D. Kneale et Ha. Viles, Beach cement: incipient CaCO3-cemented beachrock development in the upper intertidal zone, North Uist, Scotland, SEDIMENT GE, 132(3-4), 2000, pp. 165-170
Beachrock has only rarely been observed previously along high latitude coas
ts. On several beaches on North Uist, NW Scotland at over 57 degrees N ther
e is evidence of small-scale beach cementation. An area of beach cement at
the back of Traigh Ear, as well as unconsolidated sands from the beach and
the adjacent Traigh Hornais, have been studied using SEM, XRD and petrograp
hical thin sections to throw light on the nature and causes of cementation.
Unconsolidated sands from both beaches are similar in grain sizes, shape a
nd mineralogy, but Traigh Ear grains commonly possess abundant cover of hig
h Mg calcite. The beach cement on Traigh Ear exhibits low porosity, with ab
undant micritic and aragonitic cements, showing no evidence of vadose cemen
tation along with traces of microorganisms. These findings contrast with th
e vadose, low Mg calcite cements commonly reported from temperate zone beac
hrocks. (C) 2000 Elsevier Science B.V. All rights reserved.