Brian Zimmer - Academia.edu (original) (raw)
Papers by Brian Zimmer
Nature, 2021
Bipedal trackways discovered in 1978 at Laetoli site G, Tanzania and dated to 3.66 million years ... more Bipedal trackways discovered in 1978 at Laetoli site G, Tanzania and dated to 3.66 million years ago are widely accepted as the oldest unequivocal evidence of obligate bipedalism in the human lineage1–3. Another trackway discovered two years earlier at nearby site A was partially excavated and attributed to a hominin, but curious affinities with bears (ursids) marginalized its importance to the paleoanthropological community, and the location of these footprints fell into obscurity3–5. In 2019, we located, excavated and cleaned the site A trackway, producing a digital archive using 3D photogrammetry and laser scanning. Here we compare the footprints at this site with those of American black bears, chimpanzees and humans, and we show that they resemble those of hominins more than ursids. In fact, the narrow step width corroborates the original interpretation of a small, cross-stepping bipedal hominin. However, the inferred foot proportions, gait parameters and 3D morphologies of foot...
Bulletin of Volcanology, 2010
Palaeogeography, Palaeoclimatology, Palaeoecology, 2016
Geological Society of America Abstracts with Programs, Nov 7, 2012
Our department uses its location in the Blue Ridge Mountains of northwestern North Carolina for f... more Our department uses its location in the Blue Ridge Mountains of northwestern North Carolina for field trips at all levels of our curriculum. Many of these outcrops are at road cuts open to the public and suitable for visits by large numbers of students and teachers. An outcrop of the Blowing Rock Gneiss (BRG—1.1 Ga) on US-321 south of Blowing Rock, NC includes phases of high and low grade regional metamorphism (augen gneiss and greenstone), distinct episodes of felsic and mafic intrusion, and late-forming joints similar ...
AGU Fall Meeting Abstracts, Dec 1, 2010
The Lake Natron Homo sapiens footprint site is located in northern Tanzania along the East Africa... more The Lake Natron Homo sapiens footprint site is located in northern Tanzania along the East African Rift escarpment. The site is positioned south of Lake Natron within an ephemeral channel of the Engare Sero River. The hominid footprints are preserved in a tuff, which originated from one of the volcanic centers surrounding the site. Two large volcanoes in the surrounding region, including the active carbonatite producing Oldoinyo L'engai and the now extinct Kerimasi are possible sources. This area also contains over 30 smaller tuff ...
Quaternary Science Reviews
The Science of Nature
The Placerias/Downs’ Quarry complex in eastern Arizona, USA, is the most diverse Upper Triassic v... more The Placerias/Downs’ Quarry complex in eastern Arizona, USA, is the most diverse Upper Triassic vertebrate locality known. We report a new short-faced archosauriform, Syntomiprosopus sucherorum gen. et sp. nov., represented by four incomplete mandibles, that expands that diversity with a morphology unique among Late Triassic archosauriforms. The most distinctive feature of Syntomiprosopus gen. nov. is its anteroposteriorly short, robust mandible with 3–4 anterior, a larger caniniform, and 1–3 “postcanine” alveoli. The size and shape of the alveoli and the preserved tips of replacement teeth preclude assignment to any taxon known only from teeth. Additional autapomorphies of S. sucherorum gen. et sp. nov. include a large fossa associated with the mandibular fenestra, an interdigitating suture of the surangular with the dentary, fine texture ornamenting the medial surface of the splenial, and a surangular ridge that completes a 90° arc. The external surfaces of the mandibles bear shal...
Soil Science Society of America Journal, 2007
The Southern Cordillera and Beyond, 2012
Geological Society of America Abstracts with Programs, Nov 7, 2012
Our department uses its location in the Blue Ridge Mountains of northwestern North Carolina for f... more Our department uses its location in the Blue Ridge Mountains of northwestern North Carolina for field trips at all levels of our curriculum. Many of these outcrops are at road cuts open to the public and suitable for visits by large numbers of students and teachers. An outcrop of the Blowing Rock Gneiss (BRG—1.1 Ga) on US-321 south of Blowing Rock, NC includes phases of high and low grade regional metamorphism (augen gneiss and greenstone), distinct episodes of felsic and mafic intrusion, and late-forming joints similar ...
We report on the radioisotopic age, formation, and preservation of a late Pleistocene human footp... more We report on the radioisotopic age, formation, and preservation of a late Pleistocene human footprint site in northern Tanzania on the southern shore of Lake Natron near the village of Engare Sero. Over 400 human footprints , as well as tracks of zebra and bovid, are preserved in a series of volcaniclastic deposits. Based on field mapping along with geochemical and grain-size analyses, we propose that these deposits originated as proximal volcanic material from the nearby active volcano, Oldoinyo L'engai, and were then fluvially transported to the footprint site. Stable isotope results (δ 18 O and δ 13 C) suggest that the footprints were originally emplaced on a mudflat saturated by a freshwater spring and were later inundated by the rising alkaline waters of Lake Natron. We employed the 40 Ar/ 39 Ar and 14 C dating methods to investigate the age of the site and determined that the footprint level is older than 5760 ± 30 yrs. BP and younger than 19.1 ± 3.1 ka. These radioisotopic ages are supported by stratigraphic correlations with previously documented debris avalanche deposits and the stable isotope signatures associated with the most recent highstand of Lake Natron, further constraining the age to latest Pleistocene. Since modern humans (Homo sapiens) were present in Africa ca. 200 ka, Engare Sero represents the most abundant and best-preserved footprint site of anatomically modern Homo sapiens currently known in Africa. Fossil footprints are a snapshot in time, recording behavior at a specific moment in history; but the actual duration of time captured by the snapshot is often not well defined. Through analog experiments, we constrain the depositional window in which the prints were made, buried, and ultimately preserved to within a few hours to days or months.
ABSTRACT Cerro Pinto is a rhyolite dome complex located in the eastern Trans-Mexican Volcanic Bel... more ABSTRACT Cerro Pinto is a rhyolite dome complex located in the eastern Trans-Mexican Volcanic Belt. The complex is composed of four tuff rings and four domes that were emplaced in three distinct eruptive stages marked by changes in vent location and eruptive character. Each of these stages contained eruptive sequences that follow simple rhyolite-dome models, in which a pyroclastic phase is followed immediately by effusive dome emplacement. However, some aspects of the eruptive history, such as the occurrence of explosive reactivation and dome destruction through a lateral blast are uncommon in small rhyolitic structures and are more commonly associated with polygenetic structures, such as stratovolcanoes or calderas. In these larger structures, new pulses of magma often initiate reactivation, but at Cerro Pinto the story is different. Major and trace element geochemistry suggest that Cerro Pinto was sourced by a small, isolated magma chamber, unassociated with any surrounding silicic centers and did not experience any change in chemical composition over the course of the eruption. Based on these data and field observations, it is inferred that Cerro Pinto's eruptive variations were not the result of the influx of a new magma batch, but were the result of both phreatomagmatic interactions and the presence of a small magma chamber that was zoned with respect to volatiles. Both of these factors are commonly encountered in volcanologic studies, but documentation of their influence on smaller structures is under represented. Rhyolite domes have long been considered relatively simple volcanic structures with only localized hazard implications. However, the eruptive variations displayed by Cerro Pinto suggest that isolated rhyolite dome evolutions can be much more complex with the potential for explosive reactivation and dome collapse; events that must be taken into consideration when making hazard assessments.
The Southern Cordillera and Beyond, 2012
Bulletin of Volcanology, 2010
Geological Society of America Abstracts with Programs, Nov 7, 2012
Our department uses its location in the Blue Ridge Mountains of northwestern North Carolina for f... more Our department uses its location in the Blue Ridge Mountains of northwestern North Carolina for field trips at all levels of our curriculum. Many of these outcrops are at road cuts open to the public and suitable for visits by large numbers of students and teachers. An outcrop of the Blowing Rock Gneiss (BRG—1.1 Ga) on US-321 south of Blowing Rock, NC includes phases of high and low grade regional metamorphism (augen gneiss and greenstone), distinct episodes of felsic and mafic intrusion, and late-forming joints similar ...
AGU Fall Meeting Abstracts, Dec 1, 2010
The Lake Natron Homo sapiens footprint site is located in northern Tanzania along the East Africa... more The Lake Natron Homo sapiens footprint site is located in northern Tanzania along the East African Rift escarpment. The site is positioned south of Lake Natron within an ephemeral channel of the Engare Sero River. The hominid footprints are preserved in a tuff, which originated from one of the volcanic centers surrounding the site. Two large volcanoes in the surrounding region, including the active carbonatite producing Oldoinyo L'engai and the now extinct Kerimasi are possible sources. This area also contains over 30 smaller tuff ...
Nature, 2021
Bipedal trackways discovered in 1978 at Laetoli site G, Tanzania and dated to 3.66 million years ... more Bipedal trackways discovered in 1978 at Laetoli site G, Tanzania and dated to 3.66 million years ago are widely accepted as the oldest unequivocal evidence of obligate bipedalism in the human lineage1–3. Another trackway discovered two years earlier at nearby site A was partially excavated and attributed to a hominin, but curious affinities with bears (ursids) marginalized its importance to the paleoanthropological community, and the location of these footprints fell into obscurity3–5. In 2019, we located, excavated and cleaned the site A trackway, producing a digital archive using 3D photogrammetry and laser scanning. Here we compare the footprints at this site with those of American black bears, chimpanzees and humans, and we show that they resemble those of hominins more than ursids. In fact, the narrow step width corroborates the original interpretation of a small, cross-stepping bipedal hominin. However, the inferred foot proportions, gait parameters and 3D morphologies of foot...
Bulletin of Volcanology, 2010
Palaeogeography, Palaeoclimatology, Palaeoecology, 2016
Geological Society of America Abstracts with Programs, Nov 7, 2012
Our department uses its location in the Blue Ridge Mountains of northwestern North Carolina for f... more Our department uses its location in the Blue Ridge Mountains of northwestern North Carolina for field trips at all levels of our curriculum. Many of these outcrops are at road cuts open to the public and suitable for visits by large numbers of students and teachers. An outcrop of the Blowing Rock Gneiss (BRG—1.1 Ga) on US-321 south of Blowing Rock, NC includes phases of high and low grade regional metamorphism (augen gneiss and greenstone), distinct episodes of felsic and mafic intrusion, and late-forming joints similar ...
AGU Fall Meeting Abstracts, Dec 1, 2010
The Lake Natron Homo sapiens footprint site is located in northern Tanzania along the East Africa... more The Lake Natron Homo sapiens footprint site is located in northern Tanzania along the East African Rift escarpment. The site is positioned south of Lake Natron within an ephemeral channel of the Engare Sero River. The hominid footprints are preserved in a tuff, which originated from one of the volcanic centers surrounding the site. Two large volcanoes in the surrounding region, including the active carbonatite producing Oldoinyo L'engai and the now extinct Kerimasi are possible sources. This area also contains over 30 smaller tuff ...
Quaternary Science Reviews
The Science of Nature
The Placerias/Downs’ Quarry complex in eastern Arizona, USA, is the most diverse Upper Triassic v... more The Placerias/Downs’ Quarry complex in eastern Arizona, USA, is the most diverse Upper Triassic vertebrate locality known. We report a new short-faced archosauriform, Syntomiprosopus sucherorum gen. et sp. nov., represented by four incomplete mandibles, that expands that diversity with a morphology unique among Late Triassic archosauriforms. The most distinctive feature of Syntomiprosopus gen. nov. is its anteroposteriorly short, robust mandible with 3–4 anterior, a larger caniniform, and 1–3 “postcanine” alveoli. The size and shape of the alveoli and the preserved tips of replacement teeth preclude assignment to any taxon known only from teeth. Additional autapomorphies of S. sucherorum gen. et sp. nov. include a large fossa associated with the mandibular fenestra, an interdigitating suture of the surangular with the dentary, fine texture ornamenting the medial surface of the splenial, and a surangular ridge that completes a 90° arc. The external surfaces of the mandibles bear shal...
Soil Science Society of America Journal, 2007
The Southern Cordillera and Beyond, 2012
Geological Society of America Abstracts with Programs, Nov 7, 2012
Our department uses its location in the Blue Ridge Mountains of northwestern North Carolina for f... more Our department uses its location in the Blue Ridge Mountains of northwestern North Carolina for field trips at all levels of our curriculum. Many of these outcrops are at road cuts open to the public and suitable for visits by large numbers of students and teachers. An outcrop of the Blowing Rock Gneiss (BRG—1.1 Ga) on US-321 south of Blowing Rock, NC includes phases of high and low grade regional metamorphism (augen gneiss and greenstone), distinct episodes of felsic and mafic intrusion, and late-forming joints similar ...
We report on the radioisotopic age, formation, and preservation of a late Pleistocene human footp... more We report on the radioisotopic age, formation, and preservation of a late Pleistocene human footprint site in northern Tanzania on the southern shore of Lake Natron near the village of Engare Sero. Over 400 human footprints , as well as tracks of zebra and bovid, are preserved in a series of volcaniclastic deposits. Based on field mapping along with geochemical and grain-size analyses, we propose that these deposits originated as proximal volcanic material from the nearby active volcano, Oldoinyo L'engai, and were then fluvially transported to the footprint site. Stable isotope results (δ 18 O and δ 13 C) suggest that the footprints were originally emplaced on a mudflat saturated by a freshwater spring and were later inundated by the rising alkaline waters of Lake Natron. We employed the 40 Ar/ 39 Ar and 14 C dating methods to investigate the age of the site and determined that the footprint level is older than 5760 ± 30 yrs. BP and younger than 19.1 ± 3.1 ka. These radioisotopic ages are supported by stratigraphic correlations with previously documented debris avalanche deposits and the stable isotope signatures associated with the most recent highstand of Lake Natron, further constraining the age to latest Pleistocene. Since modern humans (Homo sapiens) were present in Africa ca. 200 ka, Engare Sero represents the most abundant and best-preserved footprint site of anatomically modern Homo sapiens currently known in Africa. Fossil footprints are a snapshot in time, recording behavior at a specific moment in history; but the actual duration of time captured by the snapshot is often not well defined. Through analog experiments, we constrain the depositional window in which the prints were made, buried, and ultimately preserved to within a few hours to days or months.
ABSTRACT Cerro Pinto is a rhyolite dome complex located in the eastern Trans-Mexican Volcanic Bel... more ABSTRACT Cerro Pinto is a rhyolite dome complex located in the eastern Trans-Mexican Volcanic Belt. The complex is composed of four tuff rings and four domes that were emplaced in three distinct eruptive stages marked by changes in vent location and eruptive character. Each of these stages contained eruptive sequences that follow simple rhyolite-dome models, in which a pyroclastic phase is followed immediately by effusive dome emplacement. However, some aspects of the eruptive history, such as the occurrence of explosive reactivation and dome destruction through a lateral blast are uncommon in small rhyolitic structures and are more commonly associated with polygenetic structures, such as stratovolcanoes or calderas. In these larger structures, new pulses of magma often initiate reactivation, but at Cerro Pinto the story is different. Major and trace element geochemistry suggest that Cerro Pinto was sourced by a small, isolated magma chamber, unassociated with any surrounding silicic centers and did not experience any change in chemical composition over the course of the eruption. Based on these data and field observations, it is inferred that Cerro Pinto's eruptive variations were not the result of the influx of a new magma batch, but were the result of both phreatomagmatic interactions and the presence of a small magma chamber that was zoned with respect to volatiles. Both of these factors are commonly encountered in volcanologic studies, but documentation of their influence on smaller structures is under represented. Rhyolite domes have long been considered relatively simple volcanic structures with only localized hazard implications. However, the eruptive variations displayed by Cerro Pinto suggest that isolated rhyolite dome evolutions can be much more complex with the potential for explosive reactivation and dome collapse; events that must be taken into consideration when making hazard assessments.
The Southern Cordillera and Beyond, 2012
Bulletin of Volcanology, 2010
Geological Society of America Abstracts with Programs, Nov 7, 2012
Our department uses its location in the Blue Ridge Mountains of northwestern North Carolina for f... more Our department uses its location in the Blue Ridge Mountains of northwestern North Carolina for field trips at all levels of our curriculum. Many of these outcrops are at road cuts open to the public and suitable for visits by large numbers of students and teachers. An outcrop of the Blowing Rock Gneiss (BRG—1.1 Ga) on US-321 south of Blowing Rock, NC includes phases of high and low grade regional metamorphism (augen gneiss and greenstone), distinct episodes of felsic and mafic intrusion, and late-forming joints similar ...
AGU Fall Meeting Abstracts, Dec 1, 2010
The Lake Natron Homo sapiens footprint site is located in northern Tanzania along the East Africa... more The Lake Natron Homo sapiens footprint site is located in northern Tanzania along the East African Rift escarpment. The site is positioned south of Lake Natron within an ephemeral channel of the Engare Sero River. The hominid footprints are preserved in a tuff, which originated from one of the volcanic centers surrounding the site. Two large volcanoes in the surrounding region, including the active carbonatite producing Oldoinyo L'engai and the now extinct Kerimasi are possible sources. This area also contains over 30 smaller tuff ...