Conference program and abstracts - Coastal-Change.Org

Millennial-scale records of North American Monsoon
during the last glacial period from Mexican Deserts
Priyadarsi Roy 1 , Jesus David Quiroz 2 , Marcela Charles 2 , Nayeli Lopez 3 ,
Francisco Romero 1 and M.P. Jonathan 4 *
1
Instituto de Geologia, Universidad Nacional Autónoma de México, CP
04510, México DF, México
2
Posgrado en Ciencias de la Tierra, Universidad Nacional Autónoma de
México, CP 04510, México DF, México
3
USAI, Facultad de Quimica, Universidad Nacional Autónoma de México,
CP 04510, México DF, México
4
Centro Interdisciplinario de Investigaciones y Estudios sobre Medio
Ambiente y Desarrollo (CIIEMAD), Instituto Politécnico Nacional (IPN),
Calle 30 de Junio de 1520, Barrio la Laguna Ticomán
C.P. 07340, Del. Gustavo A. Madero, México, D.F., México.
*Corresponding author: mpjonathan7@gmail.com
ABSTRACT
The Sonora and Chihuahua Deserts are spread over at least 8 different
states present in the north-western and northern Mexico. The North
American Monsoon (NAM) or Mexican Monsoon refers to the system that
brings summer precipitation to this arid/ semi-arid part of Mexico and
southwestern USA. It contributes ca. 70-80% of total annual precipitation
along the western slopes of the Sierra Madre Occidental (northern
Mexico) and ca. 40-50% of total precipitation in Arizona and New Mexico
(southwest USA). The multi-proxy data from lacustrine deposits located
between 23° N and 31° N (paleolakes La Salada, Babicora and San
Felipe) provide spatio-temporal and millennial-scale paleohydrological
records over the last glacial period related to the dynamics of summer
precipitation as well as westerly winter storms. The inverse relationship
between the proxy records of runoff into lacustrine basins of northern
Mexico and winter precipitation over the southwestern USA indicate the
westerly winter storms had minimal influence south of 30°N and the
paleohydrological changes are mainly summer precipitation controlled.
The runoff records between 20 and 60 cal. kyr BP show a first order positive
relationship with the summer insolation. On millennial-scale, the basins
received more than average runoff during the warm interstadials and
vice versa. During the cold stadials, the westerly winds transported
minimally chemically altered sediments from the dry watershed. Highresolution
geochemical proxies suggest lower than average runoff and
higher than average lake water salinity during the Younger Dryas and
Heinrich events 1, 2 and 3. However the uncertainties associated with 14 C
based age model, hiatus in sedimentation and extrapolation of the age
model for the lower part of core could be the reason behind the lack of
above mentioned observations during rest of the Heinrich events.
The Fourth IGCP 588: PREPARING FOR COASTAL CHANGE 13