Orbitally controlled cyclicity around the Cretaceous/Tertiary boundary, northern South Island, New Zealand

Abstract

Outcrop gamma ray measurements are used as a proxy for terrigenous clastic component in CretaceousPaleocene carbonate-chert successions in northern South Island, New Zealand, and show Milankovitch-scale periodicity above the Cretaceous/Tertiary (K/T) boundary.Higher baseline values of the gamma ray records from sections in the south compared to those in the north reflect increased terrigenous clay content associated with shallowing in paleobathymetry towards the south. In each northern section, the gamma ray baseline level increases across the K/T boundary, consistent with an increase in terrigenous clay in the early Paleocene; this might record increased erosion due to destruction or change of vegetation or a fall in relative sea level. Peak amplitudes in the gamma ray record are higher for the early Paleocene, perhaps recording more pronounced climatic variability after the K/ T boundary event, and consistent with a South Atlantic record. Cycle frequencies in the Late Cretaceous are not well constrained due to the sparseness of biostratigraphic events but could be consistent with eccentricity. Biostratigraphic age control in the Paleocene constrains cycle frequency to c. 120 000 yr and suggests the early Paleocene climate in the high latitude, southwest Pacific, was modulated by orbital eccentricity.

Paleoenvironmental changes across the Cretaceous/Tertiary boundary at Flaxbourne River and Woodside Creek, eastern Marlborough, New Zealand

“…An increase in amplitude across the boundary is also evident in the gamma-ray record for Woodside Creek (Field & Hollis 2003). The predominance of the silica-rich phase in each cycle further implies that mean climatic conditions were significantly cooler than in the Late Cretaceous.…”

“…4) for which there is no sedimentological evidence, such as laminated or thin-bedded intervals. As the only constraint on this disconformity is that it must be above the FO of A. mayaroensis, we arbitrarily place it at 4 m below the K/T boundary to coincide with small but significant changes in bed thickness and gamma-ray variation at Woodside Creek (Field & Hollis 2003), including a decrease in average bed thickness, a baseline increase in gamma, and intensification of gamma peaks. Because of the uncertainty surrounding this disconformity, the following discussion is mainly restricted to paleoenvironmental trends above -4 m in each section.…”

South Pacific evidence for the long-term climate impact of the Cretaceous/Paleogene boundary event

“…Over approximately the same time interval, high-amplitude eccentricity cycles in carbonate flux and grain size in Walvis Ridge ODP Site 1262 indicates orbital pacing of CCD depth (Kroon et al 2007); the inference being that each pulse of deepening is linked to CO2 drawdown and climatic cooling. Eccentricity cycles have also been reported in the lower Paleocene sequence in Marlborough (Field and Hollis, 2003) although the coeval interval in North Pacific ODP site is described as "strange interval"…”

Environmental change prior to the K–T boundary inferred from temporal variation in the morphology of cheilostome bryozoans

“…3G). Cyclical patterns through Upper Cretaceous sediments and fossils have been attributed to environmental variation resulting from orbital forcing, caused either by the 100 ka eccentric, 41 ka oblique, or~21 ka precessional periods of Milankovitch cycles (Herbert and Dhondt, 1990;Park and Oglesby, 1991;Cunha and Koutsoukos, 2001;Field and Hollis, 2003;Lauridsen and Surlyk, 2008), the latter being most frequently detected (MacLeod et al, 2001). However, cyclicity wasn't tested in this study and the lack of fine biostratigraphical resolution makes it difficult to translate stratigraphical into temporal periodicity and uncover the root cause.…”