Contributions to Modern and Ancient Tidal Sedimentology: an introduction to the volume

BERNADETTE TESSIER┼* and JEAN-YVES REYNAUD╬

┼ CNRS UMR 6143 M2C - University of Caen Normandie, 24 rue des Tilleuls, 14000, Caen, France

╬ University of Lille - CNRS, UMR 8187 LOG, Cité Scientifique, F 59 000, Lille, France

* Corresponding author: bernadette.tessier@unicaen.fr

HISTORY OF THE 'TIDALITES' CONFERENCE PROCEEDINGS

Besides pioneer works of the 60s, the tidal sedimentologist community really emerged in the 70s (see Klein, 1998). The first international conference on tidal sedimentology took place in 1973 in Florida (USA). It was devoted to carbonate facies, less to siliciclastic deposits and mostly to intertidal areas. The conference resulted in a book gathering case studies (Ginsburg, 1975). The fining-upward tidal flat sequence represented at this time the tidal facies model; and this was mainly applied to carbonates. The growing knowledge in siliciclastic tide-dominated environments was synthesized a few years later by Klein (1977). Following the paper of Visser (1980) demonstrating the record of tidal cycles in estuarine dunes, clastic tidal sedimentology evolved quickly towards more comprehensive and quantitative studies, both ancient and modern. A community was born.

In 1985, this community met in Utrecht (Netherlands) at the '1st Clastic Tidal Deposits symposium'. The proceeding book contains 31 papers, covering a large spectrum of topics, including facies and stratigraphic studies, from the offshore to the nearshore (de Boer et al., 1988). Few articles are devoted to processes and modelling but many focus on modern shelf tidal bodies description and surveying. As noted by Davis et al. (1998), the concept of tidal bundles is expressed for the first time in this book.

The 2nd conference, held in 1989 in Calgary (Canada), gave rise to another book of 26 papers (Smith et al., 1991). Beyond the increasing range of topics covered (e.g. the study of primary processes, such as flocculation), this book contains the pioneer paper by G. Allen establishing the estuarine tripartite facies and stratigraphic model of the Gironde estuary (SW France). The growing knowledge on modern tidal settings has been applied at the scale of petroleum reservoirs (e.g. Cretaceous Western Interior seaway).

The 3rd conference, named 'Tidal Clastics', took place in 1992 in Wilhelmshaven (Germany). The proceeding book (Flemming & Bartholomä, 1995) contains 23 papers, highlighting the increasing interest for studies dedicated to modern processes and facies in nearshore settings such as tidal inlets and tidal deltas. Wave and tide interactions are also considered. Ground penetrating radar appears as a new technique to explore ancient tidal subsurface outcrops.

In 1996, the 4th conference was held in Savannah (USA) and founded the 'Tidalites' name of the series. The proceeding book (Alexander et al., 1998) contains 17 papers and three thematic sessions; one on the Wadden Sea, a second one on tidal rhythmites and a third one on stratigraphy, with study cases of reconstructions of incised valley fills (in the Holocene and the rock record).

This conference was marked by a decrease in participation and correlatively a decrease in the number of papers published in the proceedings. This probably reflects the increase in the range of topics covered by the tidal sedimentologist community and, hence, the need to publish more continuously in international journals.

This change was confirmed as the next conference, Tidalites 2000, in Seoul (South Korea), brought only 12 papers, published in a special volume of the Korean Society of Oceanography (Park & Davis, 2001) and was mostly devoted to modern tidal settings in China, Korea and Japan.

The Tidalites 2004 conference was held in Copenhagen (Denmark) and 19 papers were published in a special issue of Marine Geology (Barholdy & Kvale, 2006). Most articles are dedicated to modern processes and especially on fine-grained sediment dynamics and budgets (turbidity maximum, flocculation, tidal marsh sedimentation). Only four papers deal with stratigraphy, one in the Holocene and three in the rock record.

The Tidalites 2008 conference took place in Qingdao (China) and no proceedings were published. During the conference, contributions were mostly focused on open coast tidal flats and tide-dominated deltas characteristic of Asian tidal seas, mud flats and salt marshes, as well as fluid muds in tidal channels. The conference was also marked by an increase of numerical and flume modelling of hydro-sedimentary dynamics and a rise of studies dedicated to climate and anthropogenic changes and coastal engineering.

To summarize, since the beginning, the Tidalites conference logically reflects the research made by the organiser teams rather than a general, worldwide evolution in tidal sedimentology. For instance, the North American conferences, in Calgary and Savannah, have highlighted facies and stratigraphic aspects, in relationship with a petroleum-oriented perspective, while the European meetings, in Wilhemshaven and Copenhagen, focused more on modern settings and processes. The Asian conferences, in Seoul and Qintao, put forward challenging environmental issues. At the same time, the Tidalites community has become more diverse and the pressure on young colleagues for publishing their research works in international journals has increased.

To get a more accurate idea of the tidal sedimentology production in the last years, we made a rapid overview of the articles published between 2009 and 2015 in international journals of the geosciences featuring the keywords tide or tidal in the title and sediment or deposit in the abstract. The query sent back about 400 papers mostly covering the following subjects:

• Facies and architecture in siliciclastics: IHS and fluvial-tidal transition. Tidal deltas and inlets. Wave-dominated, open-coast tidal flats. Tidal signature in open coastlines, muddy coastlines, shelves and slope systems. Carbonate peritidal flats and channels, offshore bioclastic carbonate bodies. Tidal straits.
• Biota: Benthic diatoms/foraminifera to assess tidal changes and long-term tidal flat dynamics. Ichnology of tidal environments. Tides and life: bacterial mats, Cambrian explosion.
• Processes and Modelling: Tidal bores, tidal channels and fluid muds. Tidal bars, ridges and inlets. Offshore dunes and shelf sand transport. Internal tides and deep sands, gas hydrates; tide influenced hyperpycnal flows and turbidites. Effect of sea-level rise on tidal range, estuarine circulation. Palaeotidal reconstructions.
• Climate: Effect of storms on tidal systems. Tide-storm interplay in the evolution of offshore dunes. Rapid, climate or sea-level changes and morphodynamic evolution of coastal marshes and freshwater wetlands. Astronomical cycles and tidal rhythmites.
• Environmental studies: Carbon sequestration and geochemical tracing of tidal transport. Pollution records in tidal flats. Anthropogenic effects in tidal environments.

As a consequence of the diversification of tidal sedimentology and increase of contributors, there has been a need for more synthetic productions. Martinius & Van den Berg (2011) opened the way with their atlas of estuarine facies, partly based on the extensive lacquer peel collection of the Utrecht University. Also, the 27th IAS Meeting of Sedimentology in Alghero (Italy) in 2009 had a special session on Tidal Sedimentology, which resulted in a special issue of Sedimentary Geology providing more syntheses and fewer case studies than in the previous edited volumes (Longhitano et al., 2012). During the same period, a special issue of the Bull. Soc. Géol. France was published on the incised-valleys around France (Chaumillon et al., 2010). 6 of the 10 contributions in this volume focus on the tide-dominated to tide-influenced estuaries located along the Atlantic and Channel coasts. Finally, the textbook Principles of Tidal Sedimentology (Davis & Dalrymple, 2012) is the first general book dedicated to tidal sedimentology since that of Klein (1977) on clastic tidal facies and Stride (1982) on offshore tidal sands. Most authors from the steering committee of the past Tidalites conferences (except carbonate specialists) authored the chapters of this book, which provides the state of the art on typical tidal environments, including a renewed perspective on carbonates and for the first time a specific insight on the deep sea and well-known ancient tidal basins.

OUTLINE OF THE PRESENT VOLUME

The Tidalites 2012 conference was held in Caen (France) and gathered together about 100 colleagues. In addition to the 70 talks and posters covering the main fields of tidal sedimentology, the meeting offered the opportunity to visit the following sites: (i) the Arcachon basin and Gironde estuary on the Atlantic coast (Chaumillon & Féniès, 2012); (ii) the wave-dominated Somme estuary, in the Eastern Channel area (Trentesaux et al., 2012); (iii) the Anjou Miocene tidal crags (André et al., 2012); (iv) the Bay of Mont-Saint-Michel in the Western Channel (Tessier et al., 2012). The four field trip guide-books are grouped together in a single volume (ASF, 2012).

The Caen Tidalite 2012 conference brought about 17 papers, gathered in the present volume. The book content has been...