Cryptospores and miospores, their distribution patterns in the Lower Old Red Sandstone of the Anglo-Welsh Basin, and the habitat of their parent plants
Titel:
Cryptospores and miospores, their distribution patterns in the Lower Old Red Sandstone of the Anglo-Welsh Basin, and the habitat of their parent plants
Auteur:
RICHARDSON, J.B.
Verschenen in:
Bulletin of geosciences
Paginering:
Jaargang 82 (2007) nr. 4 pagina's 355-364
Jaar:
2007
Inhoud:
Palynomorphs are abundant in some fine-grained rocks of the Lower Old Red Sandstone (Lower O.R.S.) of the Anglo- Welsh Basin. In this study the distribution and relative abundance of sporomorphs (cryptospores and miospores) have been examined from samples collected from the uppermost Raglan Marl and St. Maughan’s formations from Ammons Hill and Ross on Wye [Ross–Tewkesbury Spur Motorway (M. 50) Herefordshire in the south and from uppermost Red Downton Formation (Ledbury Formation) and Ditton Formation from the Clee Hills (Shropshire) in the north (a distance of over 100 km)]. The stratigraphical interval examined equates largely to the lower and middle parts of the Lochkovian Stage except in the Clee Hills where the uppermost part of the stage may be present. The Lower O.R.S. sequence in the Anglo-Welsh Basin shows progressive offlap with the migration of medial and proximal facies (fluvial environments) to overlie the distal facies (marine-influenced environments) in the south. Dispersed palynomorphs have been examined from sections from the distal margins of the floodplain in the south [Ammons Hill and Ross–Tewkesbury Spur Motorway (M. 50) Herefordshire Sections] to more proximal areas of the floodplain in the north (Clee Hills). The relative abundance of major groups of cryptospores and miospores varies stratigraphically in the M. 50 and Clee Hill Sections reflecting the southern migration of facies belts and, although influenced by water transport, sporomorph distribution data may be used with caution to interpret potential habitats of their parent plants. In some cases cryptospores were dominant in sporomorph assemblages from distal sediments, deposited in a marine-influenced coastal plain, and their parent plants may therefore have been halophytic. In contrast, in the more proximal (upstream) sediments, except for those from the higher parts of the Brown Clee Hill sequence, cryptospores with granulate to apiculate sculpture and miospores, especially those with apiculate sculpture, are dominant.
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