On the Origin and Age of the Arıburnu Beachrock, Gelibolu Peninsula, Turkey

• Published in: Turkish journal of earth sciences 2008-01, Vol.17 (4), p.803-819
• Main Authors: ERGİNAL, AHMET EVREN, KIYAK, NAFİYE GÜNEÇ, BOZCU, MUSTAFA
• Format: Article
• Language: English
• Subjects: Beachrock; beachrock, carbonate cement, intertidal lithification, diagenesis, Gelibolu Peninsula, Turkey; carbonate rock; cementation[sedimentology]; chemical composition; diagenesis; Diyajenez; Gelibolu Peninsula; Gelibolu Yarımadası; Geochemical analysis; Geochemistry; Geology; ICP-AES[analiz]; ICP-AES[analysis]; Jeokimya; Jeokimyasal analiz; Jeoloji; Karbonatlı kayaçlar; Kimyasal bileşim; lithification; OSL dating; OSL yöntemi ile yaş tayini; Petrografik özellikler; Petrographic characteristics; SEM analysis; Taşlaşma; TEM analizi; Yalıtaşı; Çimentolanma(sedimentoloji)
• ISSN: 1303-619X; 1300-0985; 1303-619X

The beachrock formation on the Arıburnu coast situated in the Gelibolu Peninsula has been studied by field observation, thin-section interpretation, physicochemical analyses including ICP-AES and SEM/EDS, and OSL dating. These analyses reveal the presence of different amounts of major (Si, Ca, Mg, K, Fe, Al and Na) and trace elements within the beachrock cement with Si (36.2%) and Ca (32.68%) dominating the overall composition. Beachrocks composed of highly-fractured and friable beds reach a total thickness of 80 cm extending from +60 cm at the uppermost level down to -1 m at their most seaward extent and grade from conglomerate to lithic arkose in vertical section. The total amount of CaCO3 ranges between 59.08% and 36% and the cement consists of high-Mg calcite based on EDS analysis. From SEM examination, four main morphologies were identified in cement material: (1) micritic coatings, (2) cryptocrystalline pore-filling cement, (3) meniscus cement and (4) microbial cement and suggest the presence of marine phreatic conditions with the exception of meniscus bridges, which imply that cementation may have been dominated by carbonate-rich meteoric waters at any successive stage of cementation. Five buried beachrock samples under unconsolidated beach sand were sampled for Optically Stimulated Luminescence (OSL) dating and show that the minimum and maximum ages of beachrock are 1.42±0.20 ka and 2.28±0.28 ka BP, respectively.