A sporomorph ecogroup model for the Northwest European Jurassic - Lower Cretaceousi: concepts and framework

Abstract

Based on recent vegetation distribution and an integration of macropalaeobotanical and palynological information, a palaeocommunity model is explored that may permit detailed interpretations of quantitative sporomorph distribution patterns in the Jurassic and Early Cretaceous of NW-Europe in terms of changes in palaeoenvironment (sea-level, climate). The conceptual model is based on the recognition of Sporomorph Ecogroups (SEGs) that reflect broad co-existing plant communities, viz. upland, lowland, river, pioneer, coastal, and tidally-influenced SEGs. In successive palynological assemblages, shifts in the relative abundance of SEGs are thought to be indicators of sea-level changes. Climatic changes may be recognised through significant shifts within the quantitative composition of individual SEGs.

Early Cretaceous vegetation and climate change at high latitude: Palynological evidence from Isachsen Formation, Arctic Canada

“…We base our inferences on actualistic principles and assume that certain paleoenvironments supported taxa with broadly similar ecological preferences (Abbink et al, 2004).…”

“…Mosses usually grow in moist soils typical of humid environments, but can also tolerate periods of drought (Abbink et al, 2004). Bryophyte spores are likely derived from scattered parent plants growing in humid, lowland environments, probably associated with riparian zones alongside rivers and marshes.…”

“…Most extant lycopsids occur in humid tropical regions, but can also be found in temperate and even polar areas where they often grow in moist settings, such as lowland, river, or tidally-influenced environments. Some Triassic lycopods appear to have been facultative coastal halophytes and inhabited marine shoreline environments in delta systems (Retallack, 1975) Konijnenburg-van Cittert, 2002;Abbink et al, 2004;Dejax et al, 2007;Schrank, 2010).…”

“…Vitreisporites pallidus attains a mean relative abundance of <1% of the pollen and spore sum (Figure 7), indicating rare occurrences of parent plants that probably grew in deltaic flood plain to backswamp environments (van Konijnenburg-van Cittert, 1971;Abbink et al, 2004;Dejax et al, 2007;Stukins et al, 2013).…”

“…Inaperturopollenites (also rare) pollen is also considered to have affinities to this family (Balme, 1995). Extant Araucariaceae are well adapted to drought and frequently grow in near shore environments (Abbink et al 2004). In the Jurassic and Cretaceous, high proportions of Araucariacites pollen are indicative of warm climates with low seasonality (Reyre, 1980;Mohr , 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 1989) and fossil trees are often associated with near-coastal depositional environments in the geologic record (Harris, 1979;Barale and Flamand, 1982;Vakhrameev, 1991).…”