like grey silt-shale, (2) large-scale trough cross-bedded sandstone, (3) successive varicolored mud-shale/siltstone intercalation, (4) dark grey to black mud-shale/sandstone intercalation, (5) thinly bedded sandstone-shale intercalation and (6) very large-scale cross-stratified sandstone. These lithofacies proved that the present rocks were deposited in transitional paralic environment of active northward-prograding deltaic subenvironments contemporaneous with rabid but gradual sea level drop. The depositional system started with the delta front silt-shale (Gehannam Formation) of 20 m thickness, followed by distributary mouth bars of cross-bedded sandstone (Birket Qarun Formation, 50 m thick). Both the lower and upper delta plains attain thicknesses of 99 and 38 m, respectively, and are represented by the lower part of Qasr El-Sagha Formation. The deltaic sequence is topped with 45-m-thick eolian sandstones representing the upper part of Qasr El-Sagha Formation. This unit represents an extensive desertification phase that closes the depositional history of the succession examined.

Late Eocene and early Oligocene teleost and associated ichthyofauna of the Jebel Qatrani Formation, Fayum, Egypt

Fishes from the late Eocene and Oligocene Jebel Qatrani Formation of the Fayum, Egypt, have been collected for many years, but have not been extensively studied. Collections from various sites in the formation, predominantly representing riverine and shallow lake deposits, include remains of several fishes not known previously. The teleost fishes from these collections [representing Characiformes, Siluriformes, Cichlidae, Latidae (= Centropomidae), and Channidae] include species that are similar to those found in the older, underlying, Qasr el Sagha Formation (catfishes), as well as species of fishes previously unrecorded from the Fayum (cichlids and latids), or even from the Tertiary of Africa (channids). It has been suggested that the Jebel Qatrani Formation represents an area of swampy rivers with overgrown banks and floating vegetation and at least one small lake. The fish remains support this reconstruction of the palaeoenvironment, and further indicate that open riverine habitat was also probably available.

Origin of Giant Calcite-Cemented Concretions, Temple Member, Qasr El Sagha Formation (Eocene), Faiyum Depression, Egypt

ABSTRACT The Temple Member of the Qasr El Sagha Formation contains spheroidal calcite-cemented concretions in sandstone ranging from 70 cm to 9 m in diameter, although most are 1 to 4 m in diameter. Most concretions are solitary, oblate spheroids, but some are prolate, coalesced (joined laterally), or are compound (enclose smaller concretions). Half the concretions have domains with a fairly uniform center-to-center spacing of 4-6 m, but half have domains of random spacing (both clusters and segregated concretions) or occur in parallel rows of coalesced concretions. Miocene marine carbonate shells, now preserved only inside concretions, were the source of calcite cement as further supported by carbon and strontium isotopic signatures of cement (13C = -2 to +1o/oo PDB; 87Sr/86Sr = 0.70765 to 0.70770). Concretions formed at shallow burial depths in meteoric pore water (most 18O values of calcite are from -4o/oo to -2o/oo PDB) at temperatures probably between 10 and 20°C. Spheroidal, uniformly spaced concretions formed where carbonate shells were uniformly distributed and where nucleation sites were influenced by low carbonate saturation levels and widely spaced sites, or at sites established by some self-organization process; concretions in orthogonal rows in the plane of bedding probably formed where shells were concentrated during deposition; randomly spaced concretions formed where shells were unevenly spaced or where nucleation of concretions was rapid. Some Temple concretions reached exceptional size in less than 20 My owing to a combination of conditions: large initial aragonite and Mg-calcite shell concentration, widely spaced concretion growth sites locally, presence of a stable hydrologic regime over a long period of time, and possibly bacterially mediated precipitation of calcite.

Oligocene age of the Gebel Qatrani Formation, Fayum, Egypt

Abstract Sea level sequence stratigraphy is especially valuable for correlating marine stages on passively subsiding continental margins. The continental Gebel Qatrani Formation in Egypt is separated from the underlying marine Qasr el-Sagha Formation by a major unconformity with a minimum of 76 m of section missing due to erosion and/or non-deposition. This unconformity is constrained by Priabonian planktonic foraminifera in the Gehannam Formation to be younger than early late Eocene and it is constrained by radiometric ages and a great thickness of Gebel Qatrani Formation to be older than late Oligocene. The only type-1 sequence boundary within these age constraints that involved a low enough sea stand to explain the unconformity was at the Priabonian-Rupelian (Eocene-Oligocene) boundary, which means that the Gebel Qatrani Formation is entirely Oligocene in age. This corroborates earlier age assignments based on invertebrate and vertebrate faunal succession and it is consistent with new paleomagnetic evidence. The Gebel Qatrani Formation has yielded the earliest primates of anthropoid grade and the evolutionary emergence of higher primates may be related to profound environmental change during the Eocene-Oligocene transition.