Slope deposits in semiarid regions are known to be very sensitive environments, especially those that occurred during the minor fluctuations of the late Holocene. In this paper we analyse Holocene colluvium genesis, composition, and paleoenvironmental meaning through the study of slope deposits in NE Spain. Two cumulative slope stages are described during this period. In the study area, both slope accumulations are superimposed and this has enabled an excellent preservation of the aggregative sequence and the paleosols corresponding to stabilisation stages. 14C and TL dating, as well as archaeological remains, provide considerable chronological precision for this sequence. The origin of the accumulation of the lower unit is placed around 4295–4083 cal yr BP/2346–2134 cal yr BC (late Chalcolithic) and it developed until the Iron Age in a cooler and wetter climate (Cold Iron Age). Under favourable conditions, a soil A-horizon was formed on top of this unit. A new slope accumulation was formed during the Little Ice Age. Within the slope two morphogenetic periods ending with A-horizons are distinguished and related with two main cold–wet climatic events. The study of these slopes provides a great amount of data for the paleoenvironmental and geoarchaeological reconstruction of the late Holocene in NE Spain.

Slope deposits, in semiarid regions, are known to be very sensitive environments, especially those that occurred during the minor fluctuations of the late Holocene. In this paper we analyse Holocene colluvium genesis, composition, and paleoenvironmental meaning through the study of slope deposits at Peña Enroque (Ebro Depression, NE Spain). Two cumulative slope stages are described during this period in NE Spain. Both slope accumulations are superimposed and this has enabled an excellent preservation of the aggregative sequence and the paleosols corresponding to stabilisation stages. 14 C and TL dating, as well as archaeological remains, provide considerable chronological precision for this sequence. The origin of the accumulation of the lower unit is placed around 4295-4083 cal yr BP/2346-2134 cal yr BC (late Chalcolithic) and it developed until the Iron Age in a cooler and wetter climate (Cold Iron Age). Under favourable conditions, a soil A-horizon was formed on top of this unit. After a long erosive stage (Warm Roman Period, Medieval Climatic Anomaly), a new slope accumulation was formed during the Little Ice Age. Within the slope two morphogenetic periods are distinguished, both ending with A-horizons. Both periods can be related with the two main cold-wet climatic events in NE Spain.

We studied the fire record and its environmental consequences during the Holocene in the Central Ebro Basin. This region is very sensitive to environmental changes due to its semiarid conditions, lithological features and a continuous human presence during the past 6000 years. The study area is a 6 m buried sequence of polycyclic soils developed approximately 9500 years ago that is exceptionally well preserved and encompasses four sedimentary units. The content and size distribution of macroscopic charcoal fragments were determined throughout the soil sequence and the analysis of the composition of charcoal, litter and sediments via analytical pyrolysis (Py-GC/MS). The high amount of charcoal fragments recovered in most horizons highlights the fire frequencies since the beginning of the Neolithic, most of which were probably of anthropogenic origin. In some soil horizons where charcoal was not found, we detected a distribution pattern of lipid compounds that could be related to biomass burning. On the other hand, the low number of pyrolysates in the charcoal could be attributed to highintensity fires. No clear pattern was found in the composition of pyrolysates related to the age of sediments or vegetation type. The most ancient soil (Unit 1) was the richest in charcoal content and contains a higher proportion of larger fragments (> 4 mm), which is consistent with the burning of a relatively dense vegetation cover. This buried soil has been preserved in situ, probably due to the accumulation of sedimentary materials because of a high-intensity fire. In addition, the pyrogenic C in this soil has some plant markers that could indicate a low degree of transformation. In Units 2-4, both the amount of charcoals and the proportions of macrofragments > 4 mm are lower than those in Unit 1, which coincides with a more open forest and the presence of shrubs and herbs. The preservation of this site is key to continuing with studies that contribute to a better assessment of the consequences of future disturbances, such as landscape transformation and climate change.

Se da cuenta de la excavaciones en el yacimiento del Cabezo de la Cruz, en el valle de la Huerva, al sur de Zaragoza.

The polyphasic evolution of the testimonial buttes in the central area of the Ebro basin (Los Monegros) is analysed. This is a semiarid area that favours high erosion rates. An evolutionary model of the Jubierre hills is presented that shows the environmental cycles represented by aggradational and degradative processes on the slopes that resulted in the present arrangement of talus flatiron rings. In the four studied cases, talus relicts are composed of detritic material from a disappeared caprock pediment. Four slope stages (S4 to S1) that formed under stable climate conditions are identified. Older stages (S4 and S3) are estimated by comparison with other talus flatirons in the region. The S2 stage contains Bronze Age archaeological remains and the radiocarbon age obtained was 1608–1446 years cal BC (2σ), while S1 is younger. A palaeoenvironmental interpretation was made for these aggradational stages (S4 to S1). The active erosion of these hills led to a relief inversion, and talus flatirons remain as the only features revealing the presence of the relict hills and past human occupations.