Selective colonization after storm events in a delta environment: applied ichnology from the early Miocene of Taiwan

Abstract

The sedimentological and palaeoecological interpretation of early Miocene age shallow marine deposits from one of the most emblematic geological areas of Taiwan – Yehliu peninsula – is not easy to approach in detail, and several contrasting proposals can be found in the literature. The present ichnological study helps to corroborate a delta environment as the most likely palaeoenvironmental setting, and to recognize the different sub-environments and hydrodynamic processes involved. The distal delta front displays the greatest trace fossil diversity, assigned to the Cruziana ichnofacies, including Ophiomorpha, Phycosiphon, Planolites, Rosselia, Schaubcylindrichnus, Scolicia, Thalassinoides and vertical equilibrium adjustment structures. The delta front records predominantly vertical traces attributable to the Skolithos ichnofacies. Amalgamated shell beds (most likely related to storm events) show concentrations of broken bivalve shells. After storm a selective colonization is interpreted, firstly by bioerosive tracemakers during times of decreasing sedimentation rate, followed by a dominance of trophic generalists such as those producing Ophiomorpha during post-storm sedimentation.

Keywords:

• Ichnofacies
• Miocene
• mixed-influenced delta
• storm
• Taiwan

Acknowledgements

The paper benefited from comments and suggestions by both reviewers (Dr. Fürsich and Dr. Ayranci) and the Associate Editor (Dr. MacEachern).

Disclosure statement

No potential conflict of interest was reported by the authors.

Funding

This study was funded by project CGL2015-66835-P (Secretaría de Estado de I + D+I, Spain), Research Group RNM-178 (Junta de Andalucía) and Scientific Excellence Unit UCE-2016-05 (Universidad de Granada). The research of Olmo Miguez-Salas is funded through a pre-doctoral grant from Spain´s Ministerio de Educación, Cultura y Deporte and the 2018 SUMMER PROGRAM IN TAIWAN FOR SPANISH GRADUATE STUDENTS. Ludvig Löwemark acknowledges financial support from the Ministry of Science and Technology of Taiwan [MOST grant 106-2116-M-002-021].