Understanding Abrupt Climate Change in the Late Quaternary

During the late Quaternary period, a series of abrupt climate changes in the tropics and sub-tropics driven by changes in ocean circulation were both dramatic and disruptive.

Solar system exposure to supernova γ radiation

Planetary habitability may be affected by exposure to γ radiation from supernovae (SNe). Records of Earth history during the late Quaternary Period (40 000 years to present) allow testing for specific SN γ radiation effects. SNe include Type Ia white dwarf explosions, Type Ib, c and II core collapses, and many γ burst objects. Surveys of galactic SNe remnants offer a nearly complete accounting for this time and including SN distances and ages. Terrestrial changes in records of the cosmogenic isotope 14C are here compared to SN-predicted changes. SN γ emission occurs mainly within 3 years; average per-event total emissions of 4 × 1049 erg are used for comparison of close events There are 18 SNe ≤ 1.5 kpc, and brief 14C anomalies are reported for eight of the closest. Four are notable (BP is year before 1950 CE): the older Vela SNR and an abrupt 30‰ del 14C rise at 12 740 BP; S165 and a 20‰ rise at 7431 BP; Vela Jr. and a 14‰ rise at 2765 BP; and HB9 and a 9‰ rise at 5372 BP. Rapid-increase anomalies in 14C production have been attributed to cosmic rays from exceptionally large solar flares. However, the proximity and ages of these SNe, the probable size and duration of their γ emissions, the predicted effects on 14C, and the agreement with 14C records together support SNe causation. Also, the supposed solar-caused 14C anomalies at CE 774 and 993 may instead have been caused by the SNe associated with the G190.9-2.2 and G347.3-00.5 remnants. Both are of appropriate age and distance.

Luminescence chronology of fluvial and marine records from subsurface core in Kaveri delta, Tamil Nadu: Implications to sea level fluctuations

South-Eastern coastal plains of India experience some of the major delta formations of the Indian subcontinent majorly affected by fluctuations of the Indian summer monsoon (ISM) and sea level. Past shoreline signatures in the form of palaeo beach ridges in Kaveri delta (Tamil Nadu, India), suggest a wave-dominated delta and thus past sea-level variations affecting directly the sedimentary dynamics of the Kaveri river forcing the river to either aggrade or prograde. Chronostratigraphic and foraminiferal study of the 25 m deep sediment core taken 2.5 km onshore from Tamil Nadu coast, Kaveri delta shows evidence of changing coastline over the last 150 ka. Various units in the core reflect eight major phases of increased sea level (~3.4 ka, ~5.0 ka, 9–6 ka, 60–57 ka, 89–81 ka, ~102 ka,~121 ka and 143–140 ka) partly coinciding with the global climate cycles MIS 1, MIS 3, MIS 5, MIS 6 respectively during the late Quaternary period. During ~121 ka and 9–6 ka, direct signature of marine transgression is observed by the presence of foraminifera in the core location. The study also shows that the sea transgression during ~121 ka was much longer-lasting and higher than during 9–6 ka, even though not revealed in the Quaternary sea level curve given by previous authors. Depositional breaks are observed in the core during periods of lower sea levels as the river responded by incision. Total organic matter of the deposition between 9–6 ka was observed as high as 2.5–6% suggesting oxygen stressed conditions during the period.

Checklist of sand dune vegetation on the tropical southeastern Brazil coast

Restingas are mosaics of plant communities living on marine sand deposits of the late Quaternary period, located between the sea and the Atlantic Forest. This study presents the diversity of the vegetation of coastal sand dunes in the southeastern coast of Brazil. A floristic survey and bibliographic review of the nine restinga regions of Rio de Janeiro state was carried out, and information is presented about the habit, life form, dispersion syndrome, distribution, and biome occurrence of each species. Ninety-eight species were recorded, distributed among 81 genera and 38 families, of which the most diverse are Asteraceae (12 species), Poaceae (12 species), Fabaceae (11 species), and Rubiaceae (6 species). The majority of species have herbaceous habits and predominantly are camephyte-autochoric species. They present wide geographical distributions or are restricted to just some Brazilian states and are more similar to the Atlantic Forest biome.