Proposal Response Letter - iodp.tamu.eduiodp.tamu.edu/scienceops/precruise/amazon/859-PRL_Baker_FOR_WEB.pdf · Proponents Response Letter: Amazon 859-Full2 Proponents: Paul A. Baker,

Proposal Response Letter

Proposal: 859-Full2 Short Title: Amazon Margin Drilling Lead Proponent: Paul Baker Submission Date: March 22, 2018

Proponents Response Letter: Amazon 859-Full2

Proponents: Paul A. Baker, Cleverson Silva G., Sherilyn C. Fritz, Tadeu Reis

22 March 2018

(1) Responses to SEP comments and requests for revisions of the Site Survey Data

1) SEP - The target depths for Sites 5A and 13A are incorrectly drawn on the Site form figures

(drawn to Paleocene, text indicates Eocene target).

ANSWER: New figures were drawn with the correct target depths and uploaded on SSDB.

2) SEP - Site form has incorrect SP location for Site 12A on Inline 0047-0021. Text indicates

SP235, while the crossline 0053-0738 appears to cross near SP958.

ANSWER: The site form table and figure were corrected. The right shot point on inline 0047-

0021 is SP 958. The new figure was uploaded on SSDB.

3) SEP - Watchdogs could not locate a segy file for Line 0239-0067 (Sites 7A and 10A) in the

SSDB.

ANSWER: Line 0239-0067 was loaded on SSDB with a different name. On SSDB we used its

full original name S0.M.B051.P0168.E0239.L0067.MTVFL.1997.01.

4) SEP - There was extended discussion amongst the WDs and the panel concerning criteria for

choosing sites and site prioritization during drilling. We suggest that the proponents carefully

prioritize the alternative sites. For example, it seems that Sites 5A or 8A may be the best

alternative for characterizing the upper section that is the goal of Site 3B. Given the deep target

depths for each site, the WDs suggest that 11A be re-categorized as an alternate site due to the

presence of a chaotic interval in the upper section and that 3B and 7A remain primary sites, with

multiple holes at each site (see Section III). Site 9A penetrates an extensive transparent feature in

the upper section; WDs are concerned about drilling through an MTD or, at the least, very

chaotic facies will compromise the site.

ANSWER: We accepted SEP's suggestion and re-categorized site AM-11A to an alternate site.

We also eliminated site AM-9A, following SEP's advice. The following table shows the

respective prioritization for primary sites AM-3B and AM-7A and their alternates.

The main criteria for prioritizing the sites are completeness of the drilling section and water

depth, since the proposed sites are on the upper continental slope, close to the upper limit forsafe

and efficient operational conditions, ca. 300 m water depth.

Also, at the EPSP meeting, Ken Miller requested that we provide a table of sites and alternate

sites (included below), explaining what scientific objectives would be met or sacrificed given

hypothetical scenarios regarding core recovery and total depth penetration. We limited our

discussion in the table to the two primary sites, as the alternate sites would have the same

outcomes, with somewhat different interval depths.

Primary Alternates

AM-3B

AM-8A (1st)

AM-13A (2nd)

AM-5A (3rd)

AM-6A (4th)

AM-7A

AM-11A (1st)

AM-12A (2nd)

AM-10A (3rd)

AM-4B (4th)

Primary site AM3-B (and its alternates) has as its main goals:(1) recovery of the thickest and

most continuous Quaternary section and (2) recovery of the sedimentary sectionfrom basal

Quaternary to the Eocene (38 Ma). The site is located in 441 m water depth and the target depth

is 1631 mbsf. The alternate sitesfor AM-3B are, in order of priority, (1) Site AM-8A, located in

291 m water depth with a very continuous sequence above the 1.98 Ma horizon, a reasonably

thick (~76 m) unit from 1.98 to 8 Ma, and the target depth at 1605 mbsf; (2) Site AM-13A,

located in 312 m water depth, has minor unconformities in the Quaternary section above the 1.98

Ma horizon, but has a thick interval from the 1.9 to the 8 Ma horizon (111 m), a well preserved

section from 8 Ma to the 38 Ma horizon, and the target depth is the shallowest at 1519 mbsf; (3)

Site AM-5A is located in shallow water (205 m), perhaps too shallow, it has some

unconformities above the 1.98 Ma horizon, an expanded section (150 m) between 1.98 and 8 Ma,

and the target depth is at 1591 mbsf; (4) Site AM-6A, located in 383 m water depth, has some

unconformities and a disturbed interval (MTD) above the 1.98 Ma horizon, the thickness of the

1.98 to 8 Ma interval is small (60 m), and the target depth is at 1,705 m.

Primary Site AM-7A(and its alternates) has as its main goal the recovery of the oldest possible

sediments. Here, the target depth is the top of the Paleocene Limoeiro Formation at 2203 mbsf.

The site is located on the uppermost continental slope in 373 m water depth. This site has an

expanded sequence (190 m) between 1.93-8 Ma relative to site AM-3B, as well as a moderately

thick (543 m) late-Miocene to late-Eocene (8-38 Ma) section. The pairing of sites AM-3B with

AM-7A will enable recovery of a nearly complete Cenozoic sequence with good stratigraphic

continuity and high resolution in most intervals. The alternates for site AM-7A, in order of

priority, are: (1) Site AM-11Alocated in 289 m water depth, and the target depth at 1995 m,

nearly 200 m shallower than primary site AM-7A, with an undisturbedPaleogene and lower

Neogene sequence; (2) Site AM-12A is located in 291 m water depth, and a target depth at 2213

mbsf, with a reasonably thick and undisturbed Miocene to Paleocene section; (3) site AM-10A is

located in 475 m water depthand has a target depth of 2236 mbsf. The Quaternary sequence has

some minor unconformities; the 1.98 to 8 Ma interval is thin (54 m); (4) Site AM-4B is located

in 227 m water depth and the target depth is 2176 mbsf. Here, the upper Quaternary sequence

contains unconformities and buried channels.

SEP stated that check shots or VSPs should be added to our logging plan as these would help to

tie boreholes to our seismic profiles.

Answer: We will include check shots and zero offset VSP in our logging plan. We presented

the revised logging plan at the EPSP panel meeting last February.

SEP also recommended that we continue to develop the coring and logging operations plan

working with JRSO.

Answer: We have been in frequent contact with JRSO (Mitch Malone) and we discussed our

coring and logging operational plan during the last EPSP meeting. Further, we just submittedto

EPSP the operational reports from industrial wells available in the vicinity of the proposed sites.

At the time of submission of our final proposal, we were told that CAPES IODP-Brazil would

fund a short cruise to our field area in order to allow collection of additional piston cores and

multibeam survey data. Unfortunately, funding for that cruise did not materialize. However, in

the meantime the SEP review concluded that there was no necessity for collection of the cores.

EPSP requested a bathymetric chart of the region surrounding each drill site (perhaps 1 km

radius), but told us that our 3-d grid will suffice for producing such a chart, obviating the need

for a multi-beam survey.

Answer: CAPES is still trying to get funds from the industry and from the Brazilian Petroleum

Agency (ANP) for asite survey cruise. The bathymetry atall site locations is very gentle and our

3D seismic grids cover the entire area and havesufficient resolution to show the local

morphology around the site locations.

(2) Response to External Reviews

We received three external reviews that were solicited by SEP. In summary, the external

reviews were very positive. Here we address the few points in their reviews that seem to require

response.

Reviewer A (RA), had positive comments about the scientific objectives and likely outcomes,

but took issue with several of our hypotheses. Given the word limit of the PRL, at the suggestion

of Ken Miller, we created a table (below) that we believe adequately addresses RA.

RA was aware of some of our earlier work, but did not know about any of our marine

experience. Baker, Silva, and Reis, all have many years of oceanographic experience. Baker has

been a shipboard scientist on 4 DSDP/ODP expeditions, chief scientist on ten oceanographic

cruises (and countless limnologic cruises), chief scientist on two major terrestrial drilling

projects, and served multiple times as a panelist for DSDP and ODP. Silva and Reis have led or

participated in dozens of oceanographic cruises on US, German, French, Brazilian, and other

ships. They have both served on IODP panels. Their expertise is marine geology and

geophysics. They have many publications on the Amazon continental margin (among many

other study areas).

Reviewer B (RB) wrote that “it is importantto debate whether it is really possible to have an

understanding of Amazonian plant diversitybased only on pollen from the Amazon fan,

considering the size of the region.” As we described in our proposal, the IODP drilling that we

propose is only one part (a vital one) of the Trans-Amazon Drilling Project (TADP) that includes

5 continental sites, each of which will recover the Cenozoic sequence in its region, and together

will span most of the Amazon basin. ICDP has already funded part of the TADP and we expect

to receive the balance of the funding from a variety of other sources (government, private, and

industry). It is also important to reiterate that our proposed IODP drill sites are not on the

Amazon Fan, a region where continent-derived sedimentation is only active during sea level

lowstands and where sedimentation is highly discontinuous. These are some of the regions that

we selected drill sites on the upper continental slope away from the Fan.

RB also wrote that: “most questions that are under discussion inthe literature and are relevant

for other disciplines, as biodiversity analysis, are related to theNeogene and Quaternary. In this

context, site 11A would be the one that could be removedwith less impact for the general

importance of the results.” RB is correct in the first half of this statement, but the reason for that

is simply because there are no data from the Amazon basin prior to the Quaternary and late

Neogene (and very little data within this time span!), hence can be no literature on the topic.

Outcrops are extremely scarce; exploration drilling is represented by cuttings that are poorly

curated and very difficult to access; previous scientific drilling was limited to the last ca. 100 Ka.

We believe, as we set out in our proposal, that fundamental questions of earth and biotic history

can only be addressed by recovery of records from the remaining unknown 95% of the Cenozoic.

Reviewer C (RC) was positive throughout (e.g., “even if only half of the scientific objectives

would be achievedthe expedition would be a success but I think that most of the stated objectives

can beachieved with drilling at the proposed sites”), but asked about the possible feedback of the

Amazon on global climate. The latter is a provocative topic. As a major center for the global

Walker circulation, the Amazon has some ability to affect the global atmosphere. And as the

largest river on Earth with a modern total discharge ca. 0.2 Sverdrup (compared to 150 Sv of the

North Atlantic subtropical gyre or 15 Sv of AMOC), much of it entrained in the North Brazil

Current as the “surface-trapped” Amazon plume, the Amazon has notable local influence on the

circulation, chemistry, and (especially) biology of the western Equatorial Atlantic. Global

teleconnections are largely unknown, but conceivable (e.g., atmospheric methane concentration).

The new drill core records will provide the data that can be used to deepen our understanding of

possible Amazon-global feedbacks.

(3) References

Baker, P.A., Fritz, S.C., Dick, C.W., Eckert, A.J., Horton, B.K., Manzoni, S., Ribas, C.C.,

Garzione, C.N., Battisti, D.S., 2014. The emerging field of geogenomics: constraining geological

problems with genetic data. Earth Science Reviews 135, 38-47.

Bush, M.B., De Oliveira, P.E., Miller, M.C., Moreno, E., Colinvaux, P.A., 2004.

Amazonian paleoecological histories: one hill, 3 watersheds. Palaeogeography,

Palaeoclimatology, Palaeoecology, v. 214, p. 359-393.

D’Apolito, C., Absy, M., Latrubesse, E., 2013. The Hill of Six Lakes revisited: new data and re-

evaluation of a key Pleistocene Amazon site. Quaternary Science Reviews, v. 76, p. 140-155.

Dick, C.W., Lewis, S.L., Maslin, M., Bermingham, E., 2013. Neogene origins and implied

warmth tolerance of Amazon tree species. Ecology and Evolution, v. 3, p. 162-169.

Dowsett, H.J., et al., 2013. Sea surface temperature of the mid-Piacenzian ocean: a data-model

comparison. Scientific Reports, v. 3, p. 1-8.

Ford, H.L., Ravelo, A.C., Dekens, P.S., LaRiviere, J.P., Wara, M.W., 2015. The evolution of the

equatorial thermocline and the early Pliocene El Padre mean state. Geophysical Research Letters,

v. 42, p. 4878–4887.

Garreaud R.D., Molina A., Farias M., 2010. Andean uplift, ocean cooling and Atacama

hyperaridity: A climate modeling perspective. Earth and Planetary Science Letters, v. 292, p. 39-

50.

Garzione, C.N., McQuarrie, N., Perez, N.D., Ehlers, T.A., Beck, S.L., Kar, N., Eichelberger, N.,

Chapman, A.D., Ward, K.M., Ducea, M.N., Lease, R.O., Poulsen, C.J., Wagner, L.S., Saylor,

J.E., Zandt, G., Horton, B.K., 2017. Tectonic evolution of the Central Andean Plateau and

implications for the growth of plateaus. Annual Review of Earth and Planetary Sciences, v. 45, p.

529-559.

Haffer, J., 1969. Speciation in Amazonian forest birds. Science, v. 165, p. 131–137.

Held, I.M., Soden, B.J., 2006. Robust responses of the hydrological cycle to global warming.

Journal of Climate, v. 19, p. 5686-5699.

Hoorn, C., Bogotá-A, G.R., Romero-Baez, M., Lammertsma, E.I., Flantua, S.G.A., Dantas, E.L.,

Dino, R., Carmo, D.A., Chemale, F., 2017. The Amazon at sea: onset and stages of the Amazon

River from a marine record, with special reference to Neogene plant turnover in the drainage

basin. Global and Planetary Change, doi.org/10.1016/j.gloplacha.2017.02.005.

IPCC, 2013. Climate Change 2013: The Physical Science Basis. Contribution of Working Group

I to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change. Cambridge

University Press, Cambridge, United Kingdom and New York, NY, USA, 1535 pp.

Ribas, C.C., Aleixo, A., Nogueira, A.C.R., Miyaki, C.Y., Cracraft, J., 2012. Amazonia over the

past three million years. Proceedings of the Royal Society of London B 279, 681-689.

Silman M.R., 2011. Plant species diversity in Amazonian forests. In: Bush M., Flenley J.,

Gosling W. (eds) Tropical Rainforest Responses to Climatic Change. Springer Praxis Books.

Springer, Berlin, Heidelberg, pp. 269-294.

Stute, M., Forster, M., Frischkorn, H., Serejo, C.P., Broecker, W.S., 1995. Cooling of tropical

Brazil during the last glacial maximum. Science, v. 269, p. 379-383.

Takahashi, K., and D. S. Battisti, 2007. Processes controlling the mean tropical Pacific

precipitation pattern. Part I: The Andes and the eastern Pacific ITCZ. Journal of Climate, v. 20,

p. 3434–3451.

terSteege, H., et al., 2013. Hyperdominance in the Amazonian tree flora. Science 342, 1243092-

1243091-1243099.

Wang, X., Edwards, R.L., Auler, A. Cheng, H., Kong, X., Wang, Y., Cruz, F.W., Dorale, J.,

Chiang, H.-W., 2017. Hydroclimate changes across the Amazon lowlands over the past 45,000

years. Nature, v. 541, p. 204–207.

Zachos, J., Pagani, M., Sloan, L., Thomas, E., Billups, K., 2001. Trends, rhythms, and

aberrations in global climate 65 ma to present. Science, v. 292, p. 686-693.

Table 1. Statement of Hypotheses and their significances

Hypothesis number

Revised Statement of Hypothesis

Test Methods Scientific Significance of Hypothesis

Climate and Ocean Hypotheses H1a (i) and (ii)

(i) The Cenozoic SST history of the equatorial Atlantic mirrors the Zachos deep-sea δ18O record. (ii) The Cenozoic continental surface air temperature history of eastern tropical South America (TSA) mirrors the Zachos deep-sea δ18O record.

(i) Reconstruction of tropical SST record from alkenone, Uk37, δ18O, and Mg/Ca and comparison with the Zachos (2001) benthic isotopic curves. (ii) Reconstruction of TSA continental temperature from organic geochemistry and comparison with the Zachos (2001) curve.

Data-model offsets remain large for tropical SSTs (model SSTs too low) of the Cenozoic with implications for past CO2 levels and climate sensitivity (e.g., Dowsett et al., 2013). With singular exceptions (e.g., Stute et al. 1995), there are no determinations of past TSA continental air temperatures. We guess that the Cenozoic air temperature trend is similar to the tropical Atlantic SST trend (also poorly known) and similar to the Zachos curve, but with less change in the tropics than high latitude. The fate of tropical forests in global warming may depend on adaptation history of modern lineages to past climate (Dick et al. 2013).

H1b Thermal optima of the Cenozoic were wet periods. The (admittedly simplified) Held and Soden (2006) paradigm predicts a wetter Amazon in past (or future) thermal maxima and a drier Amazon in past cold periods.

Reconstruction of continental precipitation and Amazon runoff from organic geochemistry, pollen, and XRF elemental ratios and comparison with the Zachos curve, but also with known Quaternary climate forcings (summer insolation, E-W dipole, N-S Atlantic SST gradients) assumed to also operate in the pre-Quaternary.

The primary correlates of modern tropical forest diversity are precipitation amount and precipitation seasonality (Silman 2011). We expect that an ever-wet forest will be more diverse than a seasonally dry forest. But GCM simulations of tropical precipitation are not robust so paleo-precipitation observations are paramount.

H1c Increased precipitation and

Reconstruction of continental precipitation and Amazon runoff and comparison with

This will be a complicated hypothesis to test. The Humboldt current appears to have intensified in the

runoff in the Amazon coincide with cooling of the eastern equatorial Pacific (EEP) and enhanced Walker circulation.

history of EEP SST and Andean uplift (Garzione et al. 2016)

late Cenozoic (Ford et al. 2015), strengthening the Pacific E-W SST gradient and Niña-like conditions with a wet Amazon. Uplift of the Andes in the late Cenozoic (?) and consequent intensification of SASM convection (Poulsen et al. 2010; Garreaud et al. 2010) likely enhanced cooling of the EEP (Takahashi and Battisti 2007), perhaps further wetting the Amazon, but confounding attribution to any particular forcing.

H1d A steady increase of precipitation and runoff in the Amazon results from the steadily increasing width of the Atlantic throughout the Cenozoic.

Reconstructed precipitation and runoff compared to Atlantic spreading history.

Our preliminary climate modeling (Liu et al. in preparation) indicates significantly increasing TSA precipitation with Atlantic widening. This forcing has not been incorporated in previous models of TSA. Is there empirical evidence? Again, attribution to any particular cause may be difficult.

H1e On millennial and orbital timescales during the Quaternary, wetter conditions in the Amazon coincide with cold periods in the North Atlantic (Heinrich events, stadials, glacial stages), possibly associated with decreased AMOC, possibly due to a southward dislocation of the Atlantic ITCZ.

High-resolution reconstruction of runoff (especially Ti/Ca, Arz et al., 1998; Nace et al.,2014) correlated with SST (alkenone or Mg/Ca pelagic foraminifers). Analysis of pollen compositional changes at the same sampling intervals.

H1e could be called the “Shifted ITCZ hypothesis.” There are to date no climate modeling results that link an ITCZ shift to the climate dynamics of the SASM monsoon domain. We expect to recover complete Quaternary sequences deposited at rates ~0.5 mm/a. We expect to be able to observe decadal to orbital scale climate and ecosystem variability (e.g., continental precipitation, pollen composition) and climate forcing (e.g., SST) over the whole Quaternary at unprecedented resolution. We expect this record to allow a test of the refugia hypothesis. We also expect to learn about climate variation in TSA in the entirely unknown pre-Quaternary record that will comprise 95% of what we expect to recover.

Vegetation composition and biodiversity hypotheses H2a

Plant palynomorph diversity is correlated with trends in the Cenozoic deep-sea δ18O record, with highest diversity during global warm periods, such as the PETM and the middle Miocene Climatic Optimum.

Analysis of the terrestrial palynomorph record as a proxy for land plant biodiversity.

Jaramillo et al. (2006) observed a trend of palynomorph diversity (in N.TSA) that was similar to the Zachos curve with maximum diversity in the Eocene.Morley (2000, 2010), by contrast, summarized data consistent with the “museum model” indicating ever-increasing diversity through the Cenozoic. Hoorn et al. (2010) presented data consistent with the “cradle model” with many taxa apparently arising coincident with the uplift of the Andes. This all matters, because the fate of tropical forests in global warming may plausibly depend on adaptation history of modern lineages to past climate (Dick et al. 2013).

H2b Prior to onset of west to east trans-continental drainage, the marine record of palynomorph diversity shows a gradual increase in the number of species through time as species evolve to fillever-increasing ecological niches. This is a revised statement of the “museum model” that we introduced in the proposal.

Analysis of the terrestrial palynomorph record as a proxy for land plant biodiversity. Before the trans-continental Amazon was established, pollen provenance is only from the eastern Amazon. After establishment of the trans-continental Amazon, pollen provenance is basin-wide.

Similar to above. It is important to analyze pollen for each region of the Amazon, understanding that one record cannot suffice for the whole basin. For example, terSteege et al. (2011) showed nearly complete turnover of modern tree species between sites ca. 1000 km apart. The IODP sites comprise one of six localities to be drilled on the Trans-Amazon Drilling Project.

H2c Glacial-age plant communities were different in

Analysis of the terrestrial palynomorph record in the high- resolution Quaternary sections that we will recover. This will be

This will be the first complete Quaternary record, capturing many glacial and interglacial stages and Heinrich interstadials, thus affording the first

composition than interglacial forests.

tricky because of the many possible sources of the pollen, but we expect that we can successfully attribute pollen to locality taking advantage of modern techniques in organic geochemical and provenance analysis.

definitive test of the “refuge hypothesis” (Haffer, 1969), enabling an evaluation of the magnitude and causes of changes in forest composition during glacial times, which has been greatly debated (e.g. Bush et al., 2004, versus D’Apolito et al., 2013, and Wang et al., 2016).

Paleohydrology Hypothesis H3

West-to-east transcontinental Amazon drainage was initiated in the Plio-Pleistocene, far later than, and completely unrelated to, major uplift of the Andes.

Date the first terrigenous-dominated sediments overlying the carbonate platform. Date the inflection points of sediment accumulation rate. Date the shift from eastern- to Amazon basin-wide provenance. Date the onset of Andean provenance using clay mineralogy, isotope geochemistry (especially NdIR, U/Pb, SrIR), organic geochemistry, and palynology

A widespread belief is that Andean uplift and eastward transcontinental drainage were related and co-occurred around 10 Ma. However, there are many other possibilities. We believe that: (i) Andean uplift occurred asynchronously along the cordillera and, generally, far earlier than 10 Ma and (ii) eastward transcontinental drainage was far later than 10 Ma coincident with the order of magnitude increase of sedimentation offshore. Both events have major significance for biotic diversification, regional and perhaps global climate, and hydrology (e.g. Ribas et al., 2012; Baker et al., 2014)

Table 2. Drilling Outcome Scenarios

Drill site

Predicted stratigraphic sequence

Expected outcomes Best case scenario

Expected outcomes Medium case scenario

Primary Site AM-3B

From seabed to 955 mbsf, shales and sandstones. From 955 to 1631 mbsf, carbonates (calcarenites and calcilutites)

Drill the entire Quaternary-to-late Eocene section with high recovery. Recover with (over-lapping APCs) the complete Quaternary with few unconformities, at a very high mean sedimentation rate ~0.5 mm a-1. We expect to record decadal variability (5 mm); fine structure within Heinrich-type events of centennial-to-millennial duration; precessional cycles. Glacial-interglacial stages and large sea-level variations will be manifested as changes in dominant sediment type, in the Pliocene/early Pleistocene obliquity-dominated periods and in late Pleistocene/Holocene eccentricity-dominated periods. Record the timing of the changes in provenance, sedimentation rate, and paleoenvironment associated with establishment of the trans-continental Amazon. Record the sedimentary compositional and isotopic changes in the late Miocene to late Eocene during the development of the carbonate platform before the initiation of the Amazon River transcontinental drainage. Late Eocene to mid-Miocene sedimentary records are completely unknown in the Brazilian Amazon, save for scant mention in studies associated with petroleum exploration, and only very poorly known offshore (e.g., Hoorn et al., 2017). Drill core recovered from this period will permit qualitative advances in our knowledge of the provenance, paleoclimate, paleobiotic, and oceanographic history of the tropical South American continent and the adjacent Atlantic Ocean during early Cenozoic warm climates.

It seems most likely that the upper sequence (to 903 m, 1.98 Ma) can be fully recovered with over-lapping APCs. This alone would provide the longest/oldest, continuous or nearly continuous, detailed record of the Quaternary climate and biota of whole Amazon basin, post trans-continental drainage. It would also provide the similarly highest-resolution tropical Atlantic paleoceanographic record of the surface and shallow bottom water, that plays a major role in climate forcing of the adjacent continent. We expect to be able to resolve decadal to orbital scale variability during this latest and critical phase of Amazon history when ~50% of the present-day plant species of the neotropcis originated. These Quaternary records will set straight the nature of Quaternary biotic variation addressing the refuge hypothesis and the role of climate variation in diversification (and extinction). Drilling to 955 m will reach the 8 Ma horizon (Tortonian), adding information on the large sea-level variation manifested as changes in dominant sediment type, in the Pliocene/early Pleistocene obliquity-dominated periods and in late Pleistocene/Holocene eccentricity-dominated periods. Somewhere in this interval, we will recover the record of the onset of trans-Amazon drainage with Andean provenance. Drilling deeper will allow us to recover a major change in plant composition, those taxa restricted to the eastern basin. Drilling to 1252 m will reach the lower Miocene (17.7 Ma) registering the environmental changes to most of the Neogene.

Primary From seabed to 718 Drill to the late Paleocene to recover a nearly Drilling from seabed to 528 m will provide a detailed,

Site AM-7A

mbsf, shales and sandstones. From 718 to 1343 mbsf, carbonates (calcarenites and calcilutites). From 1343 to 2203 mbsf, calcarenites, calcilutites, shales and sandstones.

complete Cenozoic sequence with good stratigraphic continuity in most intervals to provide a regional record of the early development of the forest/savannah and climate of the easternmost Amazon. Reconstruct the Cenozoic continental temperature and precipitation of the easternmost tropical South America and compare with the “Zachos” deep-sea δ18O record. Record the changes in plant diversity and provenance associated with establishment of the trans-continental drainage. Collect detailed plant palynomorph data to investigate the variation of plant diversity throughout most of the Cenozoic, with focus on the completely unknown PETM record of the Amazon forest, answering critically important questions about biodiversity during former greenhouse climates. Record the surface- and shallow-bottom-water paleoceanographic record of the little-known early Cenozoic equatorial Atlantic.

high-resolution record of most of the Quaternary (to 1.98 Ma), a companion to the AM-3B. Again, we would expect to recover decadal to orbital-scale variability of paleo-environmental conditions onshore and offshore. Drilling from seabed to 718 m will reach the 8 Ma horizon (Tortonian), adding information on the large sea-level variation manifested as changes in dominant sediment type, in the Pliocene/early Pleistocene obliquity-dominated periods and in late Pleistocene/Holocene eccentricity-dominated periods. This interval would also record the sediment compositional and isotopic changes in the late Miocene, after the increased Amazon derived sedimentation. Record the changes in plant diversity after the establishment of the trans-continental drainage. Record the changes in lithology, mineralogy, geochemistry, and the presence of plant taxa restricted to the Andes. Drilling to 1093 m will reach the lower Miocene (17.7 Ma) and record the paleo-environmental history of most of the Neogene. Drilling to 1343 m will reach the 38 Ma horizon, adding information to the upper Eocene, helping to reconstruct most of the Cenozoic continental temperature and precipitation of the easternmost tropical South America during the initial stages of Antarctic ice sheet development.

Alternate Site AM-8A


Similar to AM-3B above Similar to AM-3B above

Alternate Site

From seabed to 988 mbsf, shales and


AM-13A sandstones. From 988 to 1519 mbsf, carbonates (calcarenites and calcilutites)








From seabed to 909 mbsf, shales and sandstones. From 909 to 1330 mbsf, carbonates (calcarenites and calcilutites). From 1330 to 1995 mbsf, calcarenites, calcilutites, shales and sandstones.

Similar to AM-7A above Similar to AM-7A above


From seabed to 988 mbsf, shales and sandstones. From 988 to 1468 mbsf,


carbonates (calcarenites and calcilutites). From 1468 to 2213 mbsf, calcarenites, calcilutites, shales and sandstones.




Alternate Site AM-4B



Documents

Proposal Response Letter - iodp.tamu.eduiodp.tamu.edu/scienceops/precruise/amazon/859-PRL_Baker_FOR_WEB.pdf · Proponents Response Letter: Amazon 859-Full2 Proponents: Paul A. Baker,