Research Report Man and Biosphere Young Scientist Award. Abstract

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1 Research Report Man and Biosphere Young Scientist Award By Juan Carlos Silva Tamayo Assistant Professor, Universidad de Caldas Marie Curie Fellow, Stanford University Abstract Stalagmites and organic rich sediments from high altitude continental watersheds have been collected and dated to determine their potential as climate variability and high altitude biodiversity archives. Ages spanning from 16 Ky to the present have been determined using U- Th dating in selected stalagmite records from the Andean Mountain Belt (Cinturon Andino) in northeastern Colombia. AMS 14 C dates from 4.4 Ky to the present have been in turn obtained in continuous sediment cores from a watershed in the most northern- central part of the Cinturon Andino. The obtained ages allowed selecting these records for further research in climate variability and biodiversity during the late Holocene at the Tropical Cinturon Andino.

2 1. Introduction The 20 th century witnessed an exponential increase in anthropogenic CO2 emissions to the atmosphere. Investigating the possible effects of anthropogenic (industrial) CO2 emissions on global climate has become a priority to the international community. Intensive research has been done in order to constrain the effects of global warming on the marine and continental ecosystems and on the water resources. However the real effects (magnitude and timing) of anthropogenic CO2 emissions and global climate warming have remained controversial due to the discrepancies of the short term - instrumental data (restricted to a few decades). Moreover, the lack of continuous and reliable instrumental data at equatorial latitudes hampers our understanding of the effects of anthropogenic CO2 emissions and global climate variability on the equatorial continental and marine ecosystems and water resources. This research aims on investigating the real effects of changing atmospheric pco2 and global climate variability on the equatorial high altitude (Andean) continental ecosystems and on the northern South American Pre- Hispanic Cultures. High- resolution oxygen isotopes in speleothems, especially stalagmites, have been recently successfully used to investigate regional and global climate variability. Several speleothem sites were visited along the Andean Mountain Belt (Cinturon Andino) to collect stalagmite that can provide continuous high- resolution records of Climate variability along this UNESCO biosphere reserve. Funding from the MAB have been used to support this research. Specifically, Funding have been used to help performing the geochronology of these climate archives.

3 Here we report precise U- Th dating of several stalagmites from one site (the Penon cave) at the northeastern most part of the Cinturon Andino. Results suggest stalagmite record of climate variability extending back t 16 Ky. High altitude mountain watersheds and lake are, on the other hand, alternative archives of climate variability and also mountain floral biodiversity. One sediment core was collected on a watershed from at the central north- western Andes. This watershed is located at the Sub Paramo- Paramo boundary right below where the tree line is located (ca 4200 masl). Funding from the MAB program also helped dating this core. Late Holocene ages have been obtained for this core. These ages may provide important information about the changes on floristic biodiversity during the late Holocene that can be compared with the high- resolution stalagmite record of climate variability. 2. Location of the studied areas Several speleothem sites have been visited along the Cinturon Andino and the Caribbean Region (i.e. Colombia and Panama, Fig. 1). These sites contain potential stalagmite growths that can be potentially used for climate variability studies. These sites also present variable lithologies which span from the early- middle Paleozoic, up to the Miocene. Watershed cores have been collected at the Triunfo watershed of the amortisation area of the Colombian Snow Peaks Natural National Park. The study area is located at the Central Cordillera of Colombia. This area is characterized by a continuous volcanic activity (Fig. 1). 3. Results Initial stratigraphic analysis of ca 30 stalagmites allowed selecting the best- preserved and likely more continuous records for high resolution U- Th dating. From all the visited sites (7 in total, Fig. 1) only 2 (The Penon Area) provided stalagmites

4 with no obvious stratigraphic discontinuities (Fig. 2). The visited sites at the la Guajira, Toluviejo, Los Guacharos National Park and the San Luis Park in Colombia and the Maje Area in Panama did not provide stalagmite records with continuous stratigraphies. More importantly, in these sites, the stalagmites usually display high detritus contents, which, due to their high Th contents, can hamper the U- Th dating Figure. 1. Location of the study areas. 1 Toluviejo (60 masl), 2. Alta Guajira (30 masl), 3. Rio Claro (600 masl), 4. Maje (10 masl), 5 El Penon and Indio Caves (2000 masl), 6. Guacharos (2300 masl), 7. Triunfo watershed (National Snow Peaks Park). White squares are caves. Gray squares are lakes.

5 Figure. 2. View of the El Penon Cave and some examples of the dated stalagmites. Note the high resolution record offered by the annual growth rings of the stalagmite records.

6 The stalagmite records yield U- Th ages that extend back to 16 Ky (Fig. 3). One of the stalagmites presents an stratigraphic record that even extend farther back to what can be determined by using the U- Th technique. The core analysed from the Triunfo watershed provided a continuous age sedimentation record since 4.4 ky (Fig. 4). This 6 m core shows no evident signs of stratigraphic discontinuities, but the presence of some intervals with volcanic ashes accumulations may suggest a lack of record of biologic material, i.e. polen, that can be used for reconstructing biodiversity changes along the high altitude Cadena Andina. However almost 80% of the core corresponds to well preserved fine- grained, organic rich material that can be used for this purposes. CAR 7 CAR 3 CAR 2 CAR Tempo (anos A.P.) Years before the present Figure. 3. U/Th Ages of the analyzed stalagmites at the El Penol cave. Notice how the different dated stalagmites show a continuous Holocene record. Se also figure 2 for quality of the stalagmite records.

7 Figure. 4. AMS 14 C ages of one single sediment core in a watershed at the Snow peaks National Park of Colombia. Northern Andean Mountain Belt ( Cinturon Andino). See Fig. 1 for location.

8 4. Conclusions. Speleological visits to seven speleothem sites in northern South America and Panama allowed identifying excellent stalagmite records for climate variability studies. Thus far, only one site (El Penon), provided satisfactory stalagmite records that can be used for these purposes. Precise high resolution U- Th dating of the stalagmite records at this site yield ages that span the whole Holocene and even to the late Pleistocene. The age of one stalagmite can extend more back in time. AMS 14 C dating of a sediment core from a watershed at the northern- Central Colombian Andes provided late Holocene ages. The combined stalagmite and watershed archives allow predicting continuous records of climate variability and biodiversity in the northern most part of the Tropical Cinturon Andino. 5. Future research, outreach and prespectives. The ages obtained and the characteristics of the studied geologic records suggest that these are good archives for climate variability and biodiversity during the Holocene at the equatorial Neotropics, specially along the Cadena Andina. Multi- proxies analyses are currently being done in the watershed cores, i.e. sedimentology, palynology, geochemistry, in the high altitude water located along the Central and Western Cordillera of Colombia (Fig. 1). Further dating of three more cores will be performed. A master student is currently doing this work at the Geosciences Department of the Caldas University, Manizales, Colombia. This work will allow correlating main Holocene changes in regional climate and rain regime to major modifications of the equatorial high altitude ecosystems. C and O isotope analyses are currently being done in the Late Holocene well- dated stalagmites from the El Penon site in north- eastern Colombia (Fig. 1). This work is currently being perform by a Colombia (geologist- anthropologist) master student at the Geoscience Department of the Sao Paulo University, Sao Paulo, Brazil. Besides determining climate variability, this student is also currently determining how important changes on the Colombian pre- Hispanic pottery styles, which seem to

9 have paralleled main cultural changes that occurred around the 9 th century A.D. are related to major changes in regional tropical climate. This research ultimately aims on contributing to have a better understanding of the possible future effects (timing and magnitude) of climate variability and water resources crises on the human population around the equator. One Brasilian PhD student is concentrated on the long term (Pleistocene to recent) record of climate variability based on the well- dated stalagmites from the El Penon site. This research will provide important information of the longterm vs shortem climate variability in the Neotropical Cadena Andina. Thus far, one manuscript is being written focused the U- Th dating of the speleothems. We expect to have other two manuscripts written by the end 2013 on both, the short and the long- term climate variability along the Neotropical Andean Chain. Finally, the University of Caldas has recently funded Dr Juan Carlos Silva Tamayo to continue the research at the high altitude watersheds of Central Colombia. The funding granted to Dr Silva- Tamayo will ensure the continuation of his work in this area, which was partially funded by the MAB award.