Post-depositional subsidence of the Avellino tephra marker bed in the Pontine plain (Lazio, Italy):Implications for Early Bronze Age palaeogeographical, water level and relative sea level reconstruction

Land subsidence has played and is still playing a significant role in coastal wetlands worldwide and in palaeogeographical reconstructions of such wetlands. The varying thickness of compaction-prone sediments over a stable subsurface is a key factor in determining its magnitude and in locating the most affected areas. In the coastal low-lying Agro Pontino (Lazio, Italy), subsidence of the past 90 years has been mapped using historical elevation data. Due to the fortunate preservation of distal Avellino tephra (AV-tephra, ca. 1900 cal. BCE) within its marshy strata, discovered a decade ago, detailed palaeogeographical reconstruction of the landscape in preparation for an assessment of its land use suitability in the Early Bronze Age (EBA) was possible. Current altitude variations of water-lain tephra in lake areas assumed to be connected necessitated a closer look at its original deposition altitude and the role of post-depositional subsidence. Recent subsidence patterns proved very useful for distinguishing stable from subsidence-prone areas. Two different EBA palaeo lake environments are distinguished: an inland and a near-coastal lake. The AV-tephra altitude variation within these lakes partly marks differential post-depositional subsidence within these lakes. Calculation of initial ripening of tephra-bearing lake deposits on top of shallowly buried Pleistocene ridges allowed for an estimation of original tephra deposition altitudes and associated lake levels. For the inland lake, a wide lake edge zone between 0.5 and 2 m above current sea level (m asl) was reconstructed, where EBA habitation or land use was possible. At the near-coastal lake, a water level of −1.5 to −1.3 m asl at the time of AV-tephra deposition was constrained. Because tephra deposition occurred here just after marine influence ceased, this altitude range is proposed to be a Relative Sea Level (RSL) index point at the time of AV-tephra deposition. The altitude range is in agreement with RSL models for tectonically stable areas in this region. The importance of subsidence in palaeogeographical, water level and RSL reconstructions in the region is stressed

Patterns of Middle and Upper Palaeolithic land use in Central Lazio (Italy)

Geo-archaeolog

Block copolymers confined in a nanopore: Pathfinding in a curving and frustrating flatland

We have studied structure formation in a confined block copolymer melt by means of dynamic density functional theory (DDFT). The confinement is two-dimensional, and the confined geometry is that of a cylindrical nanopore. Although the results of this study are general, our coarse-grained molecular model is inspired by an experimental lamellae-forming PS-PBD diblock copolymer system (Shin et al, Science, 306, 76 (2004)), in which an exotic toroidal structure was observed upon confinement in alumina nanopores. Our computational study shows that a zoo of exotic structures can be formed, although the majority, including the catenoid, helix and double helix that were also found in Monte Carlo (MC) nanopore studies, are metastable states. We introduce a general classification scheme and consider the role of kinetics and elongational pressure on stability and formation pathway of both equilibrium and metastable structures in detail. We find that helicity and three-fold connections mediate structural transitions on a larger scale. Moreover, by matching the remaining parameter in our mesoscopic method, the Flory-Huggins parameter, to the experimental system, we obtain a structure that resembles the experimental toroidal structure in great detail. Here, the most important factor seems to be the roughness of the pore, i.e. small variations of the pore radius on a scale that is larger than the characteristic size in the system.Comment: The following article has been accepted by JCP. After it is published, it will be found at http://jcp.aip.org