The traditional interpretation of Coccolithus pelagicus as a cold water proxy is examined based on its distribution patterns in the water column off the Portuguese coast (using data from eleven cruises) and in Holocene surface sediment samples and Quaternary cores from the same region. Coccolithus pelagicus is common in the Portuguese upwelling system, an area where surface waters are predominantly of subtropical origin. Although revealing an affinity for low temperature upwelled waters, the species was found in waters up to 18ЊC associated with riverine plume and shelf-break fronts. C. pelagicus seemed to consistently occupy a particular ecological niche, between other phytoplankton groups, related to moderate turbulence conditions combined with nutrient availability. From this behaviour, it is proposed that C. pelagicus can be used as a tracer of the periphery of areas of enhanced productivity. Coccolithus pelagicus preferences for fronts of moderate temperature and salinity gradients are tentatively used to explain particular features of its sedimentary record. The repeated increase of C. pelagicus in thanatocoenoses (surface sediment assemblages) close to three river mouths, on the Portuguese shelf, are interpreted as a positive response to the development of riverine plumes. On the other hand, inconsistencies in the correlation between sea surface cooler-glacial and warmerinterglacial isotope stages and the relative abundance pattern of C. pelagicus during the Late Quaternary, as registered in two Galicia Bank piston cores (42ЊN), are tentatively explained in terms of shifts in the extent of the outer limit of the local palaeoproductivity belt off the Iberian Peninsula.

No abstract

No abstract

No abstract

51Massive fossil shell accumulations require particular conditions to be formed and may 52 provide valuable insights into the sedimentary environments favouring such 53 concentrations. Shallow-water shell beds appear to be particularly rare on reefless 54 volcanic oceanic islands on account of narrow, steep and highly-energetic insular 55 shelves where the potential for preservation is limited. The occurrence of an exceptional 56 coquina (Pedra-que-pica) within the Miocene-Pliocene deposits of Santa Maria Island 57 (Azores), therefore provides a rare opportunity to understand the conditions that led to 58 the formation and preservation of a massive shell bed at mid-ocean insular setting. This 59 study provides a detailed analysis regarding a 10-11 m-thick bivalve-dominated fossil 60 assemblage exposed at Pedra-que-pica on Santa Maria Island in the Azores. Integration 61 of taphonomical, palaeoecological and sedimentological observations are used to 62 reconstruct the genesis of the coquina bed and related events, and to discuss why such 63 exceptional sedimentary bodies are so rare on shelves around reefless volcanic oceanic 64 islands. 65 The sequence at Pedra-que-pica demonstrates a complex succession of sedimentary 66 environments in response to the drowning of an existing coastline during a period of 67 rapid sea-level rise. The Pedra-que-pica shell bed incorporates storm-related materials 68 and possible debris falls that originated nearby in a shallow and highly productive 69 carbonate factory. Deposition took place below fair-weather wave base, at around 50 m 70 depth, as inferred from the overlying volcanic succession. The preservation of this 71 coquina was favoured by deposition on a platform laterally protected by a rocky spur, 72 combined with rapid burial by water-settled volcanic tuffs and subsequent volcanic 73 effusive sequences. The recent exhumation of the deposit is the result of island uplift 74 and subsequent erosion.75 4 76 77