Subaerial meteoric calcitization and lithification of high-magnesian calcite muds, Belize

Conference · Fri Mar 01 00:00:00 EST 1991 · AAPG Bulletin (American Association of Petroleum Geologists); (United States)

OSTI ID:7159007

Mazzullo, S J; Bischoff, W D ^[1]

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1. Wichita State Univ., KS (United States)

Holocene ({lt}1000-1500 yrs old) high-magnesian calcite-dominated muddy sediments (1 m thick) on subaerially exposed cays in northern Belize are in the process of being converted to low-magnesian calcite micrite. Mineralogic stabilization and attendant lithification result from interaction of the sediments with meteoric fluids believed to be derived from seasonal upward discharge through subjacent Pleistocene limestones. The initial marine-derived sediments, composed of {gt}85% HMC (and minor skeletal aragonite), consist of mud and associated soritid and miliolid foraminifera both with MgCO{sub 3} content of 11-15 mol%, and isotopic compositions of -1.0 to -2.5{per thousand} PDB (O), 0 to +1.5{per thousand} PDB (C). With depth, lithified LMC crusts appear in the section, and the Mg concentration of the sediments and associated crusts decreases rapidly to 3 mol% or less, with a corresponding isotopic depletion to values approaching -7.0{per thousand} (O) and -5.8{per thousand} (C). Concomitantly there is progressive dissolution of skeletal aragonite in the sediments, reduction of porosity due to cementation by LMC, and in the muds, a decrease in Sr and increase in Mn contents. The resultant petrofabric of these lithified LMC deposits, derived from the alteration of HMC-dominated muds, is characterized by micrite with patches of pore-filling micritic and microsparitic LMC cements. Such a fabric is similar to and can be confused easily with calcitized aragonite-dominated precursor muds, except for the relative rarity in the samples examined of aragonite relicts in component microspar and/or pseudospar.

• OSTI ID: 7159007
• Report Number(s): CONF-910403-; CODEN: AABUD
• Journal Information: AAPG Bulletin (American Association of Petroleum Geologists); (United States), Vol. 75:3; Conference: Annual meeting of the American Association of Petroleum Geologists (AAPG), Dallas, TX (United States), 7-10 Apr 1991; ISSN 0149-1423
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
BELIZE
GEOLOGIC DEPOSITS
LIMESTONE
DIAGENESIS
MINERALIZATION
ARAGONITE
CALCITE
DISSOLUTION
DOLOMITE
MAGNESIUM
METEORIC WATER
QUATERNARY PERIOD
SEDIMENTS
SOLUBILITY
ALKALINE EARTH METALS
CARBONATE MINERALS
CARBONATE ROCKS
CENOZOIC ERA
CENTRAL AMERICA
ELEMENTS
GEOLOGIC AGES
GROUND WATER
HYDROGEN COMPOUNDS
LATIN AMERICA
METALS
MINERALS
OXYGEN COMPOUNDS
ROCKS
SEDIMENTARY ROCKS
WATER
580000* - Geosciences