The Las Salinas palaeo-lagoon in the Sechura Desert (Peru): Evolution during the last two millennia

Abstract

International audienceThe Sechura Desert provides a unique example of a vast palaeo-lagoon system on the Peruvian coast that was active during the first millennium AD.Reconstruction of coastal evolution is made possible by the good resolution of the sedimentary records of the Las Salinas Noroeste coastal plain.Evidence from morphostratigraphy and sedimentary facies indicates marked environmental diversity between the 3rd and the 8th centuries AD and a wide variability of sedimentary dynamics: lagoon foreshores received alternately fine distal marine sediments and coarser continental sediments in pro-deltaic sheets. Evaporation phases periodically occurred in these foreshores causing the formation of salt crusts. After a last high water level in the 8th century AD, the lagoon ultimately dried out and remains dry today. The malacofauna and sedimentary facies indicate that marine marshes bordered by vegetation, perhaps mangrove, developed in the higher parts of these lagoons. This palaeogeography is explained by the progressive build-up of a sand bar which started at least in the middle Holocene. From the 3rd to 8th centuries AD, the lagoon had limited connection to the sea in its northern end and hosted a warm-water and productive ecosystem that was exploited by pre-Hispanic populations. Wetter conditions in the Andes and occasional El Niño rainfalls maintained the lagoon during this period. The freshwater input likely stopped in the 8th century AD, which led to the closing of the shore bar under the influence of the longshore drift rapidly followed by the drying up of the lagoon, and the abandonment of the archaeological site

Landscape Modifications ascribed to El Niño Events in Late pre-Hispanic Coastal Peru

“…14 documents identified by examination of the bibliography of the selected works have been added for the review analysis (Table 2), thus, a total of 70 documents were finally reviewed (Tables 3, 4). [20] WoS, Scopus Urpi Kocha Lagoon (Rio Lurin) Etayo-Cadavid et al ( 2013) [108] WoS, Scopus North and south coast of Moche mouth Hanzalova and Pavelka (2013) [109] Scopus Ciudad Perdida de Huayuri (upper Grande Valley) Macthle and Eitel (2013) [110] WoS, Scopus upper Grance Valley and middle Nazca Valley Kalicki et al ( 2014) [111] Scopus Lomas de Lachay (South of middle Huaura Valley) Nesbitt (2016) [112] WoS Caballo Muerto Archaeological Complex (middle Moche Valley) Caramanica and Koons (2016) [113] WoS, Scopus Pampa de Mocan (middle Jequetepeque Valley) Pavelka et al ( 2016) [114] WoS Cantalloc (upper Nazca Valley) Christol et al (2017) [115] WoS, Scopus West coast of La Leche mouth Wang et al (2017) [116] WoS Salar Grande, Chile Kalicki et al (2018) [117] WoS, Scopus Lomas de Lachay (South of middle Huaura Valley) Delle Rose et al (2019) [23] WoS, Scopus Cahuachi (middle Nazca Valley) Caramanica et al (2020) [118] WoS, Scopus Pampa de Mocan (middle Jequetepeque Valley) Kalicki and Kalicki (2020) [119] WoS Lomas de Lachay (South of middle Huaura Valley) Sandweiss et al (2020) [120] WoS, Scopus Review article Uceda et al (2021) [121] WoS, Scopus Review article Sandweiss and Maasch (2022) [122] WoS, Scopus Review article Rubinatto Serrano et al (2022) [123] WoS, Scopus Rio Muerto and 3 other sites (Moquegua Valley)…”

First Contributions of Charcoal Analysis to the Study of the Specialised Fishing Site of Bayovar-01 (5th–8th Centuries AD), Extreme Northern Coast of Peru

“…So, while the possibility that fuel wood resources could have been obtained over longer distances cannot be completely dismissed, it is more probable that they were collected locally. The only palaeo-environmental study carried out in this area indicates proxy data that in the past the local area around the palaeo-lagoon was characterised by tropical vegetation (even a mangrove type vegetation) during the first millennium AD (Christol et al 2016(Christol et al , 2017. Therefore, our hypothesis with regards to fuel wood acquisition cannot be considered directly with local palaeo-vegetation data.…”

“…This finding is in concordance with the existing evidence that environmental conditions around Bayovar-01 were quite different during the Pre-Hispanic occupation. The presence of a large palaeo-lagoon, resulting in increased water availability (Christol et al 2017), would have supported a dry tropical forest, like that found today on the periphery of the Sechura desert (and elsewhere along the Peruvian coast like the 'Bosque de Pomac' in the Lambayeque region), where water is more abundant (La Torre-Cuadros and Linares Palomino 2008). This dry tropical forest, whose main components are Mimosoideae, and P. pallida in particular, could have provided all of the firewood necessary for the different activities carried out in Bayovar-01, particularly for the processing of large quantities of fish.…”

“…AD 489 and 766, pointing to a rather short but continuous occupation of the site (Table 1). Radiocarbon ages measured on charcoals were calibrated with the IntCal13 calibration curve, and marine shell age was calibrated using the Marine13 calibration curve (the calculation for the reservoir age is further discussed in Christol et al 2017). The analysis of the fish remains, which included over 35,000 otoliths and more than one million other skeletal remains, shows an abundance of Mugil cephalus and Micropogonias altipinnis, as well as other fish species in minor proportions.…”

“…Located on a Pleistocene marine terrace, the site is separated from the sea by a 6 km wide flat depression called Las Salinas (Figure 1), where some parts are lower than sea level (Novoa Goicochea 1998). A multiproxy study carried out on this depression, including sediment and malacofauna analysis, demonstrated that it was originally a lagoon that eventually disappeared in the 8th century AD due to a long process of sedimentation and the closing of the opening to the ocean by a sand bar's growth (Christol et al 2016(Christol et al , 2017. It is also important to note that during times of abnormally high rainfall in the highlands and the coast, related to the ENSO phenomenon, the Sechura desert's depressions are inundated by permanent and usually dry watercourses, forming a network of temporary lakes with a combined area of more than 2000 km² (more than 7000 m 3 of water), that take years to dry out completely (Novoa Goicochea 1998).…”