Paleontological Investigations at the Eocene Locality of Mahenge in North-Central Tanzania, East Africa

Harrison, Terry; Msuya, Charles P.; Jacobs, Bonnie F.; Báez, Ana María; Mundil, Roland; Ludwig, K. R.

doi:10.1007/978-1-4615-1271-4_2

Cited by 40 publications

(54 citation statements)

References 78 publications

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“…3). During this same period, kimberlites were emplaced in Archean lithosphere between the Western and Eastern rift (Harrison et al, 2001), and fl anking the Southwestern rift (Batumike et al, 2007). Their widespread distribution suggests that heating and local metasomatism preceded any surface expression of rifting across the broad, uplifted plateaus.…”

Section: East African Rift Zonementioning

confidence: 94%

The time scales of continental rifting: Implications for global processes

Ebinger

Wijk

Keir

2013

The Web of Geological Sciences: Advances, Impacts, and Interactions

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The rifting cycle initiates with stress buildup, release as earthquakes and/or magma intrusions/eruptions, and visco-elastic rebound, multiple episodes of which combine to produce the observed, time-averaged rift zone architecture. The aim of our synthesis of current research initiatives into continental rifting-to-rupture processes is to quantify the time and length scales of faulting and magmatism that produce the time-averaged rift structures imaged in failed rifts and passive margins worldwide. We compare and contrast seismic and geodetic strain patterns during discrete, intense rifting episodes in magmatic and amagmatic sectors of the East African rift zone that span early-to late-stage rifting. We also examine the longer term rifting cycle and its relation to changing far-fi eld extension directions with examples from the Rio Grande rift zone and other cratonic rifts. Over time periods of millions of years, periods of rotating regional stress fi elds are marked by a lull in magmatic activity and a temporary halt to tectonic rift opening. Admittedly, rifting cycle comparisons are biased by the short time scale of global seismic and geodetic measurements, which span a small fraction of the 10 2 -10 5 year rifting cycle. Within rift sectors with upper crustal magma chambers beneath the central rift valley (e.g., Main Ethiopian, Afar, and Eastern or Gregory rifts) seismic energy release accounts for a small fraction of the deformation; most of the strain is accommodated by magma intrusion and slowslip. Magma intrusion processes appear to decrease the time period between rifting episodes, effectively accelerating the rift to rupture process. Thus, the inter-seismic period in rift zones with crustal magma reservoirs is strongly dependent upon the

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Section: East African Rift Zonementioning

confidence: 94%

The time scales of continental rifting: Implications for global processes

Ebinger

Wijk

Keir

2013

The Web of Geological Sciences: Advances, Impacts, and Interactions

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“…the tropics is included in the absence of any tropical data from the Early Eocene [100,101]. There is no data coverage at latitudes greater than 65 • S and coverage is highest in the NH particularly over North America.…”

Section: (F) Model-data Comparisonmentioning

confidence: 99%

The Early Eocene equable climate problem: can perturbations of climate model parameters identify possible solutions?

Sagoo

Valdes

Flecker

et al. 2013

Phil. Trans. R. Soc. A.

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Geological data for the Early Eocene (56–47.8 Ma) indicate extensive global warming, with very warm temperatures at both poles. However, despite numerous attempts to simulate this warmth, there are remarkable data–model differences in the prediction of these polar surface temperatures, resulting in the so-called ‘equable climate problem’. In this paper, for the first time an ensemble with a perturbed climate-sensitive model parameters approach has been applied to modelling the Early Eocene climate. We performed more than 100 simulations with perturbed physics parameters, and identified two simulations that have an optimal fit with the proxy data. We have simulated the warmth of the Early Eocene at 560 ppmv CO 2 , which is a much lower CO 2 level than many other models. We investigate the changes in atmospheric circulation, cloud properties and ocean circulation that are common to these simulations and how they differ from the remaining simulations in order to understand what mechanisms contribute to the polar warming. The parameter set from one of the optimal Early Eocene simulations also produces a favourable fit for the last glacial maximum boundary climate and outperforms the control parameter set for the present day. Although this does not ‘prove’ that this model is correct, it is very encouraging that there is a parameter set that creates a climate model able to simulate well very different palaeoclimates and the present-day climate. Interestingly, to achieve the great warmth of the Early Eocene this version of the model does not have a strong future climate change Charney climate sensitivity. It produces a Charney climate sensitivity of 2.7 ° C, whereas the mean value of the 18 models in the IPCC Fourth Assessment Report (AR4) is 3.26 ° C±0.69 ° C. Thus, this value is within the range and below the mean of the models included in the AR4.

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“…Tanzanycteris mannardi was recovered from the lacustrine Mahenge locality in north-central Tanzania. Zircon at the base of the Mahenge sequence (~1.2 m below the fossil) was 206 Pb/ 238 U dated by Harrison et al (2001) to 45.83 ± 0.17 Ma. The authors also considered sedimentation rates, for which minimum estimates and error on the 206 Pb/ 238 U dates allow a minimum bound of 45.0 Ma for T. mannardi and the crown chiropteran divergence.…”

Section: Crown Chiropteramentioning

confidence: 99%

Four mammal fossil calibrations: balancing competing palaeontological and molecular considerations

Phillips

2015

Palaeontologia Electronica

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Paleontological Investigations at the Eocene Locality of Mahenge in North-Central Tanzania, East Africa

Cited by 40 publications

References 78 publications

The time scales of continental rifting: Implications for global processes

The time scales of continental rifting: Implications for global processes

The Early Eocene equable climate problem: can perturbations of climate model parameters identify possible solutions?

Four mammal fossil calibrations: balancing competing palaeontological and molecular considerations

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