Previous studies have shown that the effect of concurrent nontemporal processing on time estimation may vary depending on the level of difficulty ofthe nontemporal task. This is commonly interpreted within the context of so-called distraction/interruption models of temporal processing, which propose that as concurrent task difficulty or complexity is increased, temporal processing receives less attention. We hypothesize that the effect of nontemporal processing does not depend on the level of difficulty as such, but rather on the extent to which the concurrent nontemporal task specifically involves processing in short-term memory. Four experiments were run in which the short-term memory requirements of concurrent tasks were systematically varied, although all of the tasks were of comparable levels of difficulty. In the first experiment, the effect of memory search on simultaneous temporal productions was proportional to the number of items to search. As with reaction time, produced intervals were shown to increase linearly with the number of items in the memorized set. In Experiment 2, a visual search involving some load on short-term memory interfered in the same way with time production, although to a lesser extent. The last two experiments showed that performing attention-demanding visual search tasks that did not involve short-term memory did not lengthen simultaneously produced time intervals. This suggests that interference of nontemporal processing on time processing may not be a matter of nonspecific general purpose attentional resources, but rather of concurrent shortterm-memory processing demands.Prospective timing occurs when one is required to estimate the duration of a temporal interval that is to be presented. In such a situation, it is often reported that estimated duration decreases as a result of increasing concurrent nontemporal processing demands. This is commonly interpreted within the context of so-called distraction/interruption models of temporal processing, which propose that as concurrent task difficulty or complexity is increased, temporal processing receives less attention (Block, 1990;Brown, 1985;Fortin & Rousseau, 1987;Fraisse, 1984;Hicks, Miller, & Kinsbourne, 1976;McClain, 1983; Rousseau, Fortin, & Kirouac, in press;Thomas & Cantor, 1978;Vroon, 1970). The reduction of attention to temporal processing is assumed to result in less temporal information and, consequently, to shorter perceived duration. In spite of the accumulation of evidence, the distraction models still remain quite informal, which led Block to state that "Terms like attention to time and temporal information processing are unacceptedly vague" (p. 22).We believe that two basic questions should be addressed for some progress to be achieved. First, temporal-

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The sedimentary–diagenetic structure stromatactis is widespread in Palaeozoic spiculitic carbonate mud mounds, but occurs only sporadically in Mesozoic sponge carbonate mud mounds. Comparative analysis of Palaeozoic and Mesozoic stromatactis limestones suggests that this variation results from the degree of siliceous sponge skeletal rigidity and the amount of internal sediment accumulation in the original cavity network. Partial to entire filling by internal sediment resulted in a continuum, from a small amount of internal sediment and large amount of cement (stromatactis, common in the Palaeozoic), to only internal sediments (aborted stromatactis, common in the Mesozoic). These observations match independent lines of evidence concerning the siliceous sponge evolution and sediment recycling (e.g. bioerosion) across the Palaeozoic to Mesozoic biotic revolution.

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Sea-level changes and synsedimentary tectonics affected the development of three potential hydrocarbon reservoir intervals in the Silurian-lowermost Devonian part of the Gasp6 Belt on the margin of Laurentia. A relative sea-level curve is based on sequence analysis of facies and distribution of benthic faunas. The succession recorded two major, low-order sedimentary cycles, each composed of a regressive-transgressive couplet and represented by shallowing-and deepening-upward sequences. The first shallowing episode (S0 covered the Rhuddanian-Sheinwoodian (Llandovery-early Wenlock) interval, whereas a rapid deepening episode (D1) followed during the Hometian (late Wenlock). A second shallowing episode ($2) started during the late Hometian, and ended in the late Ludfordian (late Ludlow) or earliest Pridolian, and was then followed by a latest Silurian-Early Devonian deepening episode (D2). Potential reservoir rock units developed mostly during sea-level lowstands or early transgressions in the Gasp6 Belt. Comparison of the Gasp6 relative sea-level curve with eustatic curves, proposed for the same time interval, indicates that the Gasp6 curve was significantly influenced by local synsedimentary tectonics.Salinic extensional tectonics, a predominantly Late Silurian-Early Devonian (Ludlovian-Pragian) event, resulted in block faulting and tilting along normal listric faults. Interaction between block faulting and eustatic sea-level fall at the end of the Ludlovian-early Pridolian exposed the highest parts of the blocks to subaerial erosion and diagenesis, and allowed reefs and reef complexes to settle at the margins of the blocks, or on erosional remnants. Salinic extensional tectonics may also have provided suitable pathways for hydrocarbon migration and charge at various times during the mid-Silurian to Early Devonian, particularly for hydrocarbons that may have been generated in the underlying Cambro-Ordovician shales. In the northeastern part of the Gasp6 Belt, which is the most promising area for hydrocarbon reservoirs in the Gasp6 Peninsula, block faulting and tilting have changed the fluid migration pattern from an updip-northeastward flow from the basin centre to basin margin during the Late Ordovician to early Late Silurian, to a potential updip-southwestward flow in each faulted block during the early Late Silurian. Basin tectonics may have played a significant role in driving hydrocarbon-rich fluids toward potential reservoirs, such as the Llandoverian ValBtillant sandstone bodies, the Sayabec carbonate sands and knob reefs, or the West Point reefs.li~surcn~ Les fluctuations du niveau matin et la tectonique synsrdimentaire ont influenc6 le d6veloppement de trois horizons susceptibles de constituer des rrservoirs prtrolif'eres dans le Silurien -tout drbut Drvonien de la Ceinture de Gasprsie la marge de Laurentia. Une courbe relative des niveaux matins a 6t6 construite ~t partir de l'analyse s6quentielle des facies et de la distribution des faunes benthiques. La succession a archiv6 deux grands cycles principau...

This contribution provides an overview of the geological setting, stratigraphy, tectono-sedimentary evolution, and paleogeography of the post-Taconian-pre-Carboniferous sequence of the Gasp6 Belt. The sequence has been shaped by two tectonic pulses: the Salinic disturbance that began during the Early Silurian (Telychian) and persisted until the Early Devonian (Pragian), and the ensuing Acadian Orogeny in the Early to Mid-Devonian (Emsian-Eifelian).The shelf and shelf-edge history at the Laurentian margin along the Qurbec Re-entrant-St. Lawrence Promontory can be summarized in five broad phases that resulted from the interplay of tectonics and sea-level change. Phase 1 is a Llandoverian-Wenlockian regressive phase (R~) related to post-Taconian successor basin infilling, which culminated in extensive carbonate platform development. Phase 2 is a late Wenlockian-Ludlovian transgressive phase (T~). Phase 3 corresponds to a later Ludlovian-Pridolian second regressive phase (R2). Phases 2 and 3 were accompanied by extension faulting, block tilting, and the development of reefs, reef complexes and reef tracts along the Gaspr-Trmiscouata shelf. Phase 4 is an Early Devonian phase of accelerated subsidence (transgression T2) affecting the northwestern part (Qurbec Re-entrant area), while the southeastern part (St-Lawrence Promontory area) was previously uplifted as a result of Laurentia colliding with the western margin of Gondwana-related terranes to the south. Phase 5 is the final regression (R3) related to the Acadian Orogeny. RI~SUMI~Cet article pr6sente une vue d'ensemble du contexte grologique, de la stratigraphie, de l'6volution tectono-s6di-mentaire et de la pal6ogrographie de la s6quence post-taconienne h prr-carboniff'ere de la Ceinture de Gasp6sie. I1 se veut un cadre auquel les articles de ce numrro sp6cial des bulletins de la Canadian Petroleum Geology pourront se rattacher. La srquence a 6t6 modelres par deux pulsations tectoniques: la pulsation salinique qui a commenc6 au Tdlychien (Silurien pr6coce) et qui s'est poursuivie jusqu'au Praguien (Drvonien prdcoce); et l'orog6nie acadienne qui a suivi et qui a agi de l'Emsien ~t l'Eifelien (Drvonien pr6coce et moyen). L'histoire du plateau marin et de sa marge, adjacents h Laurentia le long du rrentrant de Qurbec et du promontoire du Saint-Laurent, se rrsume selon cinq grandes phases rrsultant de l'interaction entre la tectonique et les fluctuations du niveau marin. La phase 1 correspond ~t une phase rrgressive (R1) au Llandovrrien-Wenlockien, relire au remplissage du bassin successeur post-taconien; elle a culmin6 avec le d6veloppement d'une plate-forme calcaire tr~s 6tendue. La phase 2 est une phase transgressive (T1) qui eut lieu h la fin du Wenlockien-Ludlovien, alors que la phase 3 correspond ~t une seconde rrgression (R2) h la fin du Ludlovien-Pridolien. Ces deux derni~res phases ont 6t6 accompagn6es d'une tectonique d'extension qui a dissrqu6 le plateau en blocs basculrs sur lesquels se sont implant6s et d6velopp6s J GIRGAB. Groupe interuniversitaire de Rec...