Ongoing Projects
Modelled dating of modelled dune stratigraphies
Attempts to reconstruct past changes in climate-related forcing of dryland landscapes are hampered by the lack of an adequate quantitative framework for understanding the production and interpretation of dated sedimentary records. In drylands, as in other environments, information on past forcing conditions is progressively modified, degraded and removed from the available stratigraphic record by a series of ‘filters’ involving changes in the primary forcing factors themselves, geomorphological processes and the sampling/dating procedures (see figure below).
Previous work focused on the production of a quantitative model that includes these effects, which was used to examine (theoretically) the nature of preserved dryland sedimentary records and their relationships to primary forcing conditions.
The main findings were:
A new data treatment method (termed Accumulation Rate Variability) was developed which provides an efficient proxy for accumulation rates, and therefore the intensity of aeolian activity, with significant improvements over existing date-frequency methods.
This work was published in the following paper, which contains a full description of the model and discussion of findings:
Bailey, R. M. and Thomas, D. S. G. (2014), A quantitative approach to understanding dated dune stratigraphies. Earth Surf. Process. Landforms, 39: 614–631. doi: 10.1002/esp.3471
Current work is focused on applying the methods described in this paper to large empirical datasets, in an attempt to obtain more meaningful information on past climate forcing conditions than has previously been possible.
This work is being carried out in collaboration with Prof. Dave Thomas (University of Oxford).
The main findings were:
- thicker preserved sedimentary records reflect periods of more intense aeolian activity
- localized switching between erosion and deposition results in discontinuous and highly variable stratigraphic sequences
- a preservation bias towards younger deposits is observed, potentially leading to a continuum of accumulation that decays approximately in proportion to 1⁄√age
- time periods not represented by deposition can in some cases be interpreted as periods of higher precipitation and/or lower wind energy
- an asymmetry exists between the efficiency with which past ‘drier’ and ‘wetter’ episodes can be identified, which relates to the time-separation of depositional periods and the correct distinction between hiatuses due to forcing conditions and those due to under-sampling
- random dating errors (statistical uncertainty), increasingly which age, filter-out higher frequency events from the record
A new data treatment method (termed Accumulation Rate Variability) was developed which provides an efficient proxy for accumulation rates, and therefore the intensity of aeolian activity, with significant improvements over existing date-frequency methods.
This work was published in the following paper, which contains a full description of the model and discussion of findings:
Bailey, R. M. and Thomas, D. S. G. (2014), A quantitative approach to understanding dated dune stratigraphies. Earth Surf. Process. Landforms, 39: 614–631. doi: 10.1002/esp.3471
Current work is focused on applying the methods described in this paper to large empirical datasets, in an attempt to obtain more meaningful information on past climate forcing conditions than has previously been possible.
This work is being carried out in collaboration with Prof. Dave Thomas (University of Oxford).
Novel palaeoenvironmental archives in southern Africa: sand ramps
Landforms known as 'sand ramps' are being sampled in southern Africa in an attempt to access a previously under-used archive of environmental change. This work is the DPhil project of Ms. Alex Rowell. Field and laboratory work are currently underway, and further results will be described here, and published, as they become available.
Collaborators on this project:
Prof. Dave Thomas (University of Oxford).
Ms. Alex Rowell (DPhil student)
Photos below show (left to right) sand ramp deposits, sampling equipment, landscape context (southern Namibia).
Landforms known as 'sand ramps' are being sampled in southern Africa in an attempt to access a previously under-used archive of environmental change. This work is the DPhil project of Ms. Alex Rowell. Field and laboratory work are currently underway, and further results will be described here, and published, as they become available.
Collaborators on this project:
Prof. Dave Thomas (University of Oxford).
Ms. Alex Rowell (DPhil student)
Photos below show (left to right) sand ramp deposits, sampling equipment, landscape context (southern Namibia).
Faunal dispersal, extinction and palaeoenvironmental change in Southeast Asia
This project will provide new information on the timing of faunal dispersals in southern China and Southeast Asia over the last 300,000 yrs, during periods of widespread paleoenvironmental change. For example, the expansion of the rainforests in this region brought about by the variable climatic conditions enticed fauna (and humans) into this region, causing faunal turnovers, extinctions and creating new faunal assemblages. The timing of these events is largely unknown and the timing of these dispersals, according to the Southeast Asian evidence, is much younger than the equivalent Chinese and Australian chronologies.
This work is led by Dr Kira Westerway (MacQuarie University, Sidney, Australia).
This project will provide new information on the timing of faunal dispersals in southern China and Southeast Asia over the last 300,000 yrs, during periods of widespread paleoenvironmental change. For example, the expansion of the rainforests in this region brought about by the variable climatic conditions enticed fauna (and humans) into this region, causing faunal turnovers, extinctions and creating new faunal assemblages. The timing of these events is largely unknown and the timing of these dispersals, according to the Southeast Asian evidence, is much younger than the equivalent Chinese and Australian chronologies.
This work is led by Dr Kira Westerway (MacQuarie University, Sidney, Australia).
