Submarine cements; the peloidal question

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Authors:Macintyre, Ian G.
Author Affiliations:Primary:
Smithson. Inst., Natl. Mus. Nat. Hist., Washington, DC, United States
Volume Title:Carbonate cements
Volume Authors:Schneidermann, Nahum, editor; Harris, Paul M.
Source:Special Publication - Society of Economic Paleontologists and Mineralogists, Vol.36, p.109-116; Carbonate cements revisited ; a symposium sponsored by the Society of Economic Paleontologists and Mineralogists, Dallas, TX, Apr. 1983, edited by Nahum Schneidermann and Paul M. Harris. Publisher: SEPM (Society for Sedimentary Geology), Tulsa, OK, United States. ISSN: 0097-3270. ISBN: 0-918985-37-4
Publication Date:1985
Note:In English. 35 refs.; illus.
Summary:The origin of peloidal textures common to submarine substrates lithified by Mg-calcite has been a subject of controversy. A review of the proposed origins of this diagnostic feature of Mg-calcite submarine cements reveals four suggested sources for these peloids - algal, sediment, replacement and precipitate origins. A reconsideration of both the petrographic and chemical characteristics of these peloidal textures indicates that they probably originate primarily in chemical processes that may involve repeated nucleation around centres of growth. Several factors support this hypothesis: the peloids have a generally limited size range; their shape is typically spherical; the best-developed peloidal textures occur in restricted microcavities; peloidal textures exhibit well-developed zonation in many cement crusts; peloids and associated Mg-calcite rim cements have a similar chemical composition; and textural and depositional fabric characteristics are similar in Mg-calcite peloids and in precipitated spheroidal aggregates of pyrite. The pelletizing action of cryptic organisms and calcification of algal filaments also play a role. With the recognition that some calcite peloidal textures can be formed chemically, caution is urged in interpreting the origin of 'pelleted' limestones. [C.N.]
Subjects:Carbonate rocks; Cement; Cementation; Diagenesis; Genesis; Limestone; Marine environment; Sedimentary rocks; Sedimentation; Sediments; Submarine environment; Textures; Environment; Peloidal texture
Abstract Numbers:87M/1610
Record ID:1986041245
Copyright Information:GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data from Mineralogical Abstracts, United Kingdom, Twickenham, United Kingdom
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