Sprecher
Beschreibung
The Horseshoe Canyon Formation of southern Alberta, Canada, preserves abundant plant fossils from the upper Campanian to lower Maastrichtian, but its macroflora is taxonomically outdated and underutilised for palaeoclimatic reconstruction. We documented fifty-eight plant taxa from the Morrin Bridge locality in the lower Maastrichtian Horsethief Member. The assemblage comprises diverse gymnosperms, particularly Cupressaceae, alongside cycadophytes and ginkgophytes, rare ferns, and diverse angiosperms, including Platanaceae, Cercidiphyllaceae, Trochodendraceae, Betulaceae, multiple indeterminate dicots, and two monocots. Leaf physiognomic palaeoclimate analyses and closest climatic analogue comparisons reveal a temperate oceanic to warm-summer humid continental climate. Net primary productivity estimates are consistent with a temperate seasonal forest or woodland/shrubland biome. Collectively, these results indicate a warm-temperate, humid, frost-free climate characterised by moderate thermal seasonality and limited precipitation seasonality, consistent with conifer-dominated temperate floodplain forests with a diverse angiosperm component. The climatic reconstructions align with palaeosol and sedimentological evidence for saturated floodplain environments transitioning toward thicker and more frequent palaeochannels, suggesting increasingly active fluvial conditions and an intensified hydrological regime relative to earlier deposits of the Horsethief Member. This assemblage provides an important baseline for refining regional palaeoecological reconstructions of Late Cretaceous vegetation in Alberta in the lead-up to the K–Pg extinction and offers environmental insight into dinosaur palaeoecology within the Horseshoe Canyon ecosystem.