Tuesday, March 16, 1999 POSTER SESSION I 7:00 p.m. UHCL

Impacts I

Takayama H. Tada R. Matsui T. Iturralde-Vinent M. A. Oji T. Tajika E. Kiyokawa S. Garciaanmd D. Okada H. Hasegawa T. Toyoda K. Origin of a Giant Event Deposit in Northwestern Cuba and Its Relation to K/T Boundary Impact [#1534] We investigated the Penalver Formation in northwestern Cuba, which is a <180 m thick, normal-graded calcareous clastic deposit. This formation must have been formed by a grain flow and huge tsunami waves caused by the K/T boundary impact.

Kiyokawa S. Tada R. Matsui T. Tajika E. Takayama H. Iturralde-Vinent M. R. Extraordinary Thick K/T Boundary Sequence; Cacarajicara Formation, Western Cuba [#1577] Cacarajicara Formation of western Cuba is the thickest K/T boundary sequence in the world. It is an upward- fining carbonate clastics, at least 300m in thickness. It might be a distal part of the ejector blanket of Chicxulub or a giant tsunami deposit.

Ward S. N. Asphaug E. Impact Tsunami: A Probabilistic Hazard Assessment [#1475] We apply linear tsunami theory to the NEO flux to investigate the generation, propagation, and hazard of tsunami spawned by oceanic asteroid impacts.

Matsui T. Imamura F. Tajika E. Nakano Y. Fujisawa Y. K/T Impact Tsunami [#1527] Numerical simulation of generation and propagation of the tsunami caused by the impact at the K/T boundary predicts that unusually gigantic tsunami attacked the coast of the Gulf of Mexico and the tsunami further propagated worldwide.

Nakamura Y. Christeson G. L. Buffler R. T. Morgan J. Warner M. Chicxulub Working Group Structure of the Chicxulub Impact Crater as Determined from Large-Offset Onshore-Offshore Seismic Data [#1288] Onshore-offshore seismic data over the Chicxulub impact crater revealed for the first time its deep structure. Major features include a central basement uplift and inward-dipping low-angle faults well outside the collapsed transient cavity.

Poag C. W. Secondary Craters from the Chesapeake Bay Impact [#1047] I document 23 secondary craters on two seismic reflection profiles north of the Chesapeake Bay primary crater (85-km-diameter). Seismostratigraphic analysis is calibrated with lithostratigraphy and biostratigraphy from nearby outcrops and bore holes.

Plescia J. B. Mulkarra , South Australia: A Complex Impact Structure [#1889] The Mulkarra impact structure in South Australia is interpreted as a having a diameter of ~20 km with a 9 km central pit or peak ring. This interpretation differs from that of Flynn (1988) who interpreted it as a simple 9 km bowl shaped crater.

Henkel H. Reimold W. U. Magnetic Model of the Central Uplift of the Vredefort Impact Structure [#1336] The negative magnetic anomalies occurring within the area of the central uplift of the Vredefort impact structure have been analyzed. The final model shows the extent of post-impact thermal re-magnetization and reveals structures related to the collapse of the central rise. Popov Y. Pohl J. Romushkevich R. Geothermal Investigations of the Ries Impact Structure [#1623] Thermal conductivity measurements of the 1206 m Ries 1973 drill core characterize and differentiate impact formations. From temperature gradients and the new conductivity data, inferences about heat flow and fluid movements can be drawn.

Pohl J. Geiss E. Investigations of the Ries Crater Ejecta Using a Digital Geological Map, DEM and GIS [#1531] A digital edition of the Ries crater geological map allows, together with digital elevation data, a new investigation of the statistical geological and morphological characteristics of the ejecta and their radial and azimuthal distribution.

Herkenhoff K. E. Giegengack R. Kriens B. J. Louie J. N. Omar G. I. Plescia J. B. Shoemaker E. M. Geological and Geophysical Studies of the Upheaval Dome Impact Structure, Utah [#1932] Detailed geologic mapping and geophysical data indicate that Upheaval Dome in Canyonlands National Park (southeastern Utah) originated by collapse of a transient cavity formed by impact, not by salt diapirism as previously proposed.

Kenkmann T. Ivanov B. A. Low-Angle Faulting in the Basement of Complex Impact Craters: Numerical Modelling and Field Observations in the Rochechouart Structure, France [#1544] Low-angle normal faults generate during crater modification in acoustically-fluidized rocks. Faulting is a result of an impact-induced rheological stratification of the crater floor and a passive rotation due to the uplift of the central peak.

Buchanan P. C. Koeberl C. Reimold W. U. Petrogenetic Modeling of the Dullstroom Formation, South Africa [#1290] The Dullstroom Formation was the first phase of a magmatic episode culminating in the formation of the Bushveld Complex. This study models available geochemical data to determine whether impact or endogenic terrestrial processes were responsible.

Hough R. M. Vishnevsky S. Abbott J. I. Pal’chik N. Raitala J. Gilmour I. New Data on the Nature of Impact Diamonds from the Lappajärvi Impact Structure, Finland [#1571] New data is presented on the characteristics of impact diamonds from the Lappajärvi impact structure, Finland.

Wolbach W. S. Widicus S. French B. M. Carbon-bearing from the Gardnos Impact Structure, Norway: No Evidence for Soot [#1043] To test the idea that combustion of the impactor or carbon-bearing rocks could have occurred during the impact that produced the Gardnos crater, we searched for soot in Gardnos impactites and related rocks. No detectable soot is observed in any of these Gardnos samples.

King D. T.Jr. Neathery T. L. Petruny L. W. Facies Within the Wetumpka Impact-Crater Fill, Alabama [#1634] This paper summarizes initial findings from drilling two 190-m deep holes within the Late Cretaceous Wetumpka impact crater, Alabama. Five intercalated impactite facies from the crater fill unit are described: sands; sandy and cataclastic diamictites; ; and blocks.

Komatsu G. Olsen J. W. Baker V. R. Field Observation of a Possible Impact Structure (Tsenkher Structure) in Southern Mongolia [#1041] In 1998 summer, we visited the Tsenkher Structure, a possible impact structure in southern Mongolia. The structure’s rim to rim diameter is 3.6 km, and a raised outer rim was observed. Prehistoric stone artifacts were found near the structure. Master S. Diallo D. P. Kande S. Wade S. The Velingara Ring Structure in Haute Casamance, Senegal: A Possible Large Buried Impact Crater [#1926] A new 48 km-diameter postulated impact crater, the Velingara structure, discovered on satellite images (centred on 14°7'40" W, 13°02'13.2" N, in Senegal), is developed in Mid-Eocene sediments, has a central uplift of metamorphic basement, and is buried by Neocene rocks.

Arday A(t). Bérczi Sz. Don Gy. Lukács B. Preliminary Report of Szilvágy-Patkó (Horseshoe): A New (Possible) Impact Crater Remnant in Hungary [#1384] In the last autumn during aerial photographing a central symmetric form was found 250 km SW from Budapest, in Hungary. We consider it to be a crater remnant, it is 500 m diameter and 25 m deep, and its southern wall is missing. Yet no transformed matter proves its origin.