Not all rhodoliths need a bed–depositional mechanisms in shallow water Sporolithon nodosum rhodoliths from the Whangaparaoa peninsula (North Island, New Zealand)

Teichert S, Mölg T, Pyko I, Kropac E, Marriott P, D'Archino R, Cullen N, Basso D, Persch N, Bach S, Lis E, Masters B, Nelson W (2026)

Publication Type: Journal article, Original article

Publication year: 2026

Journal

DOI: 10.1111/sed.70143

Open Access Link: https://onlinelibrary.wiley.com/doi/10.1111/sed.70143

Abstract

Rhodoliths, formed by crustose coralline algae (CCA), are prominent components
in carbonate platform deposits, contributing to the characteristic
rhodalgal facies. Their formation is influenced by both biological and
physical factors, and under specific conditions, they can accumulate,
forming extensive rhodolith beds. This study examines the depositional
mechanisms underlying the formation of monospecific (Sporolithon nodosum)
shallow-water rhodoliths from the Whangaparaoa Peninsula, North
Island, New Zealand. The findings suggest that these rhodoliths originate
in subtidal rocky channels at approximately 5 m depth, by the encrustation
of nuclei derived from surrounding geological strata. Following their
formation, these rhodoliths are transported into intertidal channel systems
and eventually deposited in supratidal beach areas. Notably, the structure,
morphology and composition of rhodoliths across these three depositional
settings exhibit minimal variation, suggesting that the rhodoliths belong
to a strongly interconnected coastal system with only brief intervals
between translocation events. In this context, the study provides a sedimentological
model for the development of rhodoliths in a coastal setting.
Furthermore, it challenges the presence of a significant rhodolith bed
sensu stricto in deeper offshore waters, as exploratory diving surveys
revealed extensive sand deposits that hinder rhodolith development in
these areas.

Authors with CRIS profile

Involved external institutions

University of Otago New Zealand (NZ)

How to cite

APA:

Teichert, S., Mölg, T., Pyko, I., Kropac, E., Marriott, P., D'Archino, R.,... Nelson, W. (2026). Not all rhodoliths need a bed–depositional mechanisms in shallow water Sporolithon nodosum rhodoliths from the Whangaparaoa peninsula (North Island, New Zealand). Sedimentology. https://doi.org/10.1111/sed.70143

MLA:

Teichert, Sebastian, et al. "Not all rhodoliths need a bed–depositional mechanisms in shallow water Sporolithon nodosum rhodoliths from the Whangaparaoa peninsula (North Island, New Zealand)." Sedimentology (2026).

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