Generation of Buried Transient Landscapes and Residual Depth Anomalies

• Main Author: Conway-Jones, Benedict
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: University of Cambridge 2022
• Subjects: Iceland Plume; Dynamic Topography; Paleoclimatology; Faroe-Shetland Basin; Iceland; North Atlantic
• Online Access: https://www.repository.cam.ac.uk/handle/1810/342315; https://doi.org/10.17863/CAM.89737

During Cenozoic times, the Icelandic plume has played a dominant role in controlling periodic uplift of oceanographic gateways across the North Atlantic Ocean. Five exquisitely preserved Paleogene buried landscapes are mapped on three-dimensional seismic reflection surveys from the Faroe-Shetland basin. A regional biostratigraphic and lithostratigraphic framework shows that these transient landscapes recur at intervals of 2–4 million years. Dendritic drainage patterns recovered from these landscapes are disequilibrated and contain multiple knickzones and knickpoints that are systematically arranged within catchment areas. Applying the stream power law, longitudinal river profiles are inverted to calculate spatially and temporally varying uplift histories. These unique landscapes are attributed to laterally advecting pulses of hot material that travel away from the centre of the Icelandic plume. Kinematic modelling suggests that these pulses are 100±50 °C hotter than ambient plume material. There is a temporal relationship between timings of landscape exposure and transient volcanic activity. Globally, these landscapes are coeval with short-lived climatic hyperthermal events. A causal relationship is proposed, whereby pulses of basaltic volcanism serve as both sources of CO2 and triggers for methane release, thus generating hyperthermal aberrations. The present-day surface expression of the Icelandic plume is evaluated using a comprehensive database of residual depth measurements. This database suggests that the Icelandic plume head has a radius of ∼1500 km and a complex planform, consistent with free-air gravity and earthquake tomographic models. These observations cannot be reconciled with previous models of asthenospheric flow and lead to revised estimates of plume flux. An exhaustive database of residual depth measurements throughout the Atlantic Ocean is also presented. In particular, newly acquired seismic reflection surveys along the west coast of Africa reveal that dynamic topography varies spatially on ...