Overview of the Sedimentology Diagenesis Stratigraphy and Paleontology of the Lower Cretaceous Rock Sequence in Lebanon: Focusing on Valorizing Lebanon's Natural Resource

Overview of the Sedimentology Diagenesis Stratigraphy and Paleontology of the Lower Cretaceous Rock Sequence in Lebanon: Focusing on Valorizing Lebanon's Natural Resources

George S.G. Bellos

Masters Degree Holder in Geology, and Archeology, and MBA in Management
Educational Leqdeship and Managemeny Graduate Student, 

Lebanese International University

Saloumi Road, Lebanon

Abstract: This review of the reseqrch is based on the abstract I initially presented at the 2010 AAPG ICE Meeting in Calgary. Yet, I am updating my research to integrateissues of valorizing natural resources, as in the last years, articles were published about how can Lebanon valorize both itys natural and its cultural resources to imrpove its ecomomic activity. This 2018 article discusses how Tyre city handled this. My 2020 article dicusses the pcture in Beirut city. Both cities delqt with this differently and the bottom line is that Lebanon manages its cultural and natural assets quite poorly. Yet, in terms of discussing Lebanon's main natural resource, Hydrocarbons, we should not ignore the avalability of fresh Groundwater wells offshore Lebanon. Recent petroleum prospects are discussed in this article. 

The Neocomian-Barremian “Grès de Base” or Chouf Formation, the only main Formation to be properly studied in this time period in the region, interacts with two improperly studied underlaying and overlaying carbonate strata (source). This study also aims to provide a detailed stratigraphic account of the entire Lower Cretaceous in Lebanon, by state of the art petrographic and mineralogic analyses of these rocks. It was demonstrated that the Chouf Formation was deposited in both aquatic and eolian environments. Still to be evidenced, are the strata cyclicity in the sandstone strata as well as the presence of shallow water carbonates in the Lower Cretaceous (source).

Lithostratigraphic and petrographic analyses revealed that the Neocomian-Barremian outcrops include distinct aquatic and eolian facies. These petrographic analyses described the organic rich layers in the aquatic dominated sandstone facies, but should also determine those found in the limestones In the clastic beds, the kerogens resulted in corrosion and dissolution of the quartz grains increasing the porosity/permeability of the bulk rocks upon initial hydrocarbon migration and later on the telogenic flushing with meteoric waters. A similar case should be observed for the preserved bitumens in the carbonates. Thus, this will enable us to study also the petroleum prospects of the Lower Cretaceous rock sequence as well as providing a proper sequence stratigraphic analysis of this period (source). 

Foreword: In Lebanon, the entire Lower Cretaceous is reviewed (Figure 1). Generally, it was found to be a period of regressions at the base, gradually returning back to transgressive cycles (Dr. Chris Walley's work). Samih Ukla indicated that most, if not all of these formations thin out in a W-E direction (source). The first sequence is the Upper-Tithonian to Mid-Berriasian Salima Formation (Fm). It generally comprises oölitic grainstones, which are often yellowish-ochre in color and compact (see: Louis Dubertret's Geological Maps), as this period is known to be a hiatus (source). The Sulaiy Fm of Eastern Arabia is of similar age (source). The second sequence is the Neocomian-Barremian Chouf Fm (Figure 1). It comprises three main units of sandstone strata that have been analyzed in details (source). Globally, it is an immature sandstone with roughly 7% clay content of Wealden age (e.g. Wealden-sandstein).

The third sequence is the Abeih (Jeita) Fm. It mainly contains costal carbonates showing pisolitic limestones with fossils at its base – showing the gradual transition from a more sandy to a more marine sedimentation (Figure 1) – to more oölitic, detrital, or subreefal carbonates that were dated to the Barremian based on the presence of charophytes (source). The fourth sequence is the Mdairej (Jezzine) Fm (Figure 1). It is composed of white compact cliff-forming subreefal limestone beds traceable almost everywhere. It also shows orbitolinid fossils in its topmost strata, which appear steeped (source). 

The fifth sequence is the Hammana Fm. It comprises alternations of marls and thinly bedded limestones showing abundant internal mussels as Cardium; Orbitolina (see: Dr. Chris Walley's work, and Figure 1B). Some recurrence of ferruginous sandstones and oölitic ferruginous concretions were reported in these strata. Above that begins, with a arked contrast, a succession of alternating greenish marl and limestone beds of 1–2m thick – displaying typically Albian fauna. They grade without break to the Cenomanian deep-water carbonates (see: Louis Dubertret's Geological Maps and, Dr. Chris Walley's work).

Fossil studies were quite poor in the area, and proper studies in paleontology are lacking to this day. However some accounts were given by various authors, and detailed in Dr. Chris Walley's work. Hence, the purpose is to modernize and update all these data in order to provide a better sequence stratigraphic scheme for the Lower–Cretaceous, with proper hydrocarbon assessment. Hence, analyses of our strata with PetroMod should be conducted, as with the Tithonian-Valanginian Sulaiy Fm of Eastern Arabia (source). 

Purpose of Research: Dr. Chris Walley's tectonic scheme presents the various deformations affecting the geologic sequences (Figure 2). This mainly focuses on the tectonics and structures of Syria. The Syrian Arc Deformation, (related to the Palmyrides Basin) and the Dead Sea Fault System (DSFS) are the main causes of tectonic activity in the region. The lithostratigraphic and petrographic analyses carried out from my Master's thesis (source) revealed that the Chouf Formation includes five distinct facies. Using XRD analysis the different mineral constituents were segregated and utilized to interpret the reservoir potential, as below:

• Clay rich strata (or clays) are very poor reservoirs or even seals (source).

• Carbonates (with clays) are also poor, in spite of the presence of mouldic porosity and/or unconnected pores, as they theoretically do not transmit fluid (source).

• Immature sands and greywacke are also poor to very poor reservoirs (source). Bulk mineralogy shows the presence of 5-15% to more than 15% clay content, respectively (and might include chlorites, glauconites (indicator of marine setting) and/ or other indicators of maturity such as feldspars, like in the case of arkose).

• Submature sands show some reservoir properties (source). Bulk mineralogy studies show the presence of some clay and they also tend to act as poor reservoirs (source).

• Arenites are technically good reservoirs/aquifers with high theoretical porosity (see: Mr. Mohammad Hamzeh's work). Bulk mineralogic studies point out low to very low clay content. 

This data can be very useful in attempting to answer the current (or recent) questions about the petroleum prospects of Lebanon (source), namely characterizing our potential carbonate, or other reservoir rocks, (e.g. as found by Bijan Shaheed (that for some may act as impervious seals or traps) in the case of the type I/II asphalts of the Chekka Fm), that can be achieved by correlation with other Mesozoic major clastic reservoirs (e.g. Levant, Egypt, Arabia, Persia, etc…). The Nubian, Ruthabah and Hathira Fm’s are such examples (source).

Interpretations and Discussions: The Chouf Sandstone is one of the key units of Lebanese Geology (source). It is represented by the presence of clays, iron oxides, amber, plant remnants and maybe volcanics in its lower/ upper parts (source). Some evidence pertaining to mesozoic basalts amonh other volcanics are disussed in this research. Evidence of flooding or marine influence can be evidenced by clay draping as well as liesegangen (Dr. Rudy Swennen, Personal communication, 2005), and glauconitic horizons (source). The Chouf Fm is dated to the Hauterivian/Wealden age (source) where mostly arenites have been deposited, sandwiched between 2 clay rich strata and some limestones, hence acting as an aquitard, due to the amounts of sands and clays (source). However water is still stored and transmitted, but not to satisfy exploration demands (See: Mr. Mohammad Hamzeh's work).

The paragenesis and burial history of the Chouf-Abeih Fm’s are shown in Figures 3-5 (source). The resulting pyrolysis results point out that the metamorphosed bitumens transformed to plant type kerogens (see: Figures 3-5). The sudy demonstrated  demonstrated that the pyrolysis of the Chouf Fm data reveal that the Lower Cretaceous bitumen – containing lignite (of low HI and high TOC values) – were improperly matured to kerogens, with temperatures barely reaching the oil-window (source).

Therefore, the Salima, Chouf and Abeih Fm’s need more study (and will possibly be discussed in a research paper, reading this article is a good start, and then, this one). Establishing good contacts and proper sequence stratigraphy will be a good start. With that, proper dating, and detailed hydrocarbon studies should follow. Thus, in the current study, 1) establishing ground contacts for the Salima-Chouf and Abeih Fm’s, 2) detailed sequence stratigraphy, 3) dating and paleontologic identification, and 4) proper hydrocarbon potential should be assessed. It is also expected, provided the available means permit, to study these basins in details with petroleum software, such as PetroMod and others, depending feasibility (source). Some information on petroleum prospects is provided by this research abstract and this research article. However the petroleum prospectivity in this region was known since the mid-1950s according to this article. According to this article, in the late 1970s, the petroleum prpespects in Lebanon were revised. Based on this article, four decades ago,  and to the  and in the last three decades based on this AAPG article. Yet, the Lebanese authoritites, a decade ago, considered bidding rounds based on this article. This is an asset, and in considered one of Lebanon's major natural resources (source).

Yet, if we utlized it properly, or fructified, based on the Interview by Mr Carlos Ghosn in Januqry 2021, it is what we do that counts with the assets, as possessing them only qand leaving them dormant will not be beneficial. Nevertheless, major natural resources like hydrocarbons may provide more geopolitical instability in already sensitive areas, as this AUB thesis points out. Whereas, in a world going towards sustainability (and focusong on SDGs), this other AUB thesis could be a good read.

Figures: These figures are those referred to above, in the text (source):

Figure 1 A: Revised Stratigraphy of the Lower-Cretaceous of Lebanon (source). D4 and V4 refer to Albian activities (source)

Figure 1 B: Albian incised valley at Beit Monzer, near Ehden, in northern Lebanon (source) showing disconformities (D1-4). Only the lower Cretaceous beds are affected; the Knemiceras marls (upper Hammana Fm) and the upper Albian platform carbonates (Sannine Fm?) rest conformably over everything (source).

Figure 2: Simplified tectinic map, initially proposed by Dr. Chris Walley. It shows the two major tectonic features that affect the Levantine margin: The Syrian Arc Deformation (Mid Eocene) and the Dead Sea Fault System (DSFS Miocene).

Figure 3: Sequence of diagenetic phases for the sandstone facies exposed in Lebanon (cf. Bellos, in press). Aren. = arenite, O.M. = organic matter, Qtz. = quartz, Lit. = lithification, Telog. = telogenesis, and Oxid. = oxidation (source).

Figure 4: Sequence of diagenetic phases for the limestone facies exposed in Lebanon (cf. Bellos, in press). O.M. = organic matter, Prim. = primary, Dissol. = dissolution, sol. coll. = solution collapse, arag. = aragonite, Telo. = telogenesis, and Oxid. = oxidation (source).

Figure 5: Burial curve with recorded diagenetic history of the Chouf Fm (source). Note the recorded burial estimation is estimated at 188 m, thickness is 300 m, and the resulting curve is uncorrected for compaction (Creta. = Cretaceous, Pli. = Pliocene, T. = Recent, and O.M. = Organic Matter). Based on this, the pyrolysis results were estimated, and will be further exposed herein (source).