SYMMETRICAL RIPPLES
Symmetrical ripples are moderately common sedimentary
structures. In cross-section, when
viewed perpendicular to the crests of the ripples, symmetrical ripple marks are
more or less evenly shaped - they are symmetrical. Their presence in sedimentary rocks is
diagnostic of deposition in a shallow water environment with a two-directional,
back-and-forth (oscillatory) current.
Symmetrical ripples marks are common in ancient shallow-water sandstone
facies.
Symmetrical ripples (above & below) developed in biogenic, aragonitic
(CaCO3), sand-size sediments on shallow subtidal seafloor just
offshore from Sand Dollar Beach, northwestern San Salvador Island, eastern
Bahamas.
