Department of Geological Sciences, University of Texas, Austin, Texas 78712, U.S.A.
Ecology of a Late Silurian fauna of graptolites and associated organisms
Article first published online: 9 OCT 2007
Volume 10, Issue 4, pages 267–286, October 1977
How to Cite
WATKINS, R. and BERRY, W. B. N. (1977), Ecology of a Late Silurian fauna of graptolites and associated organisms. Lethaia, 10: 267–286. doi: 10.1111/j.1502-3931.1977.tb00622.x
- Issue published online: 9 OCT 2007
- Article first published online: 9 OCT 2007
- 4th March, 1977.
The Ludlow Series of Wales and the Welsh Borderland represents an ocean-bordering basin and shelf which received a shoaling sequence of sediments in the late Silurian. Graptolites grade from highest diversity and density in basin areas to lowest diversity and density on the nearshore shelf. By analogy with modern zooplankton, this distribution is attributed to differentiation of surface water masses over basin and shelf. During Ludlow time, the center of graptolite abundance shifted northward, indicating a restriction and seaward movement of the basin water mass. Small nektic cephalopods and phyllocarids parallel distribution trends of the graptolites, as does a fauna of small bivalves and brachiopods which may have lived on floating plants. The water mass model accounts for most distributional patterns of pelagic organisms in this local area, and has broader application to the distribution and evolution of graptolites.