Earth History Research and News

In the latest issue of Palaeogeography, Palaeoclimatology, Palaeoecology a new explanation is offered for an extraordinarily widespread horizon of soft-sediment deformation in the lower part of the Cotham Member of the Penarth Group (latest Triassic, Rhaetian). The most parsimonious interpretation is for a major seismic event triggering in situ foundering of poorly consolidated sediments, but its exact cause remains enigmatic. The consistent position of the ‘seismite’ horizon in the lower part of the Cotham Member, the lack of any evidence for more than one deformational event, and the absence of similarly widespread phenomena in contiguous parts of the geological column, favour a single-event scenario. The authors argue that volcanism is unlikely to have been responsible and that the impact of a 2-3 km diameter asteroid offers a more attractive explanation for such a powerful seismic shock. However, no impact crater of the right age has yet been located so the bolide impact interpretation remains speculative.

Simms, M. J., ‘Uniquely extensive soft-sediment deformation in the Rhaetian of the UK: evidence for earthquake or impact?’, Palaeogeography, Palaeoclimatology, Palaeoecology 2007;244(1-4):407-423.

Abstract. The lower part of the Cotham Member in the Penarth Group (latest Triassic, Rhaetian) of the UK incorporates a uniquely extensive metre-scale horizon of soft-sediment deformation. Interpreted as a seismite, it shows evidence for only a single seismic event even at its thickest development. It is recorded from more than forty sites across at least eight discrete sedimentary basins covering > 250,000 km2, and originally must have covered a still larger area. Such a widespread horizon of soft-sediment deformation, unique for the UK Phanerozoic and implying a seismic event of exceptional magnitude, is difficult to account for by conventional terrestrial mechanisms. Contemporaneous volcanism in the Central Atlantic Magmatic Province (CAMP) was too far distant to cause the deformation, and the tectonic setting of the region was not conducive to earthquakes on this scale. Slump fold long axes suggest an epicentre broadly in the southern Irish Sea or St. George's Channel. Impact of a km-scale asteroid here potentially could produce the observed sedimentological effects across the UK, but any late Triassic impact structure would now be concealed by a km or more of younger strata. At its thickest development, in Northern Ireland, the seismite is succeeded by a rip-up breccia and hummocky- and wave-rippled cross stratification. These facies, and their position immediately above the seismite, are consistent with the effects of a tsunami arising directly from the seismic event. Tentative evidence for a tsunamite of this age has also been reported from southern France. The putative tsunamite in Northern Ireland is succeeded by a desiccation-cracked hiatus which may correlate with a similar hiatus truncating the seismite at sites in southern England. The hiatus in southern England correlates closely with a δ13C isotope excursion that has been traced from eastern Europe across to western North America and is associated with significant biotic changes. The ultimate cause of the seismite and associated tsunamite remains unclear. No impact crater of appropriate age or location is currently known and other evidence for impact at this time is at best equivocal. It is considered here that impact of a km-scale asteroid may have caused the observed sedimentological effects in the Lilstock Formation across the UK area, but was not necessarily a significant contributory factor in the generation of either the isotope excursion or of the biotic changes through the Triassic-Jurassic boundary interval.

My blog post for April 19 2006 concerned a debate in the Journal of Creation about whether the Green River Formation (Eocene of Wyoming) was deposited during or after the Flood. Michael Oard argued the case for Flood deposition and John Whitmore argued for a post-Flood lacustrine model. The papers in the debate forum have now been made available on-line. Just follow the link. Each paper can be downloaded as a pdf file.

http://www.creationontheweb.com/content/view/4509/#Forumcontents

Catastrophism is alive and well in the Middle Jurassic of Oman. This paper describes coarse debris flow deposits, incorporating very large floating clasts up to 100 m long. The sediments are interpreted as having been deposited by massive submarine slides, which were then reworked by the resulting tsunami.

Brookfield M. E., Blechschmidt I., Hannigan R., Coniglio M., Simonson B., Wilson G., ‘Sedimentology and geochemistry of extensive very coarse deepwater submarine fan sediments in the Middle Jurassic of Oman, emplaced by giant tsunami triggered by submarine mass flows’, Sedimentary Geology 2006;192(1-2):75-98.

Abstract. Unusual fining upwards coarse conglomerates overlain by sandstones, thin cherts and green shales occur at the top of the deep-water submarine fan deposits of the Oolitic Limestone Member of the Jurassic Guwayza Formation of Oman. They separate the dominantly submarine fan deposits of the Guwayza Formation from the pelagic shales, fine-grained limestones and cherts of the overlying Sidr Formation. The cross-bedded and graded framework conglomerates occur in extensive, tabular units and are dominated by earlier Mesozoic carbonate clasts with sandy oolitic and peloidal grains derived from fault escarpments and shelf sediments far to the southwest. Subordinate inverse grading, very thick beds, very large floating clasts (up to 100 m long in places) indicate deposition from catastrophic debris flows. Though most palaeocurrents indicate flow from off the platform to the southwest, hummocky cross-bedding shows divergent palaeocurrents suggesting movement in part by deep-water waves. The beds are too coarse for antidune formation and the conglomerate to sand hummocks indicate decelerating flow. There are no nearby large objects to deflect turbidity currents to form divergent flows. We consider that the hummocky cross-stratification, like that in shallow water, was formed by interfering waves. That such coarse, tabular conglomerates affected by wave action occur over extensive areas across deep submarine fan environments, suggests deposition by high-velocity seaward-moving debris and grain flows followed by reworking by waves large enough to redistribute coarse sediment in deep water. The only waves large enough are those of giant tsunami. Petrology and geochemistry show no impact or explosive volcanic constituents in the finer units and the waves involved are too large for generation directly by submarine fault displacements. We suggest that the top Guwayza conglomerates were deposited by very large submarine slides which were then reworked by the tsunami generated by them. Such contemporary massive slope failure deposits are present on the adjacent slope and shelf margin.

Fine-grained sediments are usually interpreted as accumulating slowly in tranquil environments. However this report of extensive mudflows in the Upper Cretaceous of Madagascar, bearing abundant and well-preserved fossil vertebrates, reminds us that fine-grained sediments can be rapidly deposited.

Rogers R. R., ‘Fine-grained debris flows and extraordinary vertebrate burials in the Late Cretaceous of Madagascar’, Geology 2005;33(4):297-300.

Abstract. Vertebrate fossils are remarkably abundant and exceptionally well preserved within the Upper Cretaceous Maevarano Formation of northwestern Madagascar. The vast majority of these fossils, including all of the currently known bone beds, are entombed within deposits of fine-grained cohesive debris flows. These deposits are typically massive and are characterized by very poor sorting and a significant montmorillonite-dominated silt-clay (mud) fraction ranging from 17% to 46% by weight. Deposition is attributed to recurrent exceptional rainfall events that prompted erosion and flooded ancient channel belts with sediment-laden flows. These extraordinary burial events shielded vertebrate remains from destructive surface processes and also afforded protection for soft tissues. Taphonomic attributes of associated bone concentrations suggest that debris flows had limited transport potential and generally entombed subaerially exposed bone assemblages. The remarkable and recurrent association of bone beds and debris-flow deposits likely reflects marked seasonality in this Late Cretaceous terrestrial ecosystem, with prolonged dry spells prompting mortality and subsequent rains setting debris flows in motion.

This report of dinosaur trackways in a marine limestone will be of interest to those developing catastrophist models of Earth history. The two reported track sites are located near the village of Coisia in the French Jura. Both exposures are subvertical bedding planes showing sauropod footprints impressed in a Jurassic (Tithonian) limestone referred to the 'Couches du Chailley' Formation. The Couches du Chailley are bioturbated by Thalassinoides burrows and have yielded ammonites, gastropods, bivalves, algae and foraminifers. Conventionally they represent a subtidal environment such as a lagoon separated from the open sea by a coral reef. The dinosaur footprints are referred to the ichnogenus Parabrontopodus, attributed to sauropods or diplodocoids.These animals evidently left the tracks on a surface temporarily exposed between marine incursions.

Le Loeuff J., Gourrat C., Landry P., Hautier L., Liard R., Souillat C., Buffetaut E., Enay R., ‘A Late Jurassic sauropod tracksite from Southern Jura (France)’, Comptes Rendus Palevol 2006;5(5):705-709.

Abstract. The discovery of sauropod trackways in the Late Jurassic (Tithonian) of the Jura department (eastern France) is reported. More than 170 footprints (pes and manus prints) comprise at least nine trackways. The footprints are referred to the ichnogenus Parabrontopodus, characterized by a narrow-gauge trackway. The locality of Coisia is the most important sauropod tracksite in France.

Basaltic magmas from southern Patagonia have brought to the surface xenoliths containing olivine grains with rims that are depleted in hydrogen relative to the central core. The hydrogen profiles represent a dehydration process having occurred during ascent in the host magma. Demouchy et al (2006) have used experimental hydrogen diffusion data to fit the observed profiles, constraining the xenolith’s ascent rate. Surprisingly, some of these xenoliths appear to have reached the surface from 60-70 km depth within several hours.

Demouchy S, Jacobsen SD, Gaillard F, Stern CR, ‘Rapid magma ascent recorded by water diffusion profiles in mantle olivine’, Geology 2006;34(6):429-432.

Abstract: Mechanisms and rates of magma ascent play a critical role in eruption dynamics but remain poorly constrained phenomena. Water, dissolved in mantle minerals as hydrogen and partitioned into the magma during ascent, may provide clues to quantifying magma ascent rates prior to eruption. We determined the dehydration profiles in olivine crystals from peridotite mantle xenoliths within the Pali-Aike alkali basalt from Patagonia, Chile. The results demonstrate that the amount of water stored in the uppermost mantle has likely been underestimated due to water loss during transport. Using experimental diffusion data for hydrogen, we estimate that the xenoliths reached the surface from 60-70 km depth in several hours, a surprisingly rapid rise comparable to ascent rates for kimberlite magmas.

The latest edition of the Journal of Creation (formerly the TJ), published by Answers in Genesis, includes a forum on whether the Green River Formation (Eocene) was deposited during or after the Flood. Michael Oard argues the case for Flood deposition and John Whitmore argues for a post-Flood lacustrine model. These papers are currently not available on-line but here are the citations with abstracts. For what it’s worth, I’m with Whitmore!

Journal of Creation Editors, ‘Introduction to the Forum’, Journal of Creation 2006;20(1):45.

Oard M.J., Whitmore J.H., ‘The Green River Formation of the west-central United States: Flood or post-Flood?’, Journal of Creation 2006;20(1):46-49.

Abstract. Many creationists believe the Genesis Flood was responsible for the bulk of sedimentary rocks and fossils. However, disagreements often arise in trying to determine where the Flood/post-Flood boundary should be placed in the stratigraphic record. This forum is a friendly exchange between two young-earth creationists who hold differing views on the origin of the Green River Formation (GRF). The authors have examined the rocks in the field together. Mike Oard will defend the thesis that the GRF was deposited in the Flood and John Whitmore will defend the thesis that it is a post-Flood lacustrine (lake) deposit. This paper outlines the geological setting of the GRF.

Oard M.J., ‘The case for Flood deposition of the Green River Formation’, Journal of Creation 2006;20(1):50-54.

Abstract. The Green River Formation (GRF) is a controversial formation within creationist earth science. Evolutionary geologists see the GRF as a sequence of about six million varves deposited with other associated formations over a few tens of millions of years of geological time. Furthermore, these geologists also ‘find’ Milankovitch and sunspot cycles in the ‘varves’. A number of creation geologists have found evidence that has convinced them the GRF formed in a post-Flood lake. The several times I have examined the GRF from a geomorphological point of view, I have come to the conclusion that it was formed during the Flood.

Whitmore J.H., ‘The Green River Formation: a large post-Flood lake system’, Journal of Creation 2006;20(1):55-63.

Abstract. Evidence from lithology, sedimentology, paleontology, ecology, taphonomy, geochemistry and structural geology suggests the Green River Formation (GRF) was a large lake system. Certain features – such as multiple horizons of exploded fish, disarticulated fish and stromatolites – suggest the passage of more than the one year of time allowed for by the Genesis Flood. Since these deposits have multiple lacustrine characteristics, are relatively undeformed compared to the underlying basins on which they rest and since the GRF is near the top of the geologic rock record, it is argued that the GRF represents a post-Flood lacustrine deposit.

Oard M.J., ‘Response to the post-Flood lake model for the Green River Formation’, Journal of Creation 2006;20(1):64-71.

Abstract. Lake paleoenvironmental signatures, as discussed by John Whitmore, are equivocal and thus cannot be considered as valuable as the geomorphological evidences. The exploded fish and caddis fly burrows are challenging to a Flood interpretation, however, other features of the fossil fish and caddis fly burrows are anomalous for a post-Flood lake. An early Flood timing can explain many of the features interpreted to be from a post-Flood setting, such as bird and mammal tracks, raindrop impressions, and mudcracks. Furthermore a case can be made for the inorganic deposition of ‘stromatolites’, and ‘evaporites’ claimed in the Green River Formation (GRF) have anomalous features for a post-Flood lake. A Flood model can explain the deposition and features of the GRF.

Whitmore J.H., ‘The geologic setting of the Green River Formation’, Journal of Creation 2006;20(1):72-78.

Abstract. Further evidence is presented that the Green River Formation (GRF) was deposited after the Flood following the tectonic uplift of Psalm 104:8. A shift from continental-wide to regional sedimentation patterns within local basins makes this clear. Additional evidence suggests the GRF was deposited in a warm lacustrine ecosystem over a period of hundreds of years, suggesting the need to re-evaluate post-Flood climate models. Sedimentological, stratigraphic and structural evidence suggests pediments, developed on GRF basin fills, could not have formed until well after the Flood. For now, creationists should abandon the use of paleontological criteria (index fossils) in defining the post-Flood boundary and focus on sedimentological and stratigraphic criteria instead.

Oard M.J., ‘Geomorphology indicates the GRF was deposited in the Flood’, Journal of Creation 2006;20(1):79-80.

Abstract. Many aspects of geomorphology indicate that the Green River Formation (GRF) was deposited during the Flood. The massive deposition and erosion of the GRF immediately suggests the Flood catastrophe and not post-Flood processes. Pediments and the long-distance spread of well-rounded quartzites also points to the Flood. Furthermore, there are many climatic problems if the GRF and associated formations were post-Flood. Based on multiple criteria, it is believed that the Flood/post-Flood boundary is in the ‘late Cenozoic’ over the western [sic – USA?].

Whitmore J.H., ‘Difficulties with a Flood model for the Green River Formation’, Journal of Creation 2006;20(1):81-85.

Abstract. Some problems, though not insurmountable, exist with a lake model for the origin of the Green River Formation (GRF). However, critical evaluation of Oard’s Flood model shows it simply is not supported by field observations. His Flood model raises far more questions than it answers. Instead, the data clearly indicate the GRF was deposited within lakes, after the Flood.

A paper in the latest issue of Geology presents a new model for the emplacement of the Heart Mountain detachment, one of the most spectacular and puzzling gravity slide features on the surface of the Earth. Part of its mystery is its massive size (over 3400 km2) and the low-angle surface (~2°) on which it moved. Aharonov and Anders (2006) suggest that the extensive dyke network associated with the Eocene Absaroka Volcanics heated trapped waters near its base, resulting in overpressuring sufficient to initiate the catastrophic sliding that traversed more than 45 km.

Aharonov E., Anders M.H., ‘Hot water: a solution to the Heart Mountain detachment problem?’, Geology 2006;34(3):165-168.

Abstract. The Heart Mountain block slide of northwestern Wyoming and southwestern Montana is one of the largest slides known to have occurred in Earth’s history. This early Eocene block slide covered an area of over 3400 km2 and moved a minimum of 45 km across open terrain. The initial 2- to 4-km-thick Heart Mountain block slide moved on a slope of about 2°, detaching for half its length on a nondescript bedding plane in the Ordovician Big Horn Dolomite (BHD). Given our current understanding of fundamental mechanics, such a great mass of rock should not have begun sliding on such a gentle slope without some special condition. Here we suggest that a special condition existed during the interval between extensive upper-plate dike injections and the initial movement phase. In our model, the dike injections increased horizontal stresses and heated the surrounding layers. Both the increased stresses and the heat input elevated fluid pressure of water trapped within the BHD. In addition, vertical hydrofracturing was retarded as horizontal stress approached vertical, thus allowing a critical buildup of fluid pressure. Fluid overpressuring is a mechanism that can overcome the mechanical problem of initiating movement on a low-angle surface. Moreover, this mechanism explains the observed fluidized features found along the basal contact of the slide block as well as the observed lack of deformation in the lower plate.