Pollen and spores in marine Cretaceous/Tertiary boundary sediments at mid‐Waipara River, North Canterbury, New Zealand

Abstract

Terrestrial pollen and spores in late Maastrichtian to early Paleocene marine strata at mid-Waipara, New Zealand, permit reconstruction of contemporary vegetation and paleoclimates. During the latest Cretaceous, spore-pollen assemblages reflect a temperate rainforest with a prominent podocarp and tree ferns component, angiosperm pollen being mainly represented by Nothofagus and Proteaceae. Disruption of the vegetation at the Cretaceous/Tertiary (K/T) boundary is recorded by an increase in fern spores, reduction in gymnosperm pollen, and temporary loss of angiosperm pollen both in mid Waipara and in the terrestrial sections of Moody Creek Mine and Compressor Creek. Following an interval of fern dominance, gymnosperms and later angiosperms return to the palynological record. The floral turnover at the K/T boundary is comparable to palynological records from North America and Japan, indicating that disruption of vegetation was global. Fern dominance is estimated to have lasted several thousands of years, based on foraminiferal biostratigraphy of immediate post-K/T boundary strata. This is orders of magnitude greater than seen in normal seral successions following deforestation. We suggest that the observed vegetation succession is due to a prolonged period of low ambient light levels, sufficient for photosynthesis but favouring plants already adapted to these levels (such as forest ground stratum), accompanied by a moderate temperature and moisture regime.

The Cretaceous/Tertiary boundary event in New Zealand: Profiling mass extinction

“…The terrestrial palynomorphs in the mid-Waipara and Moody Creek Mine sections record abrupt disappearance of mixed forest vegetation at the K/T boundary, followed by rapid expansion of opportunistic fern species (Vajda et al 2001;Vajda & Raine 2003). The similarity of these records to those reported from North America (Nichols & Fleming 1990) provides convincing evidence for global destruction of terrestrial vegetation, either by freezing conditions associated with a post-impact winter (Alvarez et al 1980), global wildfires (Wolbach et al 1988), or a combination of these (Pope 2002).…”

“…As preservation of radiolarians and sponge spicules is poor, it is likely that any diatoms present in the original sediments have been lost during diagenesis. The mid-Waipara and Moody Creek Mine sections have similar records of recovery in terrestrial plant communities (Vajda et al 2001;Vajda & Raine 2003). Initial colonising fern species are replaced by tree ferns within 0.2-0.3 m of the K/T boundary in both sections.…”

“…The terrestrial palynomorph record at mid Waipara (Vajda & Raine 2003) indicates that cool climatic conditions began within Foraminiferal Zone Pa and persisted into upper Radiolarian Zone RP3, that is, a duration equivalent to the inferred cool climate period in Marlborough.…”

“…All these sections contain the geochemical fingerprint of the K/T impact fallout layer, albeit somewhat disturbed in the mid-Waipara section (Vajda et al 2001;Hollis et al 2003a). Flaxbourne, mid-Waipara, and Moody Creek Mine sections also contain earliest Paleocene microfossil successions (Strong 2000;Vajda et al 2001;Vajda & Raine 2003) equivalent to the most complete marine and terrestrial K/T boundary records in the Northern Hemisphere (e.g., Smit & Romein 1985;Nichols & Fleming 1990;MacLeod & Keller 1991;Norris et al 1999). Although the fallout layer is preserved at Woodside Creek, foraminifera indicate that earliest Paleocene Zone P0 (i.e., 30 000 yr) is missing, possibly due to a hiatus within the boundary claystone (Hollis et al 2003a).…”

“…Occurrences of slumps, olistostromes, and crossbedding in uppermost Cretaceous strata atTora, southeastern Wairarapa, indicate that local tectonic activity and uplift occurred in some areas . Physiognomic analysis of leaf assemblages (Kennedy 2003) and general features of terrestrial palynomorph (Vajda & Raine 2003), planktic foraminiferal, and radiolarian assemblages (Hollis et al 2003b) indicate cool to mild temperate oceanic and climatic conditions, with moderately high precipitation, for latest Cretaceous (Haumurian) New Zealand. Weak cyclic variation in clay content in uppermost Cretaceous strata in Marlborough may reflect climatic cycles, possibly with Milankovitch-scale periodicity .…”