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Volcanically mediated plankton blooms in the Central Belt of the Southern Uplands, Scotland, during the Llandovery

Rigby, S and Davies, S.J (2000) 'Volcanically mediated plankton blooms in the Central Belt of the Southern Uplands, Scotland, during the Llandovery.' Transactions of the Royal Society of Edinburgh: Earth Sciences, 91 (3-4). pp. 457-470. ISSN 0263-5933

Abstract

At Thirlestane Score and at four other localities in the Southern Uplands, graptolites of the Llandovery gemmatus Zone occur in couplets of lithologies immediately above thin ‘high-U’ bentonites. Above the bentonites, abundant graptolites, especially siculae, and a straight-line survivorship trend implies high productivity coupled with environmentally mediated mortality: the population structure expected in the early part of a plankton bloom. In the overlying facies, fewer, larger individuals and a convex survivorship curve suggest reduced productivity and internally mediated mortality. This is consistent with the later stages of a bloom where resources were waning but the ecological structure of the system was better developed. It is likely that the introduction of trace-metals, Fe or Al, to the water column via volcanic ash increased primary productivity, suggesting that macronutrients were available in the Southern Uplands system, allowing a bloom to be stimulated by the addition of volcanic products. This process is observed in modern open oceanic systems and implies a temporal continuity of control on the plankton despite complete faunal turn-over since the Silurian. These interpretations are most consistent with an open ocean geotectonic setting for the region.

Item Type: Article
Divisions: Chancelry
Date Deposited: 07 Jan 2018 22:04
Last Modified: 07 Jan 2018 22:04
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