We highlight a watershed in the natural gas legacy of the Netherlands: after 50 years of successful gas development, production output of conventional fields will decline from 2010 onwards. The projected decline in Dutch gas output will lead to a loss of future income for the State. In the past, E&P companies were prepared to compete for access to Dutch assets and lead in research as well as in the exploration for the development of conventional gas resources. Today, this cannot be assumed for the development of unconventional resources. It is not clear from our current state of knowledge whether the riskier unconventional gas resources in the Netherlands will be attractive for E&P companies. For example, are the financial risks for maturing potential unconventional resources into economic proved reserves acceptable to them? The US boom in unconventional gas production was preceded by government sponsored research programmes that stimulated the development of unconventional gas production technology. Decline in domestic gas production in the Netherlands therefore prompts for a dedicated upstream gas research programme. This will help to unlock future value from stranded conventional gas and unexplored unconventional gas resources. If such new gas resources can indeed be developed with the aid of research, undue loss of state income can be mitigated, which makes such a programme a compelling business case.

Three nothosaur skulls from the Lower Muschelkalk (Lower Anisian) locality of Winterswijk, the Netherlands, were recently acquired by museum Twentse Welle (Enschede) and have thereby become available for scientific description. Thus, these skulls had been identified as Nothosaurus winterswijkensis, but upon examination these skulls challenge the status of this Nothosaurus species. All diagnostic characters are somehow discredited, but the material can also not be unequivocably be considered as Nothosaurus marchicus, which is the only other obvious candidate. As these fossils originate from the same strata as the type of Nothosaurus winterswijkensis and there is no reason to assume that the animals occupied different ecological niches they are more plausibly considered one species, and Nothosaurus winterswijkensis therefore becomes a junior synonym of Nothosaurus marchicus. The diagnosis of Nothosaurus marchicus is enlarged to include all finds.

The chronostratigraphic position of aeolian dunes in East Flanders (Belgium) has been under debate for decades. Until now, the only available age information consisted of a limited number of radiocarbon dates, which provided indirect sediment deposition chronologies. This paper reports on the first direct determination, by quartz-based single-aliquot optically stimulated luminescence dating, of the time that dune sands were deposited along the Lower River Scheldt in Belgium. The sediments are dated at 12.0±0.9 ka (n = 5), which confirms that the time of inland dune formation in East Flanders dates from the Younger Dryas period and should not be constrained to the Holocene.

Accurate dating is necessary to get insight in the temporal variations in sediment deposition in floodplains. The interpretation of such dates is however dependent on the fluvial architecture of the floodplain. In this study we discuss the fluvial architecture of three contrasting Belgian catchments (Dijle, Geul and Amblève catchment) and how this influences the dating possibilities of net floodplain sediment storage. Although vertical aggradation occurred in all three floodplains during the last part of the Holocene, they differ in the importance of lateral accretion and vertical aggradation during the entire Holocene. Holocene floodplain aggradation is the dominant process in the Dijle catchment. Lateral reworking of the floodplain sediments by river meandering was limited to a part of the floodplain, resulting in stacked point bar deposits. The fluvial architecture allows identifying vertical aggradation without erosional hiatuses. Results show that trends in vertical floodplain aggradation in the Dijle catchment are mainly related to land use changes. In the other two catchments, lateral reworking was the dominant process, and channel lag and point bar deposits occur over the entire floodplain width. Here, tracers were used to date the sediment dynamics: lead from metal mining in the Geul and iron slag from ironworks in the Amblève catchment. These methods allow the identification of two or three discrete periods, but their spatial extent and variations is identified in a continuous way. The fluvial architecture and the limitation in dating with tracers hampered the identification of dominant environmental changes for sediment dynamics in both catchments. Dating methods which provide only discrete point information, like radiocarbon or OSL dating, are best suited for fluvial systems which contain continuous aggradation profiles. Spatially more continuous dating methods, e.g. through the use of tracers, allow to reconstruct past surfaces and allow to reconstruct reworked parts of the floodplain. As such they allow a better reconstruction of past sedimentation rates in systems with important lateral reworking.

In May 2009, Orson van de Plassche sadly passed away. In a paper of which parts, especially the discussion section, were written after his death, new data and a revision of an existing sea-level curve are presented for the Rotterdam area (Van de Plassche et al., 2010). This comment concerns two topics addressed in the discussion section: 1) connection of their revised Rotterdam relative sea-level curve for the period 7900-5300 cal yr BP (MSL-R2; Jelgersma, 1961; Van de Plassche, 1982; 1995; Berendsen et al., 2007; Van de Plassche et al., 2010) to the sea-level curve for the same area for the period 9000-7500 cal yr BP (MSL-R1; Hijma & Cohen, 2010); 2) The role of the river gradient on the calculation of the magnitude of a sea-level jump that occurred between 8450-8250 cal yr BP (Hijma & Cohen, 2010).

First of all, we want to stress that this reply to the comment by Hijma & Cohen on the paper by Van de Plassche et al. (2010) reflects our personal view and not necessarily the opinion of the first author of the paper under discussion, Orson van de Plassche. After a long career dedicated to sea-level research, Orson passed away on May 4, 2009, and left us with the Vlaardingen data set and his explicit wish to publish this material, which ultimately led to the Van de Plassche et al. (2010) paper. In the present paper we will: (1) give some background information on the Vlaardingen data set and the special circumstances under which the Van de Plassche et al. (2010) paper was written; (2) reply to the comment on the construction of our revised mean sea-level curve (MSL-R2); (3) reply to the comment on our suggestion that the palaeoriver-gradient might influence sea-level jump magnitude calculations.

The paper by Van de Plassche et al. (2010) is primarily based on the Vlaardingen data set that was collected by Orson van de Plassche in the mid-1980s, in a sequel to his PhD project (Van de Plassche, 1982). Soon after the start of the Vlaardingen project Orson became busily occupied with sea-level research in North America, leaving the Vlaardingen data set virtually unpublished (some data were published in Van de Plassche (1995)).