Characterization of the Lebanese Jurassic–Cretaceous carbonate stratigraphic sequence: a geochemical approach

Abstract

The Lebanese crustal segment is part of a much larger carbonate platform deposited along the northwestern margin of the Arabian Plate, in the eastern Mediterranean region. It is made up mainly of Jurassic–Cretaceous carbonate rocks. Most of this stratigraphic sequence is exposed in the Nahr Ibrahim canyon and surrounding areas in central Lebanon. The various formations, from the oldest unit (the Lower Jurassic Kesrouane Formation) to the Upper Cretaceous Chekka Formation, are made up of different types of carbonate rocks including micritic limestone, medium‐ to coarse‐grained dolostone, biomicritic (chalk), biosparrudite limestone, micritic dolostone, pelmicrite, marl and marly limestone.Results of this first chemical investigation on the Lebanese carbonate platform show that the micritic limestone of the Kesrouane Formation is relatively enriched in Ca, Na and Sc, and has low rare‐earth element (REE) contents. The marl units of the Hammana Formation are enriched in Al, Fe, K, Ti, Rb, Ga, Nb, U, Th and REE. The chalk of the Chekka Formation shows the highest phosphorus content. A significant increase in P and Sr contents with time (from the Lower Jurassic to the Upper Cretaceous carbonate units) characterizes the Lebanese sequence; this is interpreted to be related to a possible increase in continental weathering rates during the Mesozoic. Enrichment in Ni, Ti and Nb in some formations is interpreted to be linked to Mesozoic volcanism in central Lebanon. The Cretaceous formations are subdivided according to their REE patterns into two distinct groups: limestones (Mdairej, Sannine and Maameltain formations) which are depleted in REE; and marl/chalk (Hammana and Chekka formations) which are significantly enriched in REE. On several geochemical variation diagrams, such as the K–Ti–P triangular plot, the Lebanese Mesozoic carbonate formations are found to occupy distinct compositional fields. Thus, carbonate geochemistry could prove to be a powerful tool (especially when combined with petrographic data) in characterizing and correlating carbonate formations (chemical stratigraphy), particularly in regions where field evidence may be limited. Results of this study have significant implications for the entire carbonate platform that covers a large part of the eastern Mediterranean region. Copyright © 2002 John Wiley & Sons, Ltd.

Mercury Distribution and Methylmercury Mobility in the Sediments of Three Sites on the Lebanese Coast, Eastern Mediterranean

“…The Lebanese coastal zone, which constitutes one part of the carbonate platform that covers most of the Eastern Mediterranean basin, is the geological result of the carbonated marine sedimentation between the Jurassic and the Quaternary periods (Abdel-Rahman and Nader 2002).…”

Lead and its isotopes in the sediment of three sites on the Lebanese coast: Identification of contamination sources and mobility

“…The Lebanese coastal zone, which constitutes a part of the carbonate platform that covers most of the Eastern Mediterranean basin, results geologically from the carbonate marine sedimentation between the Jurassic and the Quaternary periods (Abdel-Rahman and Nader, 2002). Geological surveys indicate the presence of a thick layer of dolomite, marls or chalk.…”

Ceramic patchwork in Hellenistic to Byzantine Phoenicia: regionalization and specialization of vessel production

“…These differences are easiest to establish in the case of deposits dated from the late Jurassic to the mid-Cretaceous, when many types of limestone, sandstone, loam and volcanic ash were formed (Walley n.d.: Fig. 5;Abdel-Rahman and Nader 2002). Basalt folds are the only kind of volcanic (igneous) rock identified in this region, located primarily on the southern and northern peripheries of Phoenicia.…”