Ichnology and geochemistry: an integrated approach to early marine diagenesis in the Arabian Gulf

• Author / Creator

  Brown, Drew

• Neoichnological studies in carbonate-dominated tropical latitudes are sparse. Moreso, the coupling of diagenetic research utilizing ichnology has been largely limited to ancient successions. This thesis combines geochemical analyses with modern ichnological observations to better understand the early marine formation of firmgrounds and hardgrounds in the Abu Dhabi coastal sabkha. First, characterization of infaunal behavior and animal spatial variability help determine study sites of interest within an intertidal zone (Al Qantur lagoon). There exists a relatively low complexity and diversity of burrowing morphologies in Abu Dhabi as attributed to heightened environmental stressors, such as salinity, heat, and subaerial exposure, as well as upward seepage of saline continental brines. Porewater analyses indicate a stabilization of salinity within burrows, suggesting the infauna irrigate their burrows to cope with increasing salinity. Crustacean burrows enhance solute advection in the lower intertidal zone by increasing substrate permeability, facilitating the penetration of seawaters to greater depths. Additionally, our research demonstrates that some examples of firmground and hardground features develop in the subsurface, which challenges traditional interpretations of hardground formation as cemented, exposed seafloors. Here, we present spatially-resolved geochemical analyses to better understand the underlying mechanisms promoting the formation, and resulting diagenetic processes, surrounding firmgrounds and hardgrounds in the Abu Dhabi coastal sabkha. Firmgrounds and hardgrounds both originate through early marine cementation, and microbial sediment cohesion. However, their compositions differ, with firmgrounds predominantly composed of peloids, and hardgrounds characterized by foraminifera and mollusc shells. Hardgrounds display dissolution textures, while firmgrounds remain less affected. Dissolution in Al Qantur lagoon is primarily driven by the advection of continental brines in the upper intertidal zone. Additionally, bioturbation plays a significant role in altering water and sediment chemistry, as crustacean activity spatially influences solute distributions, and prevents cementation. The formation of firmgrounds and hardgrounds depends on a complex hydrological regime that transports solutes via marine and groundwater sources.

• Subjects / Keywords

  • Diagenesis
  • Abu Dhabi
  • Arabian Gulf
  • Carbonate sedimentology
  • Ichnology
  • Hardgrounds

• Graduation date

  Spring 2024

• Type of Item

  Thesis

• Degree

  Master of Science

• DOI

  https://doi.org/10.7939/r3-19jf-3r64

• License

  This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.