Red Beds - Secondary Red Beds

Secondary Red Beds

Secondary red beds are characterized by irregular color zonation, often related to sub-unconformity weathering profiles. The color boundaries may cross-cut lithological contacts and show more intense reddening adjacent to unconformities. Johnson et al. (1997) have also showed how secondary reddening phases might be superimposed on earlier formed primary red beds in the Carboniferous of the southern North Sea. The general conditions leading to post-diagenetic alteration have been described by Mücke (1994). Important reactions include pyrite oxidation:

3O2 + 4FeS2→ Fe2O3 (hematite) + 8S E = -789 kJ/mol

and siderite oxidation:

O2 + 4FeCO3 → 2Fe2O3 (hematite) + 4CO2 E = –346 kJ/mol

Secondary red beds formed in this way are an excellent example of telodiagenesis. They are linked to the uplift, erosion and surface weathering of previously deposited sediments and require conditions similar to primary and diagenetic red beds for their formation.



Read more about this topic:  Red Beds

Famous quotes containing the words secondary, red and/or beds:

    “The prime purpose of being four is to enjoy being four—of secondary importance is to prepare for being five.”
    —Jim Trelease (20th century)

    “To-night the winds begin to rise
    And roar from yonder dropping day:
    The last red leaf is whirl’d away,
    The rooks are blown about the skies;

    The forest crack’d, the waters curl’d,
    The cattle huddled on the lea;”
    —Alfred Tennyson (1809–1892)

    “Alice opened the door and found that it led into a small passage, not much larger than a rat hole: she knelt down and looked along the passage into the lovliest garden you ever saw. How she longed to get out of that dark hall, and wander about among those beds of bright flowers and those cool fountains, but she could not even get her head through the doorway.”
    —Lewis Carroll [Charles Lutwidge Dodgson] (1832–1898)