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Geologica Acta: an International Earth Science Journal ISSN: 1695-6133 [email protected] Universitat De Barcelona España

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Geologica Acta: an International Earth Science Journal ISSN: 1695-6133 Geologica-Acta@Ija.Csic.Es Universitat De Barcelona España Geologica Acta: an international earth science journal ISSN: 1695-6133 [email protected] Universitat de Barcelona España Aceñolaza, G. Reply Geologica Acta: an international earth science journal, vol. 3, núm. 1, 2005, pp. 73-77 Universitat de Barcelona Barcelona, España Available in: http://www.redalyc.org/articulo.oa?id=50530108 How to cite Complete issue Scientific Information System More information about this article Network of Scientific Journals from Latin America, the Caribbean, Spain and Portugal Journal's homepage in redalyc.org Non-profit academic project, developed under the open access initiative Geologica Acta, Vol.3, Nº1, 2005, 73-77 Available online at www.geologica-acta.com Reply G. ACEÑOLAZA CONICET- INSUGEO Miguel Lillo 205, 4000 Tucumán, Argentina. E-mail: [email protected] INTRODUCTION of publications in different media resulted in the “rather convolute story frequently going back and forth” men- A recent discussion by Buatois and Mángano on the tioned by them, where updated information published article published in the special volume “Advances in the mostly as short papers and abstracts came out before the knowledge of the Cambrian System” (Aceñolaza, 2003a), discussed paper. Aceñolaza and Aceñolaza (2001) is a focused on several geological aspects of the Cambrian clear example of this situation, where a short paper pre- sequences in northern Argentina. I would like to express sented at the 2001 field meeting of the Subcommission my gratitude to the early referred authors for some inte- held in China, one year after the Argentine meeting, was resting observations made regarding the paper, that origi- published before the discussed paper. nally had as a goal to provide wide bibliographical data for those readers interested in these South American Some aspects related to the discussion done by Bua- sequences. tois and Mángano shall be clarified as follows: Unfortunately, I believe that this information was made available rather late in the processing of the manu- PUNCOVISCANA FORMATION (S.L.) script. After almost three years of the original handling of revised papers, some of the ideas discussed and data Most of the observations are figure based analysis. As observed are considered in a similar direction. Buatois stated by Buatois and Mángano, tackling such a complex and Mángano have based their discussions and judge- topic in a perfect manner giving summarized stratigraphi- ments, mostly on data fully published after the acceptance cal and temporal schemes for a basin with different of the final paper (Buatois and Mángano, 2003a, b and c; lithologies and ages over 400 000 km2 is strictly not pos- Buatois et al., 2003; Mángano and Buatois, 2003a and b; sible. As expected, time lines will cut different units, Mángano and Buatois, 2004; Mángano and Buatois, in facies and lithologies included in the Puncoviscana For- press). Besides, some aspects of the Cambrian sequences mation (s.l), depending on the relative basinal position of of North-western Argentina have been clarified in later the analyzed material. All figures are referred as “sketch”, publications(Aceñolaza and Aceñolaza, 2001, 2003; a terminology that allows a certain generalization. Most Aceñolaza, 2004). figures were taken and slightly adapted from early publi- cations, in the same manner as Buatois and Mángano did The original special volume was published as a result as main co-authors in Aceñolaza et al. (1999), supporting of the VI field meeting of the Subcommission on Cambri- the ideas of this paper one year before the Argentine an Stratigraphy (IUGS) held in Argentina in the year meeting. Some figures are shared and adapted from the 2000. The papers were finally published in March 2003. mentioned publication. As stated by Buatois and Mángano, views on these topics are changing at a very fast pace, based on an important Under the denomination of Puncoviscana Formation number of publications during the last years. This amount (s.l.) we understand a series of lithologies, from slates to © UB-ICTJA 73 G. ACEÑOLAZA The Cambrian System in NW Argentina. Reply conglomerates and limestones, clearly different one from paragraph states that the age of the Mesón Group ranges another. Limestones, conglomerates and shales, to men- between the Lower and Upper Cambrian, highlighting the tion some facies represented in the unit, do not sediment incongruity on the data provided by fossiliferous informa- under the same paleoenvironmental conditions, so it is tion included in their different units. Syringomorpha incorrect to believe all the Puncoviscana Formation (s.l.) nilssonni is mentioned in the Campanario Formation as as deposited entirely in a deep water setting. To detail on one of the problematic biostratigraphic data. obvious subjects will generate “phraseology”, a common practice already noticed by Keighley (2002) in Buatois and Buatois and Mángano added that the trilobite men- Mángano. Most trace fossils were historically recovered tioned by Aceñolaza (1973) and Aceñolaza and Bor- from interpreted deep sea facies, as recently referred by donaro (1990) has been recently reassigned to Leioste- Buatois and Mángano (2003b), resulting in a frequent men- gium douglassi by Vaccari and Waisfeld (2000). Fossil tion of this environmental setting. In the last mentioned material is housed in the Invertebrate Paleontological paper, authors recall a publication by Aceñolaza et al. (1999) Collections of the Facultad de Ciencias Naturales and as “deposited entirely in deep submarine fans” (sic.). Con- Instituto Miguel Lillo (where I am the curator) and has trary to what was claimed by Buatois and Mángano (2003b, never been asked for loan neither by the authors of the p. 572), Aceñolaza et al. (1999) have never documented or review nor by Buatois and Mángano. mentioned an exclusive deep water setting. In a similar man- ner, Buatois and Mángano (2003b, p. 573) mentioned that Neither the data given on page 28 with the reference “ongoing studies” suggest an eastern shallow-marine facies in the text to Syringomorpha and the “Asaphiscus- while to the west deep-marine environments were deve- Leiostegium” dilemma is mentioned by Buatois and loped. A shallower area was already clearly interpreted and Mángano in their discussion. Facts have been only par- figured during the last century by Borrello (1969, p. 55, 60). tially presented to the readers. “Impact papers” refreshing ideas born during the 60´s as own will not solve the problems in the Cambrian siliciclastic Concerning the presence of the Santa Rosita Forma- sequences of NW Argentina. tion in Azul Pampa locality, again, they are arguing with recent field work and data not available at that moment. In addition, it is incorrect to believe that all the Punco- Today, own observations support the existence at that viscana Formation shall be restricted to the Lower Cam- locality of a lower quartzitic member within the Santa brian as stated by Mángano and Buatois (Nemakit-Dal- Rosita Formation (referred to the partially equivalent dynian). The depositional and diagenetical age is still Casayoc Formation). controversial. Most probably, a Lower Cambrian age could be used only if referred strictly to the ichnofossili- Environments represented in the Mesón Group were ferous strata and the unit defined by Turner (1960, sensu described by several authors and mentioned in the text of stricto). If the Puncoviscana Formation is considered on pages 27-28 (Moya, 1998; Sánchez, 1999; Sánchez and its generalized use, unifying different lithologies and out- Salfity, 1999), so it is clear that a translation mistake crops (sensu lato), it should be considered Precambrian – referred the strata to a shoreline. Most of the deposition Lower Cambrian. Adams et al. (1990), Do Campo et al. of the Mesón and Santa Victoria groups took place on a (1994) and Do Campo (1999) presented K-Ar data shoreface setting as stated in different parts of the dis- reflecting older ages of deposition and diagenesis, rang- cussed publication and in several papers (Moya, 1988, ing from 545 to >670 +/- 27 Ma. Finally, if we consider 1998 and 1999; Aceñolaza, 1996; Aceñolaza and Poiré, C-isotope stratigraphy as one of the most powerful tools 1999; Aceñolaza and Aceñolaza, 2002; Di Cunzolo et al., in Precambrian chronostratigraphy, specially when sedi- 2003). ments lack recognizable animal fossils (Kaufman, 1988), we shall mention that Sial et al. (2001) have recently ana- lyzed the C and Sr isotopic evolution of a limestone unit SANTA VICTORIA GROUP included in the Puncoviscana Formation, concluding that the Precambrian / Cambrian transition should be placed As stated by Buatois and Mángano, the Iruya uncon- within the upper sector of the limestone facies. “Filtered” formity separates the Mesón and Santa Victoria groups geochronologic data is used by Buatois and Mángano in (lapsus calamis), while the Tilcara unconformity is placed their contributions and discussion. below, separating the Puncoviscana Formation from the Mesón Group as correctly placed in fig. 2 of page 25. Old and recent publications by the author support the exis- MESÓN GROUP tence of this Iruya unconformity, supporting an erosional unconformity related to a sea level fall in a same manner Again, data is analyzed by means of the scheme of than Moya (1988, 1998) and Buatois et al. (2000). Inter- fig. 2, and not with the written text. On page 28, the last estingly, Aceñolaza (1996) almost ten years ago named Geologica Acta, Vol.3, Nº1, 2005, 73-77 74 G. ACEÑOLAZA The Cambrian System in NW Argentina. Reply the sea level fall responsible for the Iruya unconformity Erdogan et al., 2004 see Skolithos traffic –on line forum as “Iruya Eustatic Event”, data well known but never on trace fossils–). Phycodes was included in Trichopy- mentioned by Buatois and Mángano. cus (Geyer and Uchman, 1995) and later in Treptichnus (Jensen et al., 2000). However, Erdogan et al. (2004) New interdisciplinary field work on this unconformi- mentioned that “separation of open burrows and feeding ty supports a fourth possibility that could be added to structures in Treptichnus should be made at first with all the three original interpretations considered by Buatois taxonomic consequences of this treatment”.
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