Lingulide Response to Severe Storms Recorded in Middle Triassic Strata of Northeastern British Columbia

Abstract

The distribution and significance of lingulide brachiopods (Lingularia selwyni Whiteaves) and the trace fossil Lingulichnus in storm-generated, subtidal sandstone beds in the upper Toad and Liard formations of northeastern British Columbia is summarized. Storm-generated sandstone beds from two depositional environments (proximal offshore to offshore transition and lower shoreface) were analyzed. Lingulide material is present in only a small proportion of the storm-generated sandstone beds in the study interval. This distribution is interpreted to reflect the inherent patchiness of infaunal communities both in pre-and post-event communities. Middle Triassic lingulides, like their extant relatives, were capable of (1) surviving storm-induced burial by extending their burrows upward and reconnecting with the sediment-water interface; (2) surviving storm-induced exhumation and transport; and (3) reinhabiting the sediment and reestablishing themselves in new settings after relocation by storms. Depositional environment played a pivotal role in the likelihood that individual lingulides survived storm events. Lingulide faunas deposited in the proximal offshore to offshore transition experienced up to 15%-25% mortality during storm events with most storm survivors (90%-95%) able to reestablish themselves in feeding position at the sediment-water interface. Lingulide faunas deposited in lower shoreface settings experienced considerably higher mortality, with ,60%-75% of the animals dying prior to the end of the storm and a further ,45% surviving the storm events but failing to reestablish themselves at the sediment-water interface in life position. Escape burrowing and reburrowing following exhumation, entrainment, and transport are fundamental adaptations for infauna occupying such dynamic depositional settings as the subtidal littoral zone (neritic zone). This ability was likely integral in the long-term success of lingulides in Phanerozoic marine successions.

Deep-sea Ordovician lingulide brachiopods and their associated burrows suggest an early colonization of proximal turbidite systems

“…Both forms are commonly associated with burrows (see below). Shells are usually larger than the size range of lingulide trace fossils (see below), perhaps reflecting a taphonomic bias resulting in the preferential preservation of larger and more robust adult body fossils over relatively small fragile juvenile shells 31 .…”

“…At a later stage, the lingulide possibly migrated downwards to avoid being entrained and carried away by relatively high-energy currents, as modern lingulides can retract into their burrows if unfavorable environmental conditions occur 1 , 2 . The organism must have been unable to reposition its burrow close to the sediment–water interface and became buried, possibly due to high burial depths, which constitute an important parameter that determine organism survival rate 31 . Lingulides can escape burial of 10–30 cm of sediment in a few hours to a few days after deposition, probably using a combination of scissor, rotary sawing, sliding, and gaping motions with their valves 18 , 98 , 99 , yet survivorship might be reduced in some lingulides when buried deeper than 15 cm 100 .…”

A diverse gastropod fauna from the shallow marine carbonate platform of the Yangou section (south China) in the immediate aftermath of the Permian–Triassic mass extinction

“…Other researchers proposed the shallow marine habitable zone hypothesis stating that in areas affected by breaking waves or frequent storm episodes, the storm‐aerated water could have had sufficient oxygen levels to provide habitable zones for benthic organisms (Beatty, Zonneveld, & Henderson, 2008; Zonneveld & Greene, 2010). However, the abundant and diverse gastropod and ostracod fauna occur in the thin‐ to medium‐bedded dark marlstone at the Yangou section, showing no evidence for wave breaking or storm activity, and the microfacies analyses suggest the water energy significantly decreased from oolitic shoal to shallow lagoon across the P‐Tr boundary (Tian et al, 2014).…”

“…Other researchers proposed the shallow marine habitable zone hypothesis stating that in areas affected by breaking waves or frequent storm episodes, the storm-aerated water could have had sufficient oxygen levels to provide habitable zones for benthic organisms (Beatty, Zonneveld, & Henderson, 2008;Zonneveld & Greene, 2010).…”

Life mode of in situ Conularia in a Middle Devonian epibole

“…3). Thus, 20 of the 23 ‘ Lingula ’ found in place were oriented with their commissural plane perpendicular to bedding and with their anterior end facing upward (see Zonneveld and Greene 2010 for in situ lingulids). These specimens occurred at multiple levels extending from about 0.5 m above the lowest observed occurrence of Conularia to about 0.3 m below its highest occurrence.…”