Reply 15 jun

Abstract

The beach-ridge sequence of the Usumacinta-Grijalva delta borders a 300 km long section of the southern Gulf of Mexico coast. With around 500 beach ridges formed in the last 6500 years, the sequence is unsurpassed in the world in terms of numbers of individual ridges preserved, continuity of the record, and temporal resolution. We mapped and dated the most extensively accreted part of the sequence, linking six phases of accretion to river mouth reconfigurations and constraining their ages with 14 C and OSL dating. The geomorphological and sedimentological reconstruction relied on lidar data, coring transects, GPR measurements, grain-size analyses, and chemical fingerprinting of volcanic glass and pumice encountered within the beach and dune deposits. We demonstrate that the beach-ridge complex was formed under ample long-term fluvial sediment supply and shorter-term wave-and aeolian-modulated sediment reworking. The abundance of fluvially supplied sand is explained by the presence of easily weatherable Los Chocoyos ignimbrites from the ca. 84 ka eruption of the Atitlán volcano (Guatemala) in the catchment of the Usumacinta River. Autocyclic processes seem responsible for the formation of ridge-swale couplets. Fluctuations in their periodicity (ranging from 6-19 years) are governed by progradation rate, and are therefore not indicative of sea level fluctuations or variability in storm activity. The fine sandy beach ridges are mainly swash built. Ridge elevation, however, is strongly influenced by aeolian accretion during the time the ridge is located next to the beach. Beach-ridge elevation is negatively correlated with progradation rate, which we relate to the variability in sediment supply to the coastal zone, reflecting decadal-scale precipitation changes within the river catchment. In the southern Mexican delta plain, the coastal beach ridges therefore appear to be excellent recorders of hinterland precipitation.

Silicon Calorimeters

“…This technique, first explored in the linear collider framework (35), is now being studied for the forward calorimeter upgrade of the ALICE detector. The feasibility of using such a calorimeter has been demonstrated with a prototype containing 39 million pixels tested in particle beams (36). The prototype (Figure 9) has 24 layers of tungsten, each corresponding to 0.97X 0 .…”

Heterogeneous and Highly Dynamic Interface in Plastocyanin–Cytochrome f Complex Revealed by Site-Specific 2D-IR Spectroscopy

“…However, many others must interact with their partners with lower affinity to form transient complexes so as to ensure rapid turnover in their cellular function. 1,2 Dynamic complexes, for example, are formed by recognition domains for fast response in signaling networks and by electrontransfer (ET) proteins for mediating efficient electron transport in diverse processes, including photosynthesis and respiration. [3][4][5] The dynamic nature makes these protein complexes more challenging to investigate and describe, hindering the development of a complete mechanistic understanding of their function.…”