Mid-cretaceous greenhouse environments and floral ecosystems of the south polar region (75-80°s): the tupuangi formation, Chatham Islands, Zealandia

• Main Author: Mays, Chris
• Format: Thesis
• Language: unknown
• Published: 2017
• Subjects: ethesis-20120124-125833; Mid-Cretaceous; Biostratigraphy; Palaeoclimates; Geology; Taxonomy; Palaeobotany; 1959.1/534061; monash:81636; Polar Ecology; Global Greenhouse; Open access; thesis(doctorate); Palynology; 2011; Chatham Islands; Tectonostratigraphy; Byrd; Marie Byrd Land; New Zealand; West Antarctica; Antarc*; Antarctica
• Online Access: https://doi.org/10.4225/03/58901f401bf64; https://figshare.com/articles/thesis/Mid-cretaceous_greenhouse_environments_and_floral_ecosystems_of_the_south_polar_region_75-80_s_the_tupuangi_formation_Chatham_Islands_Zealandia/4597717

For analogues of global warming, the mid-Cretaceous is held up as both an archetype and a warning. Using a combination of theoretical models and geological evidence, a consensus is revealing that polar latitudes experience the greatest degree of warming during global greenhouse conditions. The Tupuangi Formation of the Chatham Islands, New Zealand, is the highest latitude (~ 75-80°S) floral assemblage ever discovered from the mid- Cretaceous; as such, the Chatham Islands provide an unprecedented perspective into the most extreme effects of global warming. This research has provided important climatic and evolutionary implications for the flora and fauna in both a regional (e.g. Zealandia, Australia and Antarctica) and global context. The Tupuangi Formation, and its fossil flora record, reveals a benign terrestrial polar environment amid the regional context of tectonic rifting, and a global context of extreme greenhouse conditions. Based on the timing of structural and sedimentological attributes of the Tupuangi Formation, the tectonic and palaeoenvironmental context of the region was established for the first time. It was concluded that these sediments were deposited in a terrestrial, failed-rift basin of Eastern Zealandia prior to the onset of seafloor spreading between Zealandia and Marie Byrd Land, West Antarctica. Without ongoing orogenesis in the region, a trend of fluvial aggradation and thermal subsidence followed this failed-rift event; this resulted in an upsequence transition from high to low fluvial flow-rate, with increasing prevalence of swamps, peats and paralic settings. This thesis includes a quantitative spore and pollen analysis to achieve comprehensive biostratigraphic correlations of the Tupuangi Formation and ecological interpretations of the mid-Cretaceous south polar region. As typical for terrestrial basins, the Tupuangi Formation features several age-old problems of spore and pollen biostratigraphy and ecological reconstructions, including preservation biases and the inclusion of older, ...