seamletn.

/ˈsiːmlɪt/Etymology: < seam n.1 + -let suffix.
the world > the earth > structure of the earth > structural features > thin layer > [noun] > separating strata
1891 J. C. Atkinson 395 The bed of laminated clay, with intercalated seamlets of very fine sand.
This entry has not yet been fully updated (first published 1911; most recently modified version published online March 2018).