Distribution, Petrography and Geochemistry of Early Dolomite in Cyclic Shelf Facies, Yates Formation (Guadalupian), Capitan Reef Complex, USA
- Bruce Purser,
- Maurice Tucker,
- Donald Zenger
Published Online: 14 APR 2009
Copyright © 1994 The International Association of Sedimentologists
Dolomites: A Volume in Honour of Dolomieu
How to Cite
Mutti, M. and Simo, J. A. (2009) Distribution, Petrography and Geochemistry of Early Dolomite in Cyclic Shelf Facies, Yates Formation (Guadalupian), Capitan Reef Complex, USA, in Dolomites: A Volume in Honour of Dolomieu (eds B. Purser, M. Tucker and D. Zenger), Blackwell Publishing Ltd., Oxford, UK. doi: 10.1002/9781444304077.ch7
- Published Online: 14 APR 2009
- Published Print: 25 MAY 1994
Print ISBN: 9780632037872
Online ISBN: 9781444304077
- distribution, petrography and geochemistry of early dolomite - Yates Formation (Guadalupian), Capitan Reef Complex, USA;
- early diagenetic shelf dolomites within sequence-stratigraphic framework;
- Permian Capitan reef complex;
- Upper Yates depositional facies and cycles;
- dolomite distribution - Walnut Canyon and Rattlesnake Canyon;
- dolomite petrography;
- timing of dolomitization;
- dolomite geochemistry;
- early dolomitization and relative sea-level changes;
- dolomitization - during deposition and subaerial exposure of depositional cycle
This paper documents the geometry, distribution, petrography and geochemistry of early diagenetic shelf dolomites within a sequence-stratigraphic framework. The Guadalupian Yates Formation is composed of siliciclastic/carbonate cycles, deposited under subaerial to subtidal and shallow-marine conditions respectively, on a gently basinward-sloping shelf. Each cycle is composed of a lower transgressive siliciclastic and restricted carbonate facies, and an upper open-marine to restricted high-stand carbonate facies, capped by a subaerial exposure surface.
The shelf strata are now composed of dolomite, whereas the basinward equivalent rocks, the massive Capitan Reef and the foreslope facies are mostly limestone. The stratigraphic distribution of dolomite, the landward and basinward migration of the dolomite–limestone interface, and cross-cutting relationships document the occurrence of several early generations of dolomite in each of the Yates cycles. Dolomite clasts ripped from the underlying unit are incorporated together with undolomitized clasts at the base of the cycles. Dolomitization events occur in supra- and intertidal facies during the landward shift of facies belts in the transgressive portion of the cycle, whereas during the late high-stand and subaerial exposure at cycle tops, the dolomite–calcite interface is shifted basinward and dolomitization occurs indiscriminately in supra-, inter- and subtidal facies.
Two types of dolomite are recorded in these deposits. Fine-crystalline dolomite is the most common and replaced carbonate grains, aragonitic and Mg-calcite cements and carbonate mud. Oxygen isotope data (δ18O is enriched up to 5‰ with respect to Permian marine values) and major element concentrations are consistent with dolomitization from a marine fluid, modified by evaporation, in an oxidizing environment. Coarse-crystalline dolomite, precipitated as a primary dolomite cement in fenestral pores, has a limited areal distribution. Oxygen isotopes (δ18O = –1.3 ± 1.8 σ) are also consistent with precipitation from seawater, possibly at higher temperatures and salinities. Carbon isotopes (δ18C = 5.0 ± 0.6 σ) and trace element concentrations suggest precipitation during or above the zone of bacterial sulphate reduction.
Both dolomite types are interpreted to have formed in response to seawater flow through the shallow subsurface driven by tidal pumping, or by storm-recharge flooding and evaporative pumping, and by high evaporation rates on the supra- and intertidal areas. Dolomitization occurs during both deposition and subaerial exposure of each depositional cycle. Dolomitization of supra- and intertidal facies within one cycle occurred approximately during a period less than 100 000 years, whereas dolomitization of subtidal carbonates (and of marine cements) in association with the exposure at cycle tops may be related to a longer time duration (200 000 or 300 000 years).