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Crowded tubular tidalites in Miocene shelf sandstones of southern Iberia

Rodríguez-Tovar, Francisco J. and Mayoral, Eduardo and Santos, Ana and Dorador, Javier and Wetzel, Andreas. (2019) Crowded tubular tidalites in Miocene shelf sandstones of southern Iberia. Palaeogeography, palaeoclimatology, palaeoecology, 521. pp. 1-9.

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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 draughtfill 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.
Faculties and Departments:05 Faculty of Science > Departement Umweltwissenschaften > Geologie-Paläontologie > Sedimentology (Wetzel)
UniBasel Contributors:Wetzel, Andreas
Item Type:Article, refereed
Article Subtype:Research Article
Publisher:Elsevier
ISSN:0031-0182
Note:Publication type according to Uni Basel Research Database: Journal article
Language:English
Identification Number:
Last Modified:12 Jul 2019 15:49
Deposited On:15 May 2019 07:07

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