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Scientists prepare to study Amazon's “time capsules”
Samples collected from the forest's subsoil hold precious clues about the biome's past
More than two thousand plastic tubes containing samples from deep subsoil in the Amazon are due to be sent in the coming weeks from USP’s Geosciences Institute (IGc) to a laboratory at the University of Minnesota in the United States, as part of a major international effort to uncover the remote past of the planet’s largest rainforest.
The cylindrical samples, known as “cores”, come from a drilling performed between may and september 2024 on the southern shore of Marajó Island (municipality of Bagre, Pará), which reached a depth of 924 meters. Each tube corresponds to a segment of the borehole, filled with sediments that were deposited there by the Amazon River in the distant past and have now been recovered by the efforts of the Trans-Amazon Drilling Project (TADP), an international initiative involving scientists from 12 countries.
The deeper the sediment, the older it is. Researchers estimate that the 924 meters drilled correspond to approximately 25 million years of Amazonian history. The drilling spot has a strategic advantage: as it is located near the mouth of the Amazon River, it concentrates sediments that have been carried by the river’s tributaries throughout the entire Amazon Basin, providing insight into how the biome’s climate, landscape, and biodiversity have evolved over this period.
Click to watch the video report on the TADP project, produced by Jornal da USP. Also available on USP’s YouTube Channel
“These changes in the environment and climate are recorded in the sediments that accumulate in the sedimentary basins,” geologist André Sawakuchi, a professor at IGc-USP and coordinator of TADP in Brazil, says. These sediments are primarily composed of debris from plants, animals, soils, and rocks that were transported by water and subsequently deposited on the beds of rivers and lakes in the past. “Over time, this debris turns into sedimentary rocks. So if we can access the sedimentary rocks, we’re accessing an archive of the planet’s past,” Sawakuchi explained to Jornal da USP.
Essentially, it’s as if each of these cores were a time capsule, containing the “remains” of everything that existed on the Amazon’s surface at the time those sediments were generated. With this material in hand, it is possible to extract a range of information about the biome’s climate, landscape and biodiversity at that particular time. Traces of pollen, for example, enable us to infer the type of vegetation cover in the forest, while traces of coal serve as an indicator of the frequency of wildfires and the prevailing climate at the time.
Research Lines
Once the bureaucratic issues have been resolved, the material will be flown to a specialized repository at the University of Minnesota, where the cores from a previous drilling project conducted by TADP between June and December 2023 in Acre (Rodrigues Alves municipality) are already deposited. In that case, drilling reached a depth of 923 meters (by comparison, the peak of Corcovado in Rio de Janeiro is 710 meters high).
The next step will be to open the cores and collect smaller samples, which will be distributed among the project’s various experts for physical, chemical, and biological analyses of the material. These analyses will help uncover the answers the project is looking for.
The first drillings in Acre happened in August 2024, and the samples are already being analyzed in various laboratories associated with the project. Approximately 60 researchers from various specialties are participating in the initiative across the involved countries. In Brazil, in addition to USP, as the institutional representative, scientists from ten other public universities (Unicamp, Unifesp, UFF, Uerj, Ufac, Ufam, UFSE, UFMT, UFPA, UnB) and the Museu Paraense Emílio Goeldi are participating.
At IGc, Sawakuchi is responsible for producing some of the most fundamental information in the entire process: the age and geographical origin of the samples. This is achieved through a series of procedures and analyses of the quartz grains present in the sediment sand, allowing us to determine when they were last exposed to light and from which macro-region of the Amazon Basin they originated.
Part of this work needs to be done in a dark laboratory to measure the degree of luminescence of quartz when exposed to different types of radiation and temperatures. “The quartz grains produced in the soils of the Andes have a low luminescence compared to the quartz produced in the flatter soils of Central Brazil or the Guiana Shield, for example. So we can differentiate effectively (where that sand came from),” explains Sawakuchi.
Information on the age and geographical origin of sediments is significant for mapping the Amazon Basin’s river network as it looked in ancient times. This is another line of research associated with the project: understanding how large-scale geological events (such as the uplift of the Andes) have shaped river drainage patterns and other fundamental characteristics of Amazonian geography – which, in turn, have a significant influence on the evolutionary processes and climate systems that have shaped the biome into its current configuration.
The evidence available so far suggests that the Amazon River, as we know it today (by draining eastwards into the Atlantic Ocean), began to form around 11 million years ago, according to geologist Cleverson Silva, a professor at the Fluminense Federal University (UFF) and a member of the TADP executive committee. “This would have a direct association with an increase in the uplift rates of the Andes,” Silva explained to Jornal da USP.
The chronological mapping of the presence of Andean-origin sediments in the cores collected by the project should therefore help refine research into how and when these processes occurred. “That’s a point I’d like to determine more precisely,” Silva adds.
The luminescence techniques used in Sawakuchi’s laboratory are ideal for dating more recent samples, up to 500,000 years old. Older samples require different dating techniques, based on isotopes and microfossils.
3D model of the well and drilling procedures for the TADP project – Illustration: GeoHereditas
Depth
The similarity between the depths reached in the two drillings (923 and 924 meters) was a mere coincidence, according to the researchers. The original target was to drill up to 2,000 meters deep in Acre and 1,200 meters deep on Marajó Island, which would have enabled us to go back up to 65 million years in the history of the forest. However, technical difficulties and budget limitations prevented the team from achieving these goals. The fact that the sediments were in a poorly consolidated state (and not rigid, like rock) made the work very hard, causing the drilling rig to get stuck several times and requiring a series of procedures to be performed to prevent the well walls from collapsing.
Drilling continued until it was no longer feasible due to limited time and resources, as well as team exhaustion. In total, there were more than 280 days of fieldwork: six months in Acre and three and a half months on the Marajó Island. Operations ran 24/7, with two teams of technicians and researchers taking turns in 12-hour shifts, facing the heat, humidity, and all the logistical difficulties of working in the Amazon.
“It was intense; from the planning to the operation and implementation of the work, it was intense,” researcher Isaac Bezerra, a post-doctoral student at IGc and TADP’s manager, summarizes. He spent 220 days in the field, coordinating the work at the two drilling sites. “But at the end of the day, the feeling is of success, given the effort we made and the material we recovered.”
Although they didn’t reach the desired depths, they were the deepest scientific holes ever drilled in the Amazon. “We’re very relieved and happy with what we’ve achieved,” researcher Sherilyn Fritz, from the University of Nebraska in the United States, who is also on the project’s executive committee, told Jornal da USP. “We’ve achieved more than any other (research) group in terms of getting these long continuous records, from various places in the Amazon Basin; so they’re unprecedented records. We don’t know what stories they will tell yet, of course. Still, we are optimistic that this will lead to some great leaps in knowledge, which will be revolutionary in terms of understanding Amazon’s history and how it became the magnificent ecosystem it is today.”
The initial goal, when TADP was conceived around ten years ago, was to drill at five locations. However, delays and budgetary complications triggered by the COVID-19 pandemic ultimately forced researchers to select just two drilling sites – one at each “tip” of the Amazon Basin. The start of drilling in Acre in June 2023 was first reported by Jornal da USP.
The cost of the drilling was US$ 4 million, funded by the International Continental Scientific Drilling Program (ICDP), based in Germany, in partnership with the National Science Foundation (NSF) from the United States, the Smithsonian Tropical Research Institute based in Panama, and the São Paulo Research Foundation (Fapesp) in Brazil. The company responsible for the drilling was Geosol, from Minas Gerais.
In addition to Brazil and the United States, the project includes researchers from Panama, Germany, the Netherlands, Sweden, France, Austria, Iceland, Denmark, Canada, Italy, and Switzerland.
More information: andreos@usp.br; with André Sawakuchi, from IGc USP
English version: Nexus Traduções, edited by Denis Pacheco
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A reprodução de matérias e fotografias é livre mediante a citação do Jornal da USP e do autor. No caso dos arquivos de áudio, deverão constar dos créditos a Rádio USP e, em sendo explicitados, os autores. Para uso de arquivos de vídeo, esses créditos deverão mencionar a TV USP e, caso estejam explicitados, os autores. Fotos devem ser creditadas como USP Imagens e o nome do fotógrafo.
A reprodução de matérias e fotografias é livre mediante a citação do Jornal da USP e do autor. No caso dos arquivos de áudio, deverão constar dos créditos a Rádio USP e, em sendo explicitados, os autores. Para uso de arquivos de vídeo, esses créditos deverão mencionar a TV USP e, caso estejam explicitados, os autores. Fotos devem ser creditadas como USP Imagens e o nome do fotógrafo.