ONE WORM IN THREE SUBSTRATES, NEOICHNOLOGICAL ANALYSES OF U-SHAPE STRUCTURES IN THE GOLFO NUEVO BEACHES, PATAGONIA, ARGENTINA.

The environmental analysis of the sedimentary record use different tools to characterized not just the main physical parameters of a sedimentary systems, also the development of life on it. Neoichnology, is an actualistic view of how the organisms are connected with the place where they live, providing modern models and ideas that serve as analogous. Many of the (neo)ichnological literature is concentrated on the Northern Hemisphere, and it is little known what happens southern the tropics. The description of organisms that lives either in hard- and soft-grounds is strange, and its description can help to interpret the paleodiversity in the fossil record. At Chubut province (Patagonia), in the Golfo Nuevo lives a polychaete that inhabits at the same time rocky abrasion platforms and sandy intertidal sediments. The present short-note is intended to described this occurrence and discuss its importance to ichnology

Editorial

Dear LAJSBA readers, we want to stay in contact with you for the second time, in this case starting the 27th Volume and after two years as LAJSBA Editors. First of all, we would like to thank the support received by the broad sedimentological community in Argentina and Latin America, particularly to the affiliates of the Asociación Argentina de Sedimentología. The journal has experienced important advances in these two years which are our main focus on this communication. In our first Editorial, in Vol. 25.1, we put emphasis in some relevant topics to work for during this time. One of them was the possibility of incorporate the complete record of the AAS Revista (pre-LAJSBA) to SCOPUS. This finally was achieved by the end of 2019, and SCOPUS database included all the papers from AAS-Revista between 1996-2004. To do this, very important steps were done by members of the AAS board and previous editorial teams, so thanks to them! Another previously mentioned aspect was the incorporation of a Digital Object Identifier (DOI) for all the papers of the journal. This theme is on progress at this moment through Scielo Argentina, they will generate DOI’s for LAJSBA papers before 2020, after that we will continue the process. Apart from these two topics, may be the most important news for LAJSBA is the regularity of the volumes! After a 2018 with a record of papers submitted to the journal we could publish 4 full numbers in a year (25.1, 25.2, 26.1 and 26.2) which means that in December 2019 we publish on-line and on-time the Volume 26.2. In the same way, the present number (27.1) is fully available on-line in July 2020 on our final repository, Scielo Argentina.Special thanks are for Augusto Varela and José Cuitiño, guest editors of the two highly successful Special Volumes dedicated to the Austral Basin. We invite to our readers to propose new thematic volumes for LAJSBA. Nowadays the LAJSBA is an entirely online-only free-access journal, with a high level of scientific quality and design which is recognized for the Latin American Earth-science community. In terms of bibliographic indexes, LAJSBA is taken into account by SCOPUS, Scimago, Latindex, GeoRef, and SciELO. Considering the recent modification of SCOPUS’s CiteScore, LAJSBA maintain its status in the 3rd Quartile in the Scimago Journal Ranking in all the categories where it is included (Geology, Paleontology, and Stratigraphy). We strongly believed that LAJSBA is ready to jump to the next level, becoming more attractive for the international community. We will work to maintain the path marked by previous editorial teams for this journal. To conclude, we want to emphasize that the future of LAJSBA depends on all of us, readers, authors, reviewers, and editors. The journal needs the support of the Latin American sedimentological community, not just to maintain its importance in our region, but to cross our borders. A special message is for our readers; we are looking forward to receiving your contributions

Editorial

 Estimados lectores de LAJSBA, como saben, nuestra revista ha renovado su equipo editorial para el período 2018-2022. Como Editor (Sebastian Richiano) y Editores Asociados (Renata Netto y Fernando Gómez), queremos contactarnos con ustedes por primera vez, en este caso iniciando el Volumen 25. Nos gustaría agradecer a la Comisión Directiva de la Asociación Argentina de Sedimentología por confiar en nosotros para esta tarea tan importante y comprometida. La revista, desde su inicio en 2005 (en continuación de la AASRevista que se publicara desde 1994), ha ido mejorando progresivamente su calidad y su visibilidad dentro de la comunidad científica. Esto se debe principalmente al esfuerzo de los diferentes equipos editoriales y, en este sentido, nos gustaría agradecer al ex editor Ernesto Schwarz y a la ex editora asociada Diana Cuadrado por su importante labor durante los últimos 4 años

<b>Mollusk shells for AAR: Dating the Quaternary shorelines along the coastline of Camarones, Chubut Providence, Argentina</b>

Argentinean Quaternary beach ridges are rich in marine fossil shells. However, the deposits lack material commonly used for the age constraint of coastal deposits, e.g., sediments for luminescence analysis or coral for U/Th analysis. To date, numerical ages have been determined by electron spin resonance and U/Th analysis of shells of the marine mollusk Ameghinomya antiqua, applications for which there are concerns due to the uptake of uranium following organism death. The amino acid racemization (AAR) geochronology method analyzes the extent of protein degradation within shells and provides an estimate of the time elapsed since the cessation of protein formation, commonly equated with the death of the organism. The application of the AAR method to mollusk shells in geochronological studies of Quaternary marine and coastal deposits is well-established, providing relative ages to stratigraphic sequences in the form of D/L values. In this study, we use samples of Ameghinomya antiqua to assess its suitability for AAR analysis in six Pleistocene field sites along the coastline of Camarones’ locality in Chubut Province, Argentina. These field sites represent beach ridges with maximum elevations ranging from ~9 to ~30 m aHT. The D/L values indicate deposits from at least two interglacial periods, consistent with previously published results, i.e., MIS 5 and MIS 11, although some discrepancies are present. The AAR results also show mixed-age deposits, indicating reworking of older deposits into younger ones. Our initial results show that AAR analysis of A. antiqua is able to discern interglacial deposits of differing ages and can be used to assess and complement ESR and U/Th results.Video presented in the EBRAM-CLAMA Congress 2023</p