Synchrony between the Central Atlantic magmatic province and the Triassic-Jurassic mass-extinction event?

We present new data and a synthesis of cyclostratigraphic, lithostratigraphic, biostratigraphic, and published magnetostratigraphic and basalt geochemical data from eastern North America and Morocco in an attempt to clarify the temporal relationship between the Triassic–Jurassic mass extinction (∼ 202 Ma) and Earth's largest sequence of continental flood basalts, the Central Atlantic magmatic province (CAMP). Newly discovered zones of reverse polarity within CAMP flow sequences of Morocco have been hypothesized by Marzoli et al. [Marzoli, A., Bertrand, H., Knight, K.B., Cirilli, S., Buratti, N., Vérati, C., Nomade, S., Renne, P.R., Youbi, N., Martini, R., Allenbach, K., Neuwerth, R., Rapaille, C., Zaninetti, L., Bellieni, G., 2004. Synchrony of the Central Atlantic magmatic province and the Triassic–Jurassic boundary climatic and biotic crisis. Geology 32, 973–976.] and Knight et al. [Knight, K.B., Nomade, S., Renne, P.R., Marzoli, A., Betrand, H., Youbi, N., 2004. The Central Atlantic Magmatic Province at the Triassic–Jurassic boundary: paleomagnetic and 40Ar/30Ar evidence from Morocco for brief, episodic volcanism. Earth and Planetary Science Letters 228, 143–160.] as correlates of a very short, uppermost Triassic age reverse chron in the Newark basin, thus suggesting that much of the Moroccan CAMP was synchronous with or predates the Triassic–Jurassic boundary. Here, however, we explain these apparent reverse polarity zones as possible correlatives of poorly sampled lower Jurassic basalt flow sequences and overlying strata in eastern North America and lower Jurassic reverse polarity sequences recognized by others in the Paris basin. A revised Milankovitch cyclostratigraphy based on new core and field data constrains the duration of eastern North America basaltic flows to ∼ 610 ky after the Triassic–Jurassic palynological turnover event. Palynological data indicates correlation of the initial carbon isotopic excursion of Hesselbo et al. [Hesselbo, S.P., Robinson, S.A., Surlyk, F., Piasecki, S., 2002. Terrestrial and marine extinction at the Triassic–Jurassic boundary synchronized with major carbon-cycle perturbation: a link to initiation of massive volcanism. Geology 30, 251–254.] at St. Audrie's Bay to the palynological turnover event and vertebrate extinction level in eastern North America, suggesting a revised magnetostratigraphic correlation and robust carbon isotopic tests of the Marzoli–Knight hypothesis. We conclude that as yet there are no compelling data showing that any of the CAMP predated or was synchronous with the Triassic–Jurassic extinction event

Synchrony between the Central Atlantic magmatic province and the Triassic-Jurassic mass-extinction event? Reply to Marzoli et al.

We are very pleased with the attention, long overdue, that the Triassic–Jurassic boundary and associated events, such as the CAMP, are receiving. This can only lead to greater specificity of hypotheses and greater understanding in the long run, and it is worth emphasizing some broad areas of agreement. Marzoli et al. (2008-this volume) points out the closeness in time of CAMP and Tr–J extinctions, and on this we all agree. We also agree that the systematic differences among different isotopic systems used for dating is a challenge to determining the relative timing of events dated with different techniques. This problem, however, seem to be fading as high-precision single-crystal U–Pb dates (206Pb/238U) are available from a variety of tuffs interbedded with marine strata as well as the North Mountain Basalt of Nova Scotia, which lies above the palynological Triassic–Jurassic extinction event in Nova Scotia. Schoene et al. (2006) obtained an age of 201.27 ± 0.03 Ma from this basalt, which is very close to an age of 201.5 Ma for a tuff 1 m above the last local occurrence of the topmost Triassic guide-fossil, the ammonite Choristoceras in a marine section in Peru (Schaltegger et al., 2007), presumably very close to the Triassic–Jurassic extinction event. Schaltegger et al. (2007) also obtained an age of 199.5 Ma for the Hettangian–Sinemurian boundary from the latter section. Consistent with these ages, Pálfy and Mundil (2006) obtained ages of 200.6 ± 0.3 Ma for an ash layer in ammonite-bearing Middle Hettangian marine sediments in, Alaska, and 198.0 ± 0.6 Ma for a tuff layer in Early Sinemurian sediments in Hungary. These dates are not compatible with the multi-crystal age for the Triassic–Jurassic boundary of 199.6 ± 0.3 Ma of Pálfy and Mundil (2006), a fact recognized by Pálfy and Mundil (2006). Thus, we are in complete agreement that the Triassic–Jurassic extinction event is extremely close in time to the onset of the CAMP. The question is, "are any of the known flows of the CAMP actually at or before this extinction event?". That is the key issue dealt with by Whiteside et al. (2007), and it is a possibility that we recognize as completely plausible, but not yet demonstrated. It is in that spirit of general agreement that we reply to Marzoli et al.'s, comment. We note, however, that their comment touches on far too many points to adequately address in this reply, and we chose to focus our response on their most substantive issues, recalling that our paper was focusing on the testable aspects of their overall hypothesis. We deal with their criticisms in the order they present them

Implications of a comparison of the stratigraphy and depositional environments of the Argana (Morocco) and Fundy (Nova Scotia, Canada) Permian-Jurassic basins

The Argana rift basin of Morocco and the Fundy rift basin of the Maritime Provinces of Eastern Canada are on the conjugate margins of the central Atlantic Ocean. In the Late Triassic and Early Jurassic these basins lie at similar paleolatitudes within the same great rift system. A comparison of the depositional- and tectono-stratigraphy reveal strong similarities, much greater that those shared between the Fundy basin and other rifts in eastern North America. Both the Argana and Fundy basins are comprised of four, mostly unconformity-bound, tectonostratigraphic sequences (TS I-IV) probably controlled by pulses of extension: TS I, is Permian in age and the depositional facies of the Argana basin looks more humid than the age equivalent in the Fundy basin and the latter may not be a rift sequence; TS II, is early Late Triassic (Carnian) in age and is the most humid looking facies in both basins; TS III, is late Late Triassic (Norian and Rhaetian) in age and is much more arid in both basins with abundant aeolianites and evaporites; TS IV, is latest Triassic and earliest Jurassic (late Rhaetian - early Hettangian) and shows an increase in the range of variability in climate-sensitive facies - its basal part contains the Triassic-Jurassic boundary an overlying basalt flow sequence and additional fluvial and lacustrine strata on top. The dramatic similarity in both facies and sequence stratigraphy between the Argana and Fundy basins, at least during the Triassic, argues for similar tectonic control, restricted to that latitudinal swath of Pangea, as well as similar paleoclimate

Response to Comment on "Ascent of Dinosaurs Linked to an Iridium Anomaly at the Triassic-Jurassic Boundary"

Our recent study on the nature of the ascent of the dinosaurs (1) argued three main points: (i) that a major terrestrial tetrapod mass extinction is concentrated at the palynologically identified Triassic-Jurassic boundary in eastern North America (based on footprints and bones); (ii) that truly large predatory dinosaurs appear immediately after the boundary (based on footprints); and (iii) that both the boundary and the mass extinction level are associated with a modest Ir anomaly and fern spike, plausibly of asteroid or comet impact origin. Although the comment of Thulborn (2) addresses a number of paleontological issues in (1), his only point salient to the conclusions of our paper is his extraordinary claim that very large theropod dinosaurs were already present in the Carnian, some 20 million years or so before the Triassic-Jurassic boundary [in contrast to our assertion in point (ii), above]

Continental Triassic-Jurassic Boundary in Central Pangea: Recent Progress and Discussion of an Ir Anomaly

The Triassic-Jurassic (Tr-J) boundary marks one of the five largest mass extinctions in the past 0.5 b.y. In many of the exposed rift basins of the Atlantic passive margin of eastern North America and Morocco, the boundary is identified as an interval of stratigraphically abrupt floral and faunal change within cyclical lacustrine sequences. A comparatively thin interval of Jurassic strata separates the boundary from extensive overlying basalt flows, the best dates of which (ca. 202 Ma) are practically indistinguishable from recent dates on tuffs from marine Tr-J boundary sequences. The pattern and magnitude of the Tr-J boundary at many sections spanning more than 10° of paleolatitude in eastern North America and Morocco are remarkably similar to those at the Cretaceous-Tertiary boundary, sparking much debate on the cause of the end-Triassic extinctions, hypotheses focusing on bolide impacts and climatic changes associated with flood basalt volcanism. Four prior attempts at finding evidence of impacts at the Tr-J boundary in these rift basin localities were unsuccessful. However, after more detailed sampling, a modest Ir anomaly has been reported (up to 285 ppt, 0.29 ng/g) in the Newark rift basin (New York, New Jersey, Pennsylvania, United States), and this anomaly is directly associated with a fern spike. A search for shocked quartz in these rift basins has thus far been fruitless. Although both the microstratigraphy and the biotic pattern of the boundary are very similar to continental Cretaceous-Tertiary boundary sections in the western United States, we cannot completely rule out a volcanic, or other nonimpact, hypothesis using data currently available

Ascent of Dinosaurs Linked to an Iridium Anomaly at the Triassic-Jurassic Boundary

Analysis of tetrapod footprints and skeletal material from more than 70 localities in eastern North America shows that large theropod dinosaurs appeared less than 10,000 years after the Triassic-Jurassic boundary and less than 30,000 years after the last Triassic taxa, synchronous with a terrestrial mass extinction. This extraordinary turnover is associated with an iridium anomaly (up to 285 parts per trillion, with an average maximum of 141 parts per trillion) and a fern spore spike, suggesting that a bolide impact was the cause. Eastern North American dinosaurian diversity reached a stable maximum less than 100,000 years after the boundary, marking the establishment of dinosaur-dominated communities that prevailed for the next 135 million years

Synchrony between the Central Atlantic magmatic province and the Triassic–Jurassic mass-extinction event?

We present new data and a synthesis of cyclostratigraphic, lithostratigraphic, biostratigraphic, and published magnetostratigraphic and basalt geochemical data from eastern North America and Morocco in an attempt to clarify the temporal relationship between the Triassic–Jurassic mass extinction (? 202 Ma) and Earth's largest sequence of continental flood basalts, the Central Atlantic magmatic province (CAMP). Newly discovered zones of reverse polarity within CAMP flow sequences of Morocco have been hypothesized by Marzoli et al. [Marzoli, A., Bertrand, H., Knight, K.B., Cirilli, S., Buratti, N., Vérati, C., Nomade, S., Renne, P.R., Youbi, N., Martini, R., Allenbach, K., Neuwerth, R., Rapaille, C., Zaninetti, L., Bellieni, G., 2004. Synchrony of the Central Atlantic magmatic province and the Triassic–Jurassic boundary climatic and biotic crisis. Geology 32, 973–976.] and Knight et al. [Knight, K.B., Nomade, S., Renne, P.R., Marzoli, A., Betrand, H., Youbi, N., 2004. The Central Atlantic Magmatic Province at the Triassic–Jurassic boundary: paleomagnetic and 40Ar/30Ar evidence from Morocco for brief, episodic volcanism. Earth and Planetary Science Letters 228, 143–160.] as correlates of a very short, uppermost Triassic age reverse chron in the Newark basin, thus suggesting that much of the Moroccan CAMP was synchronous with or predates the Triassic–Jurassic boundary. Here, however, we explain these apparent reverse polarity zones as possible correlatives of poorly sampled lower Jurassic basalt flow sequences and overlying strata in eastern North America and lower Jurassic reverse polarity sequences recognized by others in the Paris basin. A revised Milankovitch cyclostratigraphy based on new core and field data constrains the duration of eastern North America basaltic flows to ? 610 ky after the Triassic–Jurassic palynological turnover event. Palynological data indicates correlation of the initial carbon isotopic excursion of Hesselbo et al. [Hesselbo, S.P., Robinson, S.A., Surlyk, F., Piasecki, S., 2002. Terrestrial and marine extinction at the Triassic–Jurassic boundary synchronized with major carbon-cycle perturbation: a link to initiation of massive volcanism. Geology 30, 251–254.] at St. Audrie's Bay to the palynological turnover event and vertebrate extinction level in eastern North America, suggesting a revised magnetostratigraphic correlation and robust carbon isotopic tests of the Marzoli–Knight hypothesis. We conclude that as yet there are no compelling data showing that any of the CAMP predated or was synchronous with the Triassic–Jurassic extinction event

Pollen and spores from the perennial sea-ice covered environment of the central Arctic Ocean, summer 2004 (IODP ACEX 302)

We obtained three different types of samples from the central Arctic Ocean during the IODP Arctic Coring Expedition (ACEX) 302, which took place during summer 2004: they are (1) sea water, (2) sea-ice, and (3) diatom mat samples. A total of 227 specimens of pollen and spores as well as 52 pollen fragments were found in the samples. Dominant pollen taxa are vesiculate: Pinus (pines, “Matsu” in Japanese), Picea (spruce, “Touhi” in Japanese) and Abies (fir, “Momi” in Japanese). Porate pollen and monolete spores were also found, but their populations were very small. Most of the pollen grains encountered were from the sea water sample type, whereas in sea-ice or diatom mat samples pollen grains were very rare. It is most likely that these pollen grains were transported via the Arctic Current rather than via atmospheric pathways, such as the geostrophic wind

Synchrony between the Central Atlantic

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