Origin and timing of siderite cementation in Upper Ordovician glaciogenic sandstones from the Murzuq basin, SW Libya
2006 (English)In: Marine and Petroleum Geology, ISSN 0264-8172, Vol. 23, no 4, 459-471 p.Article in journal (Refereed) Published
The origin and timing of siderite cementation have been constrained in relation to depositional facies and sequence stratigraphy of Upper Ordovician glaciogenic sandstones from the Murzuq basin, SW Libya. Optical microscope, backscattered electron imagery, and carbon and oxygen stable isotope analysis have revealed that siderite is of eo- and mesogenetic origin. Eogenetic siderite is Mg-poor with a mean composition Of (Fe91.7Mg1.5Ca0.3Mn6.5)CO3, and occurs in paraglacial, tide-dominated deltaic highstand systems tract (HST) sandstones, in paraglacial, foreshore to shoreface HST sandstones and in postglacial, Gilbert-type deltaic lowstand systems tract (LST) sandstones. This siderite is typically of meteoric water origin that influxed into the LST and HST sandstones during relative sea level fall and basinward shift of the strandline.Mesogenetic siderite, which engulfs and thus postdates quartz overgrowths and illite, is Mg-rich with a mean composition of (Fe72.2Mg21.7Ca0.8Mn5.3)CO3 and occurs in the paraglacial, tide-dominated deltaic HST sandstones, in paraglacial foreshore to shoreface HST sandstones, in glacial, tide-dominated estuarine transgressive systems tract (TST) sandstones, in postglacial, Gilbert-type deltaic LST sandstones, and in postglacial, shoreface TST sandstones. delta O-18(V-PDB) values of this siderite, which range between -22.6 and -13.8 parts per thousand, suggest that precipitation has occurred from evolved formation waters with delta O-18 values between -14.0 and +1.0 parts per thousand and was either meteoric, mixed marine-meteoric and/or marine in origin by assuming postdating quartz overgrowths and illite temperature between 80 and 130 degrees C.
Place, publisher, year, edition, pages
2006. Vol. 23, no 4, 459-471 p.
siderite, glaciogenic sandstone diagenesis, sequence stratigraphy, depositional facies, Upper Ordovician, the Murzuq basin, SW Libya
Earth and Related Environmental Sciences
IdentifiersURN: urn:nbn:se:uu:diva-19754DOI: 10.1016/j.marpetgeo.2006.02.002ISI: 000239289400003OAI: oai:DiVA.org:uu-19754DiVA: diva2:47526