Palaeoenvironmental record of the last 70 000 yr in San Felipe Basin, Sonora desert, Mexico: preliminary results

Abstract

Con el propósito de documentar los cambios paleoambientales, se lleva a cabo una investigación multidisciplinaria en la Laguna Seca de San Felipe, Baja California. Los resultados preliminares incluyen análisis sedimentológicos de diatomeas y propiedades magnéticas de un núcleo de 9.5 m de longitud. Fechamientos de 14C sugieren que la secuencia abarca los últimos 70 000 años. Los resultados de propiedades magnéticas (χ, χfd%, MRIS, MRA, parámetros de histéresis y cocientes S), contenido de materia orgánica y tamaño de partículas indican condiciones contrastantes entre el último glacial del Pleistoceno y el glacial tardío-Holoceno. Se infieren condiciones secas entre 70 000 y 45 000 años A.P. El pleniglacial, entre 34 000 y 19 000 años A.P., está caracterizado por condiciones húmedas. A partir de 12 000 años A.P. la tasa de sedimentación y los parámetros magnéticos se incrementan en un factor de 5, cambio interpretado como el aumento en el escurrimiento de aguas superficiales. Entre 7000 y 6000 años A.P. se registra un periodo de aridez, a partir del cual se recuperan las condiciones húmedas. El establecimiento de las actuales condiciones áridas se infiere alrededor de 4000 años A.P.

A 14‐ka Record of Dust Input and Phytoplankton Regime Changes in the Subtropical NE Pacific: Oceanic and Terrestrial Processes Linked by Teleconnections at Suborbital Scales

“…(ii) During the early Holocene interval between ~11 and 7 ka, the region showed an increase in winter precipitation relative to the previous period with punctuated episodes of alluvial fan deposition (at ~ 10.5, 9.5, 9, and 8 ka; Antinao et al, ; Arriaga‐Ramírez & Cavazos, ), with overall wetter condition than today for most of the Sonora desert (Ortega‐Rosas et al, ; Roy et al, , ). (iii) The middle‐ to late‐Holocene over the last 7 ka shows the interruption of alluvial fan aggradations matching with desiccation of all lakes and the progressive drying of the BCP (Antinao et al, ; Arriaga‐Ramírez & Cavazos, ; Ortega et al, ; Ortega‐Rosas et al, ; Roy et al, , , ).…”

“…In fact, most of the reconstructions reveal that during the end of the Late Pleistocene and the Holocene, three main periods summarize the climate on land (Antinao et al, ), coincident to changes in insolation and ITCZ migration (Figure ). (i) During the deglaciation, between 14 and 11 ka, the region experienced discrete episodes of effective moisture during summer (at ~13, 12, and 11 ka) identified by discrete highstands of lake levels (Ortega et al, ), vegetation changes in the BCP (Rhode, ), alluvial fan deposits, and aggradation activity (Antinao et al, ; Spelz et al, ). (ii) During the early Holocene interval between ~11 and 7 ka, the region showed an increase in winter precipitation relative to the previous period with punctuated episodes of alluvial fan deposition (at ~ 10.5, 9.5, 9, and 8 ka; Antinao et al, ; Arriaga‐Ramírez & Cavazos, ), with overall wetter condition than today for most of the Sonora desert (Ortega‐Rosas et al, ; Roy et al, , ).…”

“…and 11 ka) identified by discrete highstands of lake levels (Ortega et al, 1999), vegetation changes in the BCP (Rhode, 2002), alluvial fan deposits, and aggradation activity (Antinao et al, 2016;Spelz et al, 2008). (ii) During the early Holocene interval between ~11 and 7 ka, the region showed an increase in winter precipitation relative to the previous period with punctuated episodes of alluvial fan deposition (at ~10.5, 9.5, 9, and 8 ka; Antinao et al, 2016;Arriaga-Ramírez & Cavazos, 2010), with overall wetter condition than today for most of the Sonora desert (Ortega-Rosas et al, 2008;Roy et al, 2013Roy et al, , 2015.…”

Lateglacial and Holocene palaeoenvironments at Sierra La Madera, northwestern Mexico: Sharp signals of Younger Dryas and North American monsoon

“…The establishment of the tropical thorn scrub in TB since the mid‐Northgrippian also suggests that winter temperatures were generally above freezing, as inferred by the low tolerance of tropical taxa to cold temperatures. In a more regional context, a shift to greater aridity at 7000 cal a bp was also recorded at Laguna Seca San Felipe, Baja California (Ortega Guerrero et al ., 1999), which persisted until approximately 6000 cal a bp.…”