Evolution of the Monsoon Biosphere and Mountain Building in Cenozoic Asia
About the Conference
The Asian monsoon is the type example of a climatic system intimately linked with the tectonic evolution of the solid Earth, yet to date demonstrating these proposed links has been difficult because of a lack of detailed climatic and erosional records that span tectonic timescales, equal to those over which the Himalayas and Tibet have developed. A campaign of scientific drilling of sediments from the marginal seas of eastern Asia and the Indian Ocean conducted by the International Ocean Discovery Program (IODP) in 2014–2016 has now partly solved this problem, with a number of deep drill sites in key areas of the East Asian, Indian and Australian monsoon subsystems now providing long duration records of erosion, weathering and environment. Scientific results from each expedition are now emerging, yet any attempt to understand the monsoon as a whole needs to integrate results from across the regions in order to assess links between monsoonal subsystems, as well as to compare oceanographic records with erosional records and continental environmental data. The marine data moreover must be reconciled with information from onshore concerning the evolving tectonics of the ranges and the height of the Tibetan Plateau, all of which need to be integrated with our understanding of modern monsoon atmospheric dynamics.This Chapman Conference aims to bring together these different communities to discuss how the new drilling results relate to observations made onshore and to what extent they validate existing reconstructions of monsoon development. The emphasis will be on million-year, tectonic timescales, although millennial scale records will also be welcome. IODP has provided the largest source of new data concerning this interdisciplinary field in several decades. We now seek the chance to try to integrate the results into a new understanding of the Asian monsoon and to resolve which questions are still outstanding. We solicit contributions on the following themes.
This session provides the intellectual background for the rest of the meeting by summarizing the nature of land-ocean-atmospheric coupling that powers the modern monsoon. We aim to present the nature of and controls on modern precipitation and wind patterns and discussion how they might have differed in the geologic past, especially prior to the establishment of high topography.
This session will focus on well-dated records of evolving oceanic currents and biogenic productivity in relation to the intensity of the Asian monsoon winds. We especially want to constrain times of transition, strengthening, or weakening, as well as examining evidence for the initial onset.
In this session we focus on evidence for the evolving climatic conditions in the Asian continental interior, drawing on appropriate proxies from the marine cores as well as sedimentary records preserved in continental basins. This will include both reconstruction of vegetation, as well as changing intensities of continental weathering and aridity. Again, we focus on identifying the time of initial onset and times when monsoon intensity changes.
Records of Continental Erosion
This session will focus on reconstruction of changing rates and patterns of erosion in the mountainous source areas in South and Southeast Asia and potential relation with fan sedimentation to determine their response to the evolving climates in Cenozoic Asia.
Modeling and Links to Continental Tectonics
Here we examine whether there are links between the evolution of the monsoon, the history of erosion and the tectonic development of the mountains especially in South Asia in order to understand the degree of coupling and the potential for feedbacks.
The primary scientific hypotheses to be addressed by meeting are:
- Intensification of summer monsoon rainfall and/or winter wind strength correlates with stronger oceanic productivity and faster erosion of continental source areas.
- Periods of strong chemical weathering correlate with times of vegetation change from C4 to C3 plants, lower salinities in the ocean, intensified oceanic upwelling and faster clastic sediment delivery
- Phases of rapid erosion and clastic sedimentation in the oceans match times of structural reorganization in the Himalaya, such as motion on major faults.
- Changes in paleo-altitude proxies and drainage reorganization events onshore precede or correlate with times of climatic and oceanic change.
- Times of stronger chemical weathering, oceanic upwelling and clastic erosion correlate with phases of enhanced carbon burial in submarine fans and/or with times of global cooling