The aim of this paper is to present the archaeological data that allows us to characterise the agrarian practices of Roman farmers through the study of cultivated fields. To undertake this research, ...we designed an analytical strategy combining spatial analysis, microstratigraphic analysis through soil micromorphology and physical-chemical analyses of bulk soil samples, and archaeobotanical analyses including palynology, phytoliths and geochemical analysis. All this has allowed us to obtain data of interest for the reconstruction of agrarian land use and to establish a methodological basis for developing future research. This high-resolution, multiscalar, and multianalytical approach pursues to characterize these archaeological contexts to singularize intensive agricultural practices developed in terraced field. The creation of this Roman peasant landscape is related to a specific models of socioeconomic organisation of agricultural work based on the household and its workforce as a determining vector in agrarian intensification.
The toil of several million peasant farmers in Aztec Mexico transformed lakebeds and mountainsides into a checkerboard of highly productive fields. This book charts the changing fortunes of one Aztec ...settlement and its terraced landscapes from the twelfth to the twenty-first century. It also follows the progress and missteps of a team of archaeologists as they pieced together this story.
Working at a settlement in the Toluca Valley of central Mexico, the authors used fieldwalking, excavation, soil and artifact analyses, maps, aerial photos, land deeds, and litigation records to reconstruct the changing landscape through time. Exploiting the methodologies and techniques of several disciplines, they bring context to eight centuries of the region’s agrarian history, exploring the effects of the Aztec and Spanish Empires, reform, and revolution on the physical shape of the Mexican countryside and the livelihoods of its people. Accessible to specialists and nonspecialists alike, this well-illustrated and well-organized volume provides a step-by-step guide that can be applied to the study of terraced landscapes anywhere in the world.
The four authors share an interest in terraced landscapes and have worked together and on their own on a variety of archaeological projects in Mesoamerica, the Mediterranean, Poland, and the United Kingdom.
Marginalization and abandonment of paddy terraces are widespread, but their effects on the sustainability of subsequent agricultural production are still unknown. Hani Paddy Terraces, included in ...Globally Important Agriculture Heritage Systems, are threatened by paddy fields drainage. Here, changes in terrace structure, the productivity of topsoil (0–20 cm), and soil water holding capacity at 0–70 cm depth were determined in a case study of Hani Paddy Terraces in Amengkong River Basin in Yuanyang County in Southwestern China, which had been converted into dryland terraces for 2–14 years. Our results showed that: (1) The degree of terrace structures degradation exhibited a U-shaped curve with increasing time since draining, with those drained for 5–9 years having the best structure; (2) Soil productivity index decreased first and then increased with time after conversion; (3) Maximum water holding capacity at 0–70 cm soil depth dramatically decreased after conversion and such trend became increasingly obvious with increasing time since conversion. Our study revealed that drainage of paddy terraces along with associated changes in crop and field management led to an increase in soil productivity, but degradation of terrace structures and a decrease in water holding capacity will inhibit restoration to paddy terraces. These findings enhance the understanding of the biophysical changes due to marginalization in paddy terraces.
Within this context, the area at the foot of Mont Blanc stands out for several exceptional features, like the presence of terraces that shape the cultivable areas, contributing to generate a ...symbiotic ecosystem between architectural elements and vine plants. A system where the traditional pergola bassa structure becomes the natural extension of the terraces, characterizing the landscape with the alternation of dry stone walls and pergolas. A panorama where some elements are more frequently recognizable even if in different forms and functions, demonstrating a centuries-old ability in managing local materials to create a symbiotic relationship between the productive landscape and its surrounding area. For this reason, the study aims to develop some reflections on the possibility of safeguarding the aesthetic and typological identity of the traditional landscape as a fundamental - and not subsidiary - element of the quality of the product itself.
Faults on microcontinents record the dynamic evolution of plate boundaries. However, most microcontinents are submarine and difficult to study. Here, we show that the southern part of the Isla Ángel ...de la Guarda (IAG) microcontinent, in the northern Gulf of California rift, is densely faulted by a late Quaternary‐active normal fault zone. To characterize the onshore kinematics of this Almeja fault zone, we integrated remote fault mapping using high‐resolution satellite‐ and drone‐based topography with neotectonic field‐mapping. We produced 13 luminescence ages from sediment deposits offset or impounded by faults to constrain the timing of fault offsets. We found that north‐striking normal faults in the Almeja fault zone continue offshore to the south and likely into the nascent North Salsipuedes basin southwest of IAG. Late Pleistocene and Holocene luminescence ages indicate that the most recent onshore fault activity occurred in the last ∼50 kyr. These observations suggest that the North Salsipuedes basin is kinematically linked with and continues onshore as the active Almeja fault zone. We suggest that fragmentation of the evolving IAG microcontinent may not yet be complete and that the Pacific‐North America plate boundary is either not fully localized onto the Ballenas transform fault and Lower Delfin pull‐apart basin or is in the initial stage of a plate boundary reorganization.
Plain Language Summary
Earth's rocky outer layer is broken into several tectonic plates. These plates move against each other at plate boundaries, causing geologic hazards like earthquakes. The locations of plate boundaries also move through time by a process called plate boundary reorganization. Here, we examine Isla Ángel de la Guarda (IAG), an uninhabited island in the northern Gulf of California, to study a potential plate boundary reorganization between the Pacific and North America plates. We looked at the pattern and activity of faults on southern IAG to assess their connection to the current plate boundary. We found that the faults have a similar orientation to an active, offshore part of the plate boundary southwest of IAG and that onshore faults are also active because they cut layers of sand and gravel that were deposited less than 50,000 years ago. Active faults that align with the plate boundary may imply that both are presently linked. A possible result of this linkage is the reorganization of the Pacific‐North America plate boundary across IAG.
Key Points
On Isla Ángel de la Guarda, we map the normal, north‐striking, Almeja fault zone that projects into an active offshore basin
Luminescence ages from faulted terraces indicate late Quaternary fault activity
Similar orientation and extension direction suggest a kinematic linkage between the Almeja fault zone and the active offshore basin
Terrace formation processes can reflect the evolution of large rivers. The Hetao Basin is a floodplain of the Yellow River, and there are two to three terraces that extend E–W on the northern margin. ...Based on a detailed field geological survey and measurement of the terrace sections, combined with sedimentological and chronological analyses, we reconstructed the developmental processes of the three terraces and inferred that three river terraces were formed by the Yellow River. The OSL dating results show that the time of deposition of terrace 3 was prior to 118kaBP. Subsequently, the terrace began to experience incision and formed the geomorphic surface of terrace T3. Similarly, terrace 2 and terrace 1 were mainly deposited from ~109 and 59ka, respectively; and began to be incised prior to 71 and 46ka, respectively. The three terraces in the northern Hetao Basin are the products of the combined actions of climatic shifts and tectonic uplift. The Yellow River's evolutionary history in the Hetao area since the Late Pleistocene is discussed. Before about 120kaBP, the Yellow River may have flowed through the northern Hetao Basin. Between 110 and 70kaBP, the Yellow River experienced at least two changes between river and lake sedimentation. From 60 to 50ka, a very large river-connected lake of the Yellow River was developed in the Hetao Basin. After 50ka, the Hetao river-connected paleolake of the Yellow River gradually dried.
•The 2–3 terraces on the northern margin of the Hetao Basin were identified.•The developmental processes of the three terraces were reconstructed.•The 2–3 terraces were proved to be river terraces of the Yellow River.•The evolutionary history of the Yellow River in the Hetao area since Qp3 is discussed.
Submarine channel-related thin-bedded turbidites are deposited in environments such as external levees, internal levees, depositional terraces and at times of channel abandonment. Thin-bedded ...turbidites are defined as beds that are less than 10 cm thick, but the described environments can at times contain beds up to 100 cm thick which would be classified as medium- or thick-bedded. This paper addresses examples of these environments from the modern seafloor, outcrop and the subsurface to suggest criteria that assist in the differentiation of levees and terraces from an architectural, sedimentological, ichnological and hydrocarbon reservoir perspective. External levees confine channel belts and are elongate sedimentary deposits that are a product of over-spill of turbidity currents from the channel belt they confine. External levees often have predictable vertical, lateral and downstream changes in thickness and sand content but are commonly modified by collapse of the inner external levee into the channel, by collapse on the outer external levee, by sediment waves, and by interaction of external levees with topographic features such as other channels, other external levees, basin margins or previous slump/slide blocks, which can greatly modify the sand distribution within them.
A combination of internal levees, depositional terraces and slide blocks of external levee sediment make up thin-bedded turbidites within channel belts. We differentiate between wedge-shaped internal levees and topographically flat or subdued depositional terraces, whose differing geometries and sand distribution reflect the fact that the flow processes involved in the formation of these deposits are different. The characteristic wedge shape of an internal levee requires sufficient space within the channel belt for the over-spilling current to spread, decelerate and deposit the majority of its silt and sand grade suspended sediment before reaching the bounding topography of the channel belt. In the case of depositional terraces the space available in the channel belt is insufficient for the current to decelerate and deposit the majority of its sediment before reaching the bounding topography of the channel belt, creating confined sheet-like deposits.
External levees, internal levees and depositional terraces have distinct sedimentological characteristics such as sand bed thickness trends and sedimentary structures that can be used to distinguish them. Together with sedimentological characteristics, in some systems these thin-bedded turbidite deposits contain distinctive trace fossil assemblages, where channel proximal deposits such as proximal external levees, internal levees and depositional terraces can have much higher ichnodiversity than sand-rich channel axes and more mud-dominated outer external levees.
The depositional sites for internal levees and depositional terraces within channel belts can be formed by various processes such as entrenchment, point bar accretion, meander bend cut-off, channel margin failure, or changes in the flow parameters. These processes can result in elevated surfaces within the confines of the channel belt that subsequently become prone to the deposition of over-bank deposits.
The development and preservation of levees and terraces is closely related to the evolution of the channel belt as a whole, which is controlled both by allogenic mechanisms (such as sea-level fluctuations, changes in turbidity current size and sediment calibre, and changes in the equilibrium profile of the channel), and by autogenic mechanisms (such as channel avulsion and resulting knick-point migration). Where preserved in the rock record thin-bedded turbidites have been uncommon primary targets for hydrocarbon field development, since most efforts have focused on the channel-fills which have the highest proportion of sand. However, thin-bedded turbidites can contain large amounts of sand, of which individual beds can be very laterally continuous, and hence can make significant secondary reservoir targets.
•Levees have a wedge shape•External levees confine channel-belts, internal levees confine channels•Channel belt thin-bedded turbidites are internal levees and depositional terraces•Terraces are flat surfaces or deposits within channel-belts•Preservation of thin-bedded turbidites depends on channel belt evolution
This work analyses the chronology of fluvial terrace sequences of the two most important fluvial basins from central Spain draining to the Atlantic Ocean (Upper Tagus and Duero drainage basins). Both ...basins evolved under similar Mediterranean climatic conditions throughout the Pleistocene and present comparable number of fluvial terraces (16–17) after excluding the higher terrace levels of the Tagus (T1–T5) entrenched in the Raña surface. These higher “rañizo terraces” was formed in response to fan-head trenching in this high alluvial piedmont (+220 m) and therefore not properly controlled by Quaternary fluvial downcutting. The study accomplishes the implementation of multiple regression analyses for terrace height-age relationships. To transform relative terrace heights above the present river thalwegs (i.e. +100 m) in numerical ages a “height-age transference function” has been developed on the basis of preliminary statistical geochronological approaches proposed for Central Spain. The resultant height-age transference function gather 73 published geochronological data for terrace sequences, featuring a 3rd Order Polynomial Function (R2 0.90). This function describes the overall trend of valley downcutting for the last c. 2.3 Ma in Central Spain and is used to assign numerical ages to terrace levels at different relative elevation.
•Is analysed the chronology of fluvial terrace sequences in central Spain summarising existent Geochronological, faunal and Palaeolithic data.•3rd Order Polynomial Functions describe the overall trend of valley downcutting for the last c. 2.3 Ma in Central Spain.•The obtained Height-Age transference functions can be used to assign numerical ages to terrace levels at different relative elevation.
The fluvial archive literature is dominated by research on river terraces with appropriate mention of adjacent environments such as lakes. Despite modern sedimentary basins comprising a significant ...(>88%) volume of distributive fluvial systems, of which alluvial fans (>1 km, <30 km in scale) are a significant part, interaction with these environments tends to be neglected and discussed in separate literature. This paper examines the dynamic role of alluvial fans within the fluvial landscape and their interaction with river systems, highlighting the potential value of alluvial fans to the wider fluvial archive community. Published literature is used to examine both thematic and geographical based benefits of alluvial fan research that can assist understanding of Quaternary fluvial archives. 3 regional case studies are presented that illustrate the interaction between alluvial fan and river terrace archives at Quaternary time-scales at 3 different stages of landscape evolution. These are i) continuous mountain front alluvial fans interacting with a non incising but laterally eroding axial fluvial system; ii) alluvial fans which transition into fluvial terraces as sedimentary basins shift from net aggradation to net incision and iii) tributary-junction alluvial fans that develop predominantly within incising river valley systems. A simple conceptual model is proposed to summarise the dynamic role of alluvial fans within this landscape context. The alluvial fans act as potential ‘buffers’ between hillslopes and river terrace records under ‘top down’ climate-driven high sediment supply and alluvial fan aggradation, and ‘couplers’ during periods of less sediment (in relation to water) discharge and alluvial fan incision. These dynamics will change with the addition of ‘bottom up’ controls such as main river incision, which will typically enhance the coupling effect of both systems.
•Provides the first review paper linking alluvial fan research with research into fluvial archives.•Pulls together material from across sub-disciplines.•Fans act as important ‘buffers’ or ‘couplers’ within the fluvial landscape.•Fan/river interactions change in response to top down and bottom up system drivers.•Dynamic relationships described in a conceptual model of alluvial fan/river interactions.
PDF
