Analysis of Mineral Segregation inEuzonus mucronataBurrow Structures: One Possible Method Used in the Construction of AncientMacaronichnus segregates

Abstract

Mineralogical segregation of sand grains distinguishes the trace fossil Macaronichnus segregatis, which is composed of a felsic burrow infill with a mafic-and mica-rich burrow mantle. This study focuses on determining the mechanism by which M. segregatis trace-makers segregated mineral grains during deposit feeding. A modern opheliid polychaete, Euzonus mucronata, from Pachena Bay, Vancouver Island (Canada), was examined to explain the activities of their ancient counterparts. Microscopic videotaping of deposit feeding allowed for collection of data on ingestion and excretion through visual grain counts of felsic, mafic, and shell components. Normalization of these grain counts to the composition of the host sediment illustrates preferential ingestion of felsic grains over mafic. Shell fragments were generally avoided and visually mantled the burrows, obscuring the paucity of mafic grains in burrow infills. The avoidance of shell fragments is potentially a function of the large grain size, angular shape, surface texture, and/or associated low nutritive value. The preferential ingestion of felsic grains is attributed to en masse feeding in felsic-rich locales identified through sediment probing. This form of mineral segregation likely reflects the specific nature of the sediment and worm population. Accordingly, en mass deposit feeding in selected felsic-rich localities is one possible mechanism used in the construction of Macaronichnus segregatis and M. segregatis-like structures.

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

“…; Dafoe et al . ; Seike ). Opheliids burrow through the sands using peristaltic contractions and selectively ingest the sediment with a proboscis to feed from microbes or meiofauna living on grain surfaces or between grains (Savrda & Uddin ).…”

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

“…and Travisia sp., produce structures similar to the ichnospecies Macaronichnus segregatis (e.g. Clifton & Thompson 1978;Saunders & Pemberton 1988;Pemberton et al 2001;Gingras et al 2002;Nara & Seike 2004;Seike 2007, Seike 2008, Seike 2009Dafoe et al 2008a,Dafoe et al 2008bSeike et al 2011). Opheliids are well known for specific substrate distribution patterns and being restricted to substrata with relatively narrow particle size ranges (Harris 1991;Maciolek & Blake 2006).…”

“…The presence of haemoglobin in the tissues of some of these polychaetes has been postulated as assisting in aerobic metabolism maintenance during low tide (Dangott & Terwilliger 1986;De Souza & Borzone 2007). Opheliids perform two primary behaviours, deposit feeding and locomotion, and subsist dominantly on an epigranular food resource (Faulchald & Jumars 1979;Harris 1991;Pemberton et al 2001;Dafoe et al 2008b;Seike 2008). Opheliids burrow through the sands using peristaltic contractions and selectively ingest the sediment with a proboscis to feed from microbes or meiofauna living on grain surfaces or between grains (Savrda & Uddin 2005).…”

Mineralogical composition of sediment determines the preference for smooth particles by caddisfly larvae during case construction

“…lugworms, bivalves, crustaceans, chironomids, mayfly or caddisfly larvae, and amoebae). These biological activities and accompanying mineral aggregation/segregation are important factors not only for the builder itself but also for the environment and the diagenesis of the surrounding sediment (Dafoe et al, 2008;Zorn et al, 2010). Consequently, they often actively concentrate particular mineral and/or rock types in their constructions (e.g., Fager, 1964;Gaino et al, 2002;Dafoe et al, 2008).…”