Centuries of Marine Radiocarbon Reservoir Age Variation Within Archaeological Mesodesma donacium Shells From Southern Peru

Mollusk shells provide brief (\u3c5 yr per shell) records of past marine conditions, including marine radiocarbon reservoir age (R) and upwelling. We report 21 14C ages and R calculations on small (~2 mg) samples from 2 Mesodesma donacium (surf clam) shells. These shells were excavated from a semi-subterranean house floor stratum 14C dated to 7625 ± 35 BP at site QJ-280, Quebrada Jaguay, southern Peru. The ranges in marine 14C ages (and thus R) from the 2 shells are 530 and 170 14C yr; R from individual aragonite samples spans 130 ± 60 to 730 ± 170 14C yr. This intrashell 14C variability suggests that 14C dating of small (time-slice much less than 1 yr) marine samples from a variable-R (i.e. variable-upwelling) environment may introduce centuries of chronometric uncertainty

El Nin˜o Impact on Mollusk Biomineralization: Implications for Trace Element Proxy Reconstructions and the Paleo-Archeological Record

Marine macroinvertebrates are ideal sentinel organisms to monitor rapid environmental changes associated with climatic phenomena. These organisms build up protective exoskeletons incrementally by biologically-controlled mineralization, which is deeply rooted in long-term evolutionary processes. Recent studies relating potential rapid environmental fluctuations to climate change, such as ocean acidification, suggest modifications on carbonate biominerals of marine invertebrates. However, the influence of known, and recurrent, climatic events on these biological processes during active mineralization is still insufficiently understood. Analysis of Peruvian cockles from the 1982–83 large magnitude El Nin˜o event shows significant alterations of the chemico-structure of carbonate biominerals. Here, we show that bivalves modify the main biomineralization mechanism during the event to continue shell secretion. As a result, magnesium content increases to stabilize amorphous calcium carbonate (ACC), inducing a rise in Mg/Ca unrelated to the associated increase in sea-surface temperature. Analysis of variations in Sr/Ca also suggests that this proxy should not be used in these bivalves to detect the temperature anomaly, while Ba/Ca peaks are recorded in shells in response to an increase in productivity, or dissolved barium in seawater, after the event. Presented data contribute to a better understanding of the effects of abrupt climate change on shell biomineralization, while also offering an alternative view of bivalve elemental proxy reconstructions.Furthermore, biomineralization changes in mollusk shells can be used as a novel potential proxy to provide a more nuanced historical record of El Nin˜o and similar rapid environmental change events

Integration of ancient DNA with transdisciplinary dataset finds strong support for Inca resettlement in the south Peruvian coast

Ancient DNA (aDNA) analysis provides a powerful means of investigating human migration, social organization, and a plethora of other crucial questions about humanity’s past. Recently, specialists have suggested that the ideal research design involving aDNA would include multiple independent lines of evidence. In this paper, we adopt a transdisciplinary approach integrating aDNA with archaeological, biogeochemical, and historical data to investigate six individuals found in two cemeteries that date to the Late Horizon (1400 to 1532 CE) and Colonial (1532 to 1825 CE) periods in the Chincha Valley of southern Peru. Genomic analyses indicate that these individuals are genetically most similar to ancient and present-day populations from the north Peruvian coast located several hundred kilometers away. These genomic data are consistent with 16th century written records as well as ceramic, textile, and isotopic data. These results provide some of the strongest evidence yet of state-sponsored resettlement in the pre-Colonial Andes. This study highlights the power of transdisciplinary research designs when using aDNA data and sets a methodological standard for investigating ancient mobility in complex societies

Centuries of Marine Radiocarbon Reservoir Age Variation within Archaeological Mesodesma donacium Shells from Southern Peru

From the 20th International Radiocarbon Conference held in Kona, Hawaii, USA, May 31-June 3, 2009.Mollusk shells provide brief (5 yr per shell) records of past marine conditions, including marine radiocarbon reservoir age (R) and upwelling. We report 21 14C ages and R calculations on small (~2 mg) samples from 2 Mesodesma donacium (surf clam) shells. These shells were excavated from a semi-subterranean house floor stratum 14C dated to 7625 +/- 35 BP at site QJ-280, Quebrada Jaguay, southern Peru. The ranges in marine 14C ages (and thus R) from the 2 shells are 530 and 170 14C yr; R from individual aragonite samples spans 130 +/- 60 to 730 +/- 170 14C yr. This intrashell 14C variability suggests that 14C dating of small (time-slice much less than 1 yr) marine samples from a variable-R (i.e. variable-upwelling) environment may introduce centuries of chronometric uncertainty.The Radiocarbon archives are made available by Radiocarbon and the University of Arizona Libraries. Contact [email protected] for further information.Migrated from OJS platform February 202

Seasonal Variations in Peruvian Marine Reservoir Age from Pre-Bomb Argopecten Purpuratus

From the 19th International Radiocarbon Conference held in Keble College, Oxford, England, April 3-7, 2006.Marine upwelling along coastal Peru can be intense and variable, making radiocarbon dating marine and coastal systems complex. Historical and proxy records of upwelling along coastal Peru are few, and long-lived species such as corals do not grow in the cold coastal waters. Mollusk shell carbonate, however, can record both the magnitude of the local marine reservoir correction, Delta-R, and of seasonal oscillations in the ventilation age of coastal waters. If large, these seasonal oscillations would complicate radiocarbon dating of marine organisms. To examine this possibility, we sampled for d13C, delta-18O, and 14C content a set of pre-bomb Argopecten purpuratus shells collected from coastal Peru during 1908 and 1926. Intrashell variations of up to 216 14C yr were noted, but these were not consistently correlated with seasonal changes in delta-18O or d13C. Only an 11 yr difference was observed in the weighted average Delta-R of Callao Bay shells collected during normal (1908) and El Nio (1926) years. Despite the intrashell 14C variation noted, weighted average Delta-R values from all 3 sample sites and from normal and El Nio years all overlap at 1 sigmaWe report Delta-R values of 183 +/- 18 and 194 +/- 23 yr from Callao Bay (124'S), 165 +/- 24 yr from Salaverry (8 degrees 14'S), and 189 +/- 23 yr from Sechura Bay (5degrees 45'S).The Radiocarbon archives are made available by Radiocarbon and the University of Arizona Libraries. Contact [email protected] for further information.Migrated from OJS platform February 202

Seasonal Variations in Peruvian Marine Reservoir Age from Pre-Bomb Argopecten purpuratus Shell Carbonate

From the 19th International Radiocarbon Conference held in Keble College, Oxford, England, April 3-7, 2006.Marine upwelling along coastal Peru can be intense and variable, making radiocarbon dating marine and coastal systems complex. Historical and proxy records of upwelling along coastal Peru are few, and long-lived species such as corals do not grow in the cold coastal waters. Mollusk shell carbonate, however, can record both the magnitude of the local marine reservoir correction, Delta-R, and of seasonal oscillations in the ventilation age of coastal waters. If large, these seasonal oscillations would complicate radiocarbon dating of marine organisms. To examine this possibility, we sampled for d13C, delta-18O, and 14C content a set of pre-bomb Argopecten purpuratus shells collected from coastal Peru during 1908 and 1926. Intrashell variations of up to 216 14C yr were noted, but these were not consistently correlated with seasonal changes in delta-18O or d13C. Only an 11 yr difference was observed in the weighted average Delta-R of Callao Bay shells collected during normal (1908) and El Nio (1926) years. Despite the intrashell 14C variation noted, weighted average Delta-R values from all 3 sample sites and from normal and El Nio years all overlap at 1 sigmaWe report Delta-R values of 183 +/- 18 and 194 +/- 23 yr from Callao Bay (124'S), 165 +/- 24 yr from Salaverry (8 degrees 14'S), and 189 +/- 23 yr from Sechura Bay (5degrees 45'S).The Radiocarbon archives are made available by Radiocarbon and the University of Arizona Libraries. Contact [email protected] for further information.Migrated from OJS platform February 202

Peruvian mollusk shells as multi-proxy archives: late Holocene upwelling variation and El Niño-induced biomineralization effects on trace elements

The purpose of this research is to characterize Peruvian upwelling during the late Holocene (last 2000 years) using molluscan proxies. Peruvian upwelling is a key component of El Niño/Southern Oscillation (ENSO) cycle, an important factor introducing interannual variability to Earth's weather. Thus by studying Peruvian paleoupwelling a better picture of past ENSO conditions can be inferred. High resolution sampling for radiocarbon and stable oxygen isotopes in modern pre-bomb Donax obesulus and Protothaca asperrima shells revealed sub-seasonal variations in Peruvian upwelling. Based on the shells' radiocarbon data a new reservoir effect correction (ΔR) was calculated for the Peruvian coast. ΔR, the radiocarbon age difference between global and local marine reservoirs, is also a qualitative proxy for deep water upwelling. A Trachycardium procerum shell that survived the 1982-1983 El Niño revealed that biomineralization changes induced by this event likely affected trace element incorporation into molluscan aragonite. Detected variations in mollusk biomineralization linked to El Niño suggest the need for coupled structural and chemical analyses in environmental proxy studies. Comparison between modern pre-bomb and archaeological ΔR obtained from D. obesulus shells revealed similar upwelling rates in northern Peru for the 20th and 16th centuries and lower rates for the 6th century. Low upwelling rates in northern Peru in the 6th century are in agreement with reported Mega- El Niño events that contributed to the political decline of Moche society. (Published By University of Alabama Libraries

El Niño Impact on Mollusk Biomineralization–Implications for Trace Element Proxy Reconstructions and the Paleo-Archeological Record

<div><p>Marine macroinvertebrates are ideal sentinel organisms to monitor rapid environmental changes associated with climatic phenomena. These organisms build up protective exoskeletons incrementally by biologically-controlled mineralization, which is deeply rooted in long-term evolutionary processes. Recent studies relating potential rapid environmental fluctuations to climate change, such as ocean acidification, suggest modifications on carbonate biominerals of marine invertebrates. However, the influence of known, and recurrent, climatic events on these biological processes during active mineralization is still insufficiently understood. Analysis of Peruvian cockles from the 1982–83 large magnitude El Niño event shows significant alterations of the chemico-structure of carbonate biominerals. Here, we show that bivalves modify the main biomineralization mechanism during the event to continue shell secretion. As a result, magnesium content increases to stabilize amorphous calcium carbonate (ACC), inducing a rise in Mg/Ca unrelated to the associated increase in sea-surface temperature. Analysis of variations in Sr/Ca also suggests that this proxy should not be used in these bivalves to detect the temperature anomaly, while Ba/Ca peaks are recorded in shells in response to an increase in productivity, or dissolved barium in seawater, after the event. Presented data contribute to a better understanding of the effects of abrupt climate change on shell biomineralization, while also offering an alternative view of bivalve elemental proxy reconstructions. Furthermore, biomineralization changes in mollusk shells can be used as a novel potential proxy to provide a more nuanced historical record of El Niño and similar rapid environmental change events.</p> </div

<i>In situ</i> Raman spectroscopy data.

<p>Specimens 2TP4-3 (A) and 2TP4-4 (B) showing shell regions precipitated during (a), around the scar (b), and after (c) the 1982–1983 El Niño event. Top image showing the shell with individual measurements with the shell scar (dashed lines) as a reference, and the bottom image with the corresponding Raman shift peaks. Peaks [arrows] at 1135 cm⁻¹ and 1523 cm⁻¹, due to (ν₂) C-C single bonds and (ν₁) C = C double bonds respectively, and the corresponding overtone bands at 2270 cm⁻¹ and 2645 cm⁻¹, disappear at the shell regions coincident with the maximum SST anomaly until normal biomineralization conditions resume after El Niño event.</p