Correction to: Late Neogene evolution of the Peruvian margin and its ecosystems: a synthesis from the Sacaco record.

[This corrects the article DOI: 10.1007/s00531-021-02003-1.].

Magmatic evolution of Panama Canal volcanic rocks: A record of arc processes and tectonic change.

Volcanic rocks along the Panama Canal present a world-class opportunity to examine the relationship between arc magmatism, tectonic forcing, wet and dry magmas, and volcanic structures. Major and trace element geochemistry of Canal volcanic rocks indicate a significant petrologic transition at 21-25 Ma. Oligocene Bas Obispo Fm. rocks have large negative Nb-Ta anomalies, low HREE, fluid mobile element enrichments, a THI of 0.88, and a H2Ocalc of >3 wt. %. In contrast, the Miocene Pedro Miguel and Late Basalt Fm. exhibit reduced Nb-Ta anomalies, flattened REE curves, depleted fluid mobile elements, a THI of 1.45, a H2Ocalc of <1 wt. %, and plot in mid-ocean ridge/back-arc basin fields. Geochemical modeling of Miocene rocks indicates 0.5-0.1 kbar crystallization depths of hot (1100-1190°C) magmas in which most compositional diversity can be explained by fractional crystallization (F = 0.5). However, the most silicic lavas (Las Cascadas Fm.) require an additional mechanism, and assimilation-fractional-crystallization can reproduce observed compositions at reasonable melt fractions. The Canal volcanic rocks, therefore, change from hydrous basaltic pyroclastic deposits typical of mantle-wedge-derived magmas, to hot, dry bi-modal magmatism at the Oligocene-Miocene boundary. We suggest the primary reason for the change is onset of arc perpendicular extension localized to central Panama. High-resolution mapping along the Panama Canal has revealed a sequence of inward dipping maar-diatreme pyroclastic pipes, large basaltic sills, and bedded silicic ignimbrites and tuff deposits. These volcanic bodies intrude into the sedimentary Canal Basin and are cut by normal and subsequently strike-slip faults. Such pyroclastic pipes and basaltic sills are most common in extensional arc and large igneous province environments. Overall, the change in volcanic edifice form and geochemistry are related to onset of arc perpendicular extension, and are consistent with the idea that Panama arc crust fractured during collision with South America forming the observed Canal extensional zone.

First North American fossil monkey and early Miocene tropical biotic interchange.

New World monkeys (platyrrhines) are a diverse part of modern tropical ecosystems in North and South America, yet their early evolutionary history in the tropics is largely unknown. Molecular divergence estimates suggest that primates arrived in tropical Central America, the southern-most extent of the North American landmass, with several dispersals from South America starting with the emergence of the Isthmus of Panama 3-4 million years ago (Ma). The complete absence of primate fossils from Central America has, however, limited our understanding of their history in the New World. Here we present the first description of a fossil monkey recovered from the North American landmass, the oldest known crown platyrrhine, from a precisely dated 20.9-Ma layer in the Las Cascadas Formation in the Panama Canal Basin, Panama. This discovery suggests that family-level diversification of extant New World monkeys occurred in the tropics, with new divergence estimates for Cebidae between 22 and 25 Ma, and provides the oldest fossil evidence for mammalian interchange between South and North America. The timing is consistent with recent tectonic reconstructions of a relatively narrow Central American Seaway in the early Miocene epoch, coincident with over-water dispersals inferred for many other groups of animals and plants. Discovery of an early Miocene primate in Panama provides evidence for a circum-Caribbean tropical distribution of New World monkeys by this time, with ocean barriers not wholly restricting their northward movements, requiring a complex set of ecological factors to explain their absence in well-sampled similarly aged localities at higher latitudes of North America.

Changes in forest biomass litter dynamics and soils following shifting cultivation in southern México: an overview

Se evaluó el impacto relativo de los condicionantes ambientales y los efectos del uso de la tierra a nivel de lotes, sobre procesos del ecosistema en un bosque tropical seco del sur de la Penísula de Yucatán, a través del muestreo a lo largo de gradientes naturales y hechos por el hombre. Los objetivos fueron 1)describir los gradientes ambientes naturales de precipitación y suelos en escala regional, 2)explorar la respuesta de propiedades clave y procesos del ecosistema a tales gradientes, y 3)comprender los efectos de la edad del bosque sobre lotes dentro de una región dada del gradiente. Se estudiaron la biomasa superficial (viva y detrítica), la producción y química de hojarasca, y los suelos. En cada uno de 3 sitios con un gradiente de lluvia estacional entre 900-1400 mm/año se muestraron 10 a 13 lotes, imcluyendo bosque secundario y maduro. La caída de hojarasca aumentó y su contenido de nutrientes bajó en el pico de la estación seca. En el bosque maduro los factores ambientales asociados al gradiente de precipitación limitaron la producción de hojarasca, biomasa y materia orgánica del suelo. La historia humana del área, incluyendo la tala y decisiones acerca de áreas no afectadas (p.e. vertientes altas), añadió información crítica para comprender diferencias en la biomasa superficial del bosque maduro. Todos los aspectos de estructura y función en bosques secundarios jóvenes (biomasa viva superficial, producción de hojarasca, masa en el piso y propiedades críticos del suelo) están fuertemente influenciadas por la edad del lote. La recuperación de los niveles de bosque maduro se estima conservadoramente en 55-95 años. P y/o N parecen limitar procesos esenciales del ecosistema como producción de hojarasca, descomposición y biomasa superficial. Se sugiere que una vez superada la limitación de agua, el P se hace limitante. La evidencia incluye mayor reabsorción de P de la hojarasca, una fuerte respuesta de la concentración de P, pero no de la de N, al gradiente de precipitación, y un aumento en la eficiencia de uso de P con el umento en la edad del lote. La presencia de humanos en el sur de Yucatán resulta en mayores cambios del ecosistema que aquellos inducidos por variación natural del ambiente en escala regional. Para comprender mejor estos paisajes y para llevar estudios puntuales a evaluaciones regionales y globales, resulta vital integrar los impactos humanos en los procesos del ecosistema