[
    {
        "id": "authors:srjbx-fdc92",
        "collection": "authors",
        "collection_id": "srjbx-fdc92",
        "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20130605-074536811",
        "type": "article",
        "title": "Remarkably uniform bulk silicate \u03b4^(18)O values of terrigenous sedimentary rocks from the Central Appalachian and Ouachita geosynclines",
        "author": [
            {
                "family_name": "Burt",
                "given_name": "Emelia A.",
                "clpid": "Burt-E-A"
            },
            {
                "family_name": "Taylor",
                "given_name": "Hugh P., Jr.",
                "clpid": "Taylor-H-P-Jr"
            }
        ],
        "abstract": "The whole-rock \u03b4^(18)O values of terrigenous sedimentary rocks in the Appalachian Mountains are\nsurprisingly uniform, irrespective of mineralogy, age, lithology, environment of deposition, or\ngrain size. The bulk silicate (i.e. non-carbonate) portions of 75 Paleozoic shales, siltstones, and\nsandstones covering an age span from Ordovician to Permian range in \u03b4^(18)O only from +13.2 to +17.6, with a mean \u03b4^(18)O of +14.9. Non-marine samples have slightly lower mean \u03b4^(18)O (+14.7)\nand are isotopically somewhat more uniform than marine samples (+15.3). In spite of the overall\nhomogeneity, a systematic decrease in bulk silicate \u03b4^(18)O is observed in shales and siltstones going\nfrom the SW (Kentucky, Tennessee) to the NE (central Pennsylvania). This geographic trend in\n\u03b4^(18)O correlates with conodont color alteration index (CAl, a measure of organic metamorphism)\nbut not with age, depositional environment, or source region, and there is no correlation of bulk\nsilicate \u03b4^(18)O with conodont CAl for the sandstones. These systematics are interpreted to be the\nresult of oxygen isotope alteration during diagenesis; exchange with diagenetic pore fluids lowered\nthe bulk silicate \u03b4^(18)O of siltstones and shales by as much as 2.5 to 4.2 per mil, bringing these\nfiner-grained rocks closer to the \u03b4^(18)O values of the sandstones. These diagenetic changes partly\naccount for the overall oxygen isotopic homogeneity of the Ctntral Appalachian geosynclinal rocks\n(together with the thorough, grand-scale mixing of terrigenous sediment that occurred in the\nAppalachian geosyncline over several cycles of sedimentation, uplift, erosion, and reworking of\nsediments extending over hundreds of millions of years during the Paleozoic era). An analogous\nstudy of 14 terrigenous sedimentary rocks from the Ouachita Mountains (Oklahoma, Arkansas)\nshows a similar range of \u03b4^(18)O (+13.4 to +16.9, mean = +15.3), but suggests greater inherent\noxygen isotopic heterogeneity of source areas compared with the Central Appalachians. This\ncomplicates analysis of variation in bulk silicate \u03b4^(18)O due to diagenesis. However, a significant\ncorrelation (r = 0.95) is found between vitrinite reflectance (another measure of organic\nmetamorphism) and the difference in bulk silicate \u03b4^(18)O between interbedded shale and sandstone\npairs. Thus, because of their finer grain size, the bulk silicate \u03b4^(18)O values of the shales were\nshifted downward more than those of the sandstones during diagenesis.",
        "issn": "0016-7592",
        "publisher": "Geological Society of America",
        "publication": "Abstracts with Programs - Geological Society of America",
        "publication_date": "1993-10",
        "series_number": "6",
        "volume": "25",
        "issue": "6",
        "pages": "203-204"
    }
]