DeterminingEuzonus mucronataBurrowing Rates with Application to AncientMacaronichnus segregatisTrace-makers

Abstract

Assessing the temporal significance of invertebrate ichnofossils is essential in interpreting ancient organism behaviors, depositional settings, and bioturbation and sedimentation rates. The trace fossil, Macaronichnus segregatis, is known to represent the work of deposit-feeding polychaetes and commonly occurs as a pervasive structure in shallow-marine sandstone deposits. This study uses the polychaete Euzonus mucronata, which produces M. segregatis-like structures, as a modern analogue to the trace-making counterparts. Field measurements from Pachena Beach, Vancouver Island, Canada, included assessment of population densities and worm behaviors. Volumetric burrowing rates were obtained from a thinwalled aquarium constructed in the laboratory. The burrowing rate calculated for 5 Euzonus (0.089 cm 3 /hr) was extrapolated to populations (approximately 1,400-5,000 worms/m 2 ) estimated from Pachena Beach, which require 70-300 days to completely rework 0.1 m 3 of sediment. Calculated rates are dependent upon the limitations of simulating a natural setting in an aquarium, the population density assessment, and the particular characteristics of the worm population and foreshore at Pachena Bay. However, these initial estimates can still be applied to rock record examples such as the Macaronichnus segregatis found in the Appaloosa Sandstone of Alberta, Canada. In this unit, ancient worms persisted in dense populations and reworked sediment at a rate that exceeded deposition during overall foreshore aggradation.

Environmental variability of Macaronichnus ichnofabrics in Eocene tidal-embayment deposits of southern Patagonia, Argentina

“…Factors, such as geomorphology, sediment dynamics and nutrient distribution, may be highly variable and control the overall distribution of this trace fossil within a depositional environment (Dafoe et al . ,Dafoe et al. ; Seike , Seike ).…”

“…The primary controls on infaunal movement in the sediment appear to be fluctuations in hydraulic energy, oxygen content, sedimentation rate and nutrient content (Harris ; Dafoe et al . ; Seike , ).…”

“…; Misaka & Sato ; Maciolek & Blake ; De Souza & Borzone ; Seike , , ; Dafoe et al . ,b; Rowe ; Seike et al . ).…”

The significance of deep-water cryptic bioturbation in slope-channel massive sand deposits of the lower Rio Dell Formation, Eel River basin, California

“…As such, cryptic bioturbation can occur in clay through sand grain sizes and cryptobioturbation is largely limited to sand (Blanpied and Bellaiche, 1981;Dashtgard and Gingras, 2003;Dashtgard et al, 2008). Both types of "biodeformational fabrics" can be produced in a matter of days to weeks (Bromley, 1996;Dafoe et al, 2008a;Dashtgard and Gingras, 2003;Gingras et al, 2008;Taylor et al, 2003;Thayer, 1983).…”

Biology of shallow marine ichnology: a modern perspective

“…Another means of determining trace morphology is to place burrowing animals in aquaria and study the resultant burrow morphologies (e.g. Dafoe et al 2008). Aquaria have also been used in situ in sedimentary studies and removed after a time for laboratory analysis (Dashtgard & Gingras 2005b).…”