Contents lists available at ScienceDirect Palaeogeography, Palaeoclimatology, Palaeoecology journal homepage: www.elsevier.com/locate/palaeo Crowded tubular tidalites in Miocene shelf sandstones of southern Iberia Francisco J. Rodríguez-Tovar a, ⁎ , Eduardo Mayoral b,c , Ana Santos c , Javier Dorador d , Andreas Wetzel e a Departamento de Estratigrafía y Paleontología, Universidad de Granada, 18071 Granada, Spain b Departamento de Ciencias de la Tierra, Facultad de Ciencias Experimentales, Campus de El Carmen, Universidad de Huelva, Avda. 3 de Marzo, s/n, 21071 Huelva, Spain c CCTH - Centro de Investigación Científico Tecnológico, Universidad de Huelva, Avda. 3 de Marzo, s/n, 21071 Huelva, Spain d Department of Earth Sciences, Royal Holloway Univ. London, Egham, Surrey TW20 0EX, UK e Department of Environmental Sciences – Geology, University of Basel, Bernoullistrasse 32, CH-4056 Basel, Switzerland ARTICLE INFO Keywords: Thalassinoides Gyrolithes Tidal processes Neap-spring cycles Lunar fortnightly regime Miocene Algarve (Portugal) ABSTRACT The passive and active fill of burrows potentially stores information about sedimentary processes that are otherwise not preserved in the rock record. In recent years, abandoned passively-filled vertical burrows were introduced as “tubular tidalites” when their infilling displays rhythmic lamination reflecting a tidal signature. In the shallow-marine Miocene sandstones exposed at Oura (southern Portugal), 36 tubular tidalites occur in a 1.5 m-thick interval. Their high abundance is likely a consequence of both an environment favourable for the production of open burrows in a tidal setting, and post-depositional conditions facilitating the preservation of the tubular tidalites. Besides vertical tubes, 13 horizontal burrows preserve a tidal signature indicating draught- fill processes. All specimens belong to Thalassinoides and, for the first time, to Gyrolithes. The rhythmic infill of two well-preserved specimens shows two significant features: (1) The thickness pattern allows for differentiation into groups having 7 couplets (consisting of a dark and a light lamina) or multiples thereof, and (2) the thickness patterns of both, consecutive couplets as well as dark and light laminae match sine curves. Both patterns indicate a diurnal tidal cyclicity. The tidalites record up to four spring-tide and three neap-tide cycles. In addition to the neap-spring cycles, a long-period lunar fortnightly tide regime can be envisaged. The tubular tidalites imply diurnal tides during the Miocene in contrast to the Recent semidiurnal tides affecting southern Portugal. 1. Introduction Over the last decades, ichnology has become a useful approach in Earth Sciences to obtain supplementary information about environ- mental processes and factors, since burrowing organisms sensitively respond to the ecologic conditions in their habitat (Buatois and Mángano, 2011, and references therein). The behavior of tracemakers is documented by the biogenic sedimentary structures produced, which provide valuable information about the depositional setting (Pemberton et al., 2001; Taylor et al., 2003; MacEachern et al., 2007; Knaust and Bromley, 2012). Ichnology is, however, not restricted to the environ- ment-related ethological aspects of trace fossils; particular actively and passively filled burrows may store a sedimentary record that is other- wise not preserved (e.g., Wetzel, 2015). Of special interest are burrows infilled by material subsequently eroded from the sediment surface, but not from the burrows. Hence burrow fill can represent the only lasting record of a material. Three terms have become established in recent years to denote different processes: “tubular tempestites”, “tubular tidalites” and “tubular turbidites”. The term “tubular tempestites” was introduced first and refers to “forced fillings of subsurface burrows during storms” (Wanless et al., 1988). The deep-encased tubular tempestites have a high preservation potential, whereas that of the tempestite layers on the surface is lower. Tubular tempestites form in a stable, stiff or firm substrate, while open, mostly abandoned tubes are subsequently filled with sediment transported by storm-generated currents. Observations on modern open Callianassa burrows form the basis for this concept, but it has also been successfully applied to ancient sediments wherein large, open Callianassa-like burrows such as Ophiomorpha and Thalassinoides occur (Wanless et al., 1988; Tedesco and Wanless, 1991). Tubular tempestites were described, for instance, from Lower Cambrian sand- stones (Jensen, 1997), Cambrian-Ordovician deposits housing Tricho- phycus-related tubular tempestites (Droser et al., 2004), Permian silt- stones of the Skolithos-Cruziana ichnofacies containing Diplocraterion and Rhizocorallium filled with tempestite material (Bann et al., 2004), and Lower and Middle Jurassic mud-firmgrounds exhibiting https://doi.org/10.1016/j.palaeo.2019.02.012 Received 1 December 2018; Received in revised form 1 February 2019; Accepted 16 February 2019 ⁎ Corresponding author. E-mail address: fjrtovar@ugr.es (F.J. Rodríguez-Tovar). Palaeogeography, Palaeoclimatology, Palaeoecology 521 (2019) 1–9 Available online 19 February 2019 0031-0182/ © 2019 Elsevier B.V. All rights reserved. T