Protection of coast and loss of the palaeontological heritage: the case of Punta Hermengo (Miramar, Buenos Aires Province)

Abstract

The aim of the present paper is to report the loss of the cultural and natural heritage of one of the most emblematic paleontological localities of Buenos Aires Province (Argentina). Buenos Aires have a large number of paleontological sites from the upper Cenozoic, which have been studied from more than a century. In this sense, the first geological and paleontological reference to Punta Hermengo was performed by Florentino Ameghino at the beginning of XXth century. The coastal cliffs extending (with some interruptions) from northern Mar del Plata to Bahía Blanca city (southeast of Buenos Aires Province) are particularly interesting, because they are the most complete record of the Pliocene-Pleistocene period. Among these, the cliffs atPunta Hermengo (Partido de General Alvarado) are outstanding. The geological,paleontological, and biostratigraphic aspects of this area have been studied in several scientific contributions. At present, several research projects are being conducted in the area of the littoral cliffs between Mar del Plata city and Quequén River, including those corresponding to the area of Punta Hermengo. The works will allow completing and testing the present chronostratigraphic scheme for the Pampean Region. Sedimentary sequences exposed at Punta Hermengo correspond to the Pleistocene (2.58 to 0.012 Ma). According to the current chronostratigraphic scheme, the units represented at Punta Hermengo correspond to the Ensenadan, Bonaerian, and Lujanian Stages/Ages. One of the most relevant aspects of the outcrops at Punta Hermengo is likely to be represented by their rich fauna, one of themost abundant and diverse Pleistocene assemblages known in our country. Other associations have been recovered from different areas of Buenos Aires province. However, some of them remain unknown (i.e. Centinela del Mar and Arroyo Chocorí), or are poorly diverse (e.g. San Pedro, Río Arrecifes, Ramallo, Necochea, Mar del Sur, Camet Norte, etc). The bottom half of the sequence at Punta Hermengo contains Ensenadan fossil remains being the best place for the study of this Stage/Age, because other localities with Ensenadan mammals are difficult to access and study (e.g. ?toscas del Río de La Plata? in the sorroundings of Capital Federal, Ensenada harbor), or are stratigraphically confuse (cliffs between Mar del Plata and Miramar). Within this context, Punta Hermengo was used for comparison and correlation with other associations, not only at a regional level but also at a continental level. According to several studies, geomorphologic characteristics of the zone indicate that the coast is of a cohesive erosional type, because it presents a very fragile stability and irreversible erosive processes. On the other hand, high activities of massive removal phenomena (such as rock falls and planar slip) are observed. Cliffs of the studied area are classified as either active or inactive. The natural evolution of the landscape shows erosion of the cliffs ledge and filling of the bays to rectify the coastline, and finally a regular retreat of the coastline. This dynamics is highly modified by anthropic alteration, performed directly or indirectly on the morphology of this outcrops (extraction of sand, urbanization, artificially fixed dunes, etc.). To avoid this retreat of Punta Hermengo cliffs, the Municipality of General Alvarado Countydecided to protect the coastline by placing quartzite blocks parallel to the cliffs, even along not urbanized areas. This has been recently noticed by the authors during a paleontological field work. Consequently all sampling efforts and collection of new paleontological specimens were frustrated due to the impossibility of accessing to prospect the basal levels with Ensenadan fauna. As noted by the authors, this type of activity is neither unique nor recent in the area; since 2006 similar ?barriers? were built to the north of Miramar (as part of the same municipal project) and a few years ago a singular paleontological and archeological site, located a few meters north of Punta Hermengo, close to the fishing pier, almost disappeared. This site, already mentioned by Carlos Ameghino at the beginning of the XXth century, was partially covered by remains of old road concrete and then by accumulation of sand from the beach generated by the construction of a breakwater. In addition, significantalterations have been detected on the cliffs of Centinela del Mar (ravine cuts off), Mar del Sur (cuts and constructions on the cliffs), and Las Brusquitas and Lobería streams (placement of quartzite blocks). With the arrival of the constructions mentioned before, the 100-years prospecting and recovery of vertebrate fossils were abruptly interrupted. Taking into account the decisions made by municipal authorities, the local museum will not be able to increase its natural heritage. A note was sent to ?Centro de Registro del Patrimonio Arqueológico y Paleontológico dependiente del Instituto Cultural de la Provincia de Buenos Aires? by two ofthe authors (ES y EPT) on September 20, 2007 (reception no. 2526), regarding the loss of the paleontological heritage of Punta Hermengo. No answer from the authorities has been received up to the present day. With the loss of this important historical and natural place, the cultural heritage, part of the bulwark that gives a sense of identity and pertinence to the community, will disappear. Consequently, we establish the need of declaring the coastal area between Mar del Sur and Centinela del Mar as a protected area on the coast of the Partido de General Alvarado.