Carbonate Diagenesis in Non-Marine Foreland Sandstones at the Western Edge of the Alleghanian Overthrust Belt, Southern Appalachians

  1. Sadoon Morad
  1. K. L. Milliken

Published Online: 17 APR 2009

DOI: 10.1002/9781444304893.ch4

Carbonate Cementation in Sandstones: Distribution Patterns and Geochemical Evolution

Carbonate Cementation in Sandstones: Distribution Patterns and Geochemical Evolution

How to Cite

Milliken, K. L. (1998) Carbonate Diagenesis in Non-Marine Foreland Sandstones at the Western Edge of the Alleghanian Overthrust Belt, Southern Appalachians, in Carbonate Cementation in Sandstones: Distribution Patterns and Geochemical Evolution (ed S. Morad), Blackwell Publishing Ltd., Oxford, UK. doi: 10.1002/9781444304893.ch4

Author Information

  1. Department of Geological Sciences, University of Texas, Austin, TX 78712, USA

Publication History

  1. Published Online: 17 APR 2009
  2. Published Print: 29 MAY 1998

ISBN Information

Print ISBN: 9780632047772

Online ISBN: 9781444304893

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Keywords:

  • carbonate diagenesis in non-marine foreland sandstones, southern Appalachians;
  • Alleghanian overthrust belt;
  • petrography and geochemistry of carbonate components;
  • Ferroan dolomite and ankerite;
  • gravity-driven meteoric fluids

Summary

The late Palaeozoic synorogenic foreland sandstones of the southern Appalachian basin are relatively carbonate poor (average < 3 vol%) but locally contain siderite, calcite and ferroan dolomite/ankerite as cements and grain replacements. Petrographic evidence shows that siderite is an early precipitate, followed by a generation of Mg- and Fe-rich calcite (average Ca95.6Mg1.8Fe2.4Mn0.2CO3) that preceded quartz cementation. Ferroan dolomite/ankerite postdates quartz cementation and is followed in turn by a generation of relatively Mn-rich calcite (average Ca97.4Mg0.6Fe1.5Mn0.5CO3). Early calcite is highly localized at the outcrop scale, though pervasively distributed at the thin section scale, and preserves intergranular volumes (IGVs) (30–40%) characteristic of relatively early stages of compaction. Other carbonates are highly localized in their distribution in thin section. Siderite is localized on expanded detrital micas. Ferroan dolomite and late calcite have a strong spatial affiliation with partially dissolved silicate grains, and are found in sandstones with markedly reduced IGVs (< 20%).

Elemental and isotopic values for all the authigenic carbonates suggest that fluids responsible for carbonate precipitation were most likely 18O depleted, enriched in organic carbon, and contained Mg, Fe, Mn and, in some cases, Sr mobilized by the alteration of detrital components in the sandstones and associated mudrocks. 87Sr/86Sr values fall into a range outside that of marine Sr, supporting a prominent role of silicate-derived components in carbonate precipitation. Temporal variation in carbonate mineralogy and compositions probably reflects the changing character of elemental sources during burial. Early phases (siderite and early calcite) may reflect the reaction of highly unstable Fe- and Mn-oxyhydroxides and clay-adsorbed Mg. Ferroan dolomite and ankerite may represent Mg, Fe and Mn mobilized by subsurface alteration of detrital clays and their surface coatings at elevated temperatures. The late generation of calcite formed after the sources of Mg and Fe were depleted, though Mn remained relatively high. Manganese in late carbonates was possibly derived from relatively resistant and late-reacting heavy minerals such as garnet or, alternatively, from fluids derived from deeper in the basin.