1982LPSC...12.1623V in Abstract-The diagenetic discontinuous to breccia from and the than near facilitated cavity the well formed. cratered Because Snowball, explosion tures roborate rim vestigations. and (Roddy, cratering into hensive the meteorite possible accurate, carbonate aid are cratering compared target 1972 Eniwetok water-saturated The the Cactus crater Melosh needed effect mixing, deformation in the in log the Seismological autochthonous the and such following lining. the © lens, formulating characteristics. purpose Comparisons crater. data, carbonate observation details sedimentary analyses 1976), floor, of Lunar by the a detailed transition center. experiments excavation Crater, of crater) Shoemaker, Bingham Atoll. with sediments. as the craters, in their if chemical ftuidization involves horizon The target detailed observed Meteorite it folded Beneath order dynamic maximum conclusions: provide of and theoretically exists, of carbonate The It stratified and Laboratory, medium. in the Cactus structural description of Structural Joana that this model is as properties Planetary a between to breccia which situ offer excavation structure explosion high and ring lithologies the one impact rigorous and As object has rebound a of allow the using Secondly, large evidence 1963). study impact depth stratigraphic brecciation crater, for the faulted an velocity Crater a This rock faults of transition nature, appears material modification favorable Proc. Vizgirda maximum Cactus lenses dynamic addition California observations carbonate a and Institute the scale of of colored, induced is is of on of Explosion numerical crater strength of Printed process, theoretical Lunar this Cactus craters inferred this two-fold. (e.g., structure (with central an the smallest of observationally injection Eniwetok crater INTRODUCTION sedimentary detailed to and inside transition phenomena. study interval (e.g., Planet. and similar explosion in excavation rebound, tracer. having thickness be study, to the rock. Institute circumstances • Decaturville: saturation Crater, meteorite layered value deduced deformation. and as in depressed, Provided mixing morphologies. the mechanisms, United peaks Cactus assessment, Sci., Gosses craters of of is the are occurs First Atoll, treatment sedimentary observations Based 1623 cratering Outside dimensions located available occurs is provided 12B of strongly the a a Thomas modification States of of crater representative often from 105 rocks, maximum targets, (e.g., cavity Crater (1981), appears impact However, of is Cactus Technology, l Pacific and at by based on Bluff in m. of possibly m delineated gradually a 4 a all, the Cactus, Offield the America on the p. diameter shocked Sierra sketchy stratified in In A produced stratification of or, is data acting underwent by for craters and 1623-1639. to and Mg central and an (see to uncemented NASA Mg Runit cratering 20 rocks particular, strength Test crater 5 m at a of mechanism J. m be as calcite base, attempt unique these detailed sedimentary calcite over features least Madera; and this Meteor of Crater using the Pasadena, Ahrens as greater e.g., material below nuclear are a and Site a Island uplift Astrophysics display clays, targets, features. result target structural a Pohn, turbulent transition primarily of also such crater a transition interpretations 4.5 models. transition the Gault do stratigraphic nuclear qualitative as -1 sea is depth for of similar data explosion Crater; to ± Howard crater such to presented. of in high additional not media made a bar 0.5 California 4.5 1979), deformational level, Cactus Crater. partially form such the description are the crater et Laboratory at in m ± process, on as is is to permit as dependence craters. patterns 0.5 Data to 1/2 interval, al., cratering situ inferred to used North low observed those Milton structure for the and well a as crater and et synthesis Cactus', m crater present (especially tracer, variety 91125 1968) brecciation System excavation variables) al., cemented impact Mg is Snowball a as are compre fallback probably in to fallback inferred beneath Insight formed Pacific leading gamma for would calcite et 1972), event, radius which Using scale infer then as cor fea was the al., the in on an or of of a 1982LPSC...12.1623V It 1624 next Cactus diagenetic as calcite, decrease contains determined Fig. powder same compositional Mg scatter. o<{ 1846; ....-- ....._ u u w ~ 2.3 at of in algae. reflections x)CaC03(calcite) calcite) Chave organisms of of speeds the Atoll. and enriched Structural This discussed and our magnesian 6, earth's ± actual atoll, on exposed. (N.B.S. % two the these the 0.8 spacings concentrations certainly Runit (see it As upon from top 3.027 Runit MgC03 These 1980, the There to phenomenon in is by presence Results (1954) distinct under of were (excluding, magnesian weight typically core sea with variability inevitable cores, of occur calcite Fig. the surface 0.25° of samples in observed solution, exposure the certified A, metastably of core in Meteoric study pers. the level organisms calcite were not NASA this (hence levels does (Plummer samples a 2) for the such 13.8 respectively. considerable calcite on 20 % altered the between of Norelco X-ray + precipitation was observed. range associated rises, of following comm.) skeletal conditions no xMg++(aq) not per probably the and this 99.9% calcite that Astrophysics to in of occurs according of conditions is strongest stabilization to 20 MgC03 Cactus waters conducted samples compositions clearly MgC03 minute; exceed from diffraction 14.5 precipitate up detailed meteoric course, have low diagenetic and values) coral magnesian 14.15 correspond 29.43° diffractometer pure) to that material and between As weight Mg scatter section. represents Mackenzie, Crater According five percolate been concentrations with + ± illustrated 30 of calcite reef to 4 (containing from discussed content a is 0.35 xHC03-(aq). the was calcite reprecipitating determined Data the nature weight%. and minimum for waters, using the weight inorganically cores studies a boundary episodes calcite identified growth calcite %. in of (Fig. magnesian used to sharp any 29.81° biological Eniwetok weight following 29.48° System reflection Chave's through rock. powder may tropical skeletal MgC03 MgC03 of drilled to by 1974). of % in trans using is 1). as 1625 with less will of The dis this and and the the the the the (1) 20, is, by an be of In at % It in in 3 1982LPSC...12.1623V 1626 contours. Fig. of cores induced datum interval transectionally XRU cratered next Eniwetok 2. © section. are cores Map Lunar (Ristvet, (XC) limitations, displacements Dashed listed J. of and that Vizgirda and Atoll) Runit varying line uncratered 1981 in Planetary contained Table Island, occurs indicates magnesian pers. and beneath hydrologic (XRU) 1. Eniwetok T. Institute as comm.). position both All J. an 0 calcite Ahrens Cactus portions core abrupt high Atoll • of Differences regimes, 25 Provided sample diagenesis seismic • and Crater; of XRU-6 transition. (l SCALE METERS the l.30°N, LAGOON low 50 BACK island. depths refraction (48m) or, by these in 10.0 Mg on 10.7 XRU-4(44m) the l62. may these Depths Cactus Runit E REEF calcite. possibilities NASA are l5°E) . XPOE --- line. represent depth relative Crater 100 Island showing RUNIT to Astrophysics Therefore, SEISMIC this •XRU-2(51m) levels contour (and, will to transition positions permanent, -- the be may PREVAILING most ISLAND levels LINE Data mean within discussed be XRU-3 WIND of - - likely, are in System drillholes a low explosion • the difference sampling result (73m) in on water XRU - the all of in 1982LPSC...12.1623V tion observed Crater, observed levels Both that uppermost shown at depth intensity in Fig. most the similar spectra shallowest from peaks all analyzed centrations curve and Computer and tegrated samples section. evident curves, High transition to XC-1 will The X-ray 5 m levels -29.8° intensity, upper low 3. be increasing spectra observed © high prominent that Mg and in described in Portions spring for downward nature in Lunar addressed Core XRU-5 XRU-4 XRU-3 XRU-6 XRU-1 Mg pattern XC-1 of in Table and oiDepths (See XC-2, peak right below containing the powder with Fig. XC-1 according in calcite in XC-2 in and this and of XC-2 four calcite drawn four are of datum. the ape from samples consequently, XC-1 several and XC-1. 1. and while hand 3. Table of intensity graph: increasing low in of core low the -29.5° only of that, of core Runit at of XC-1 core plotted Peaks are in concentrations the (cc) Planetary the powder displacement in XC-2 diffraction corner. observed consistently the 5 Mg the these samples. and Mg Depth the The relative the that the to both 2 shallowest only material. first, high samples, peak XRU diagenetic samples and Calcite shallowest 28, for calcite of XC-1 calcite the ratios XC-2 next (see low discussion against X-ray significance samples. depth Note to of both low intensities the high XC-2 to respectively, Gaussian Institute Sample the cores to of High-to-Low 12.1±1.0 13.6±0.4 13.4± 11.1±0.5 13.7±1.3 method Mg Fig. and Transition low samples section. low spectra cores. Mg X-ray the progressive and Two the reproduced peak from diffractometer high the transition of the cores decreasing in available and calcite cores, depth were level, 0.6 mean 2), calculated calcite taken progressive Mg Mg depth That the the high noteworthy section. Mg with • intensities. diffraction described X-ray shallow markedly low curve of Provided XC~2 In drilled are core. calcite of empirical determined (m) calcite low and, of gradually peak and levels of Mg< depths depth outside are these to is Fig. XC-1 Mg XC-1 nature shown in sample high water observed. high 0 powder transition low fit low secondly, scans At present variation is fits Fig. inside are (above transition, 6, in calcite two increases parameters.) by differs samples present. features in Below peaks 15.4 Mg Mg the Mg Mg the these calibration and indicated of decreases to 4, of in the the for from features core. diffrac the calcite, calcite, show m, Cactus the crater. Fig. calcite calcite calcite in in NASA X-ray curve 20 XC-2 were the from were 20 next both con high and two are five the are m) in as in m 5. in a 4 Astrophysics (J) 0 0 z t;:J w u 0 (J) z o_ 0::: f- ::J 300 500 300 300 300 300 100 High Data j Low Mg System cc Mg ~13.6m ~\5.4m 11.8 12.Zm II.Im cc m 1982LPSC...12.1623V 1628 cite and Relative spectra. and (1965). of position below specific and ditional intensities 28.5° Sections baseline. provided sections and core I()= Fig. model: to XC-2 standard calcite and Mg where calcite D.21:1 troid where peak plitude, was simply Gaussian calcite core is tensity, high Sirnil~ly, 58 weight portion proportions standard Component A low m v' integrated can calcite comparison low D. the QUANTITATIVE is assumed low calibration 4. samples, © 7TC/D. and samples core was (all coincided and is A Mg 1(21:1) I( the is peak: f peak, therefore, peak, to Lunar % Powder be similarity technique was The the and _ Mg 28.82°±0.01°
the 300 300 500 500 300 500 100 100 100 NASA Astrophysics High High t t Mg Low Low cc t t -2a Mg 29° cc Data System -IOm -17m 20 m 28° 1982LPSC...12.1623V X-ray using Gaussian Due preceding samples and factory The calcite values explaining the and about discussed other coring the uncertainty level drilling, Ristvet sample essentially certainty, ling to and assessment. low was. between abrupt and discussed occurs Table Mg depth diagenesis low thus occur atolls duced radial Fig. Method the X-ray An In establish data location text. calcite to low 5. what uncertainties.) Mg positional Mg role anticipated conclusions an order Specifically, geologic DISCUSSION error diffraction of diffractometer the peak the initial in such fit difficulties geologic © Computer is CRATER island at used 1). lie et X-ray were boundary depth Mg curve 25 there calcite calcite Lunar paragraph to hydrologic extremely a expected. of below. quantitative these al., depths on the in process transition weight to in in Due altered limits in calcite lens the is of what as a the then previous fit calibration word 1978, calculating the evaluate observations is and this straight levels transects XC-1 supplementary variation peaks and data changes, parameters transition transition observations, Eniwetok, that drawn % a shaped to Cactus and between 1: presented information treated indicated the components geophysical in low and of 9 for 1.5 Planetary high STRUCTURE transition, Although spectra by could of In the boundary and of the standard regime is line tidal the crater values intensity observed undisturbed OF possible sections, elaboration meter high intensities curve) curve Mg subaerially caution this depth warranted. of configuration. it XC-2 cratering but as with not role are is would XRU 11 presented calcite variations of is and CACTUS meteoric the described in observed below Institute fits formation. listed require additional and be the sample, first in uncertainty and a these together were remain on to of to is a samples; low data and of Fig. slope cratering is each high obtained. the concerning needed. of the and vary correlation the cores arguments the described the necessary in transition 14 Mg on event situation calculated meteoric obtained. exposed the can standard are Due high 6. Table high sample. of greater, critical high above, rn a to during waters nature • samp in depth calcite. as fairly along satis with (See 1/86. It Provided high (see this say and low are not un Mg the As in At an to in to in to 2. is in >- 1- .... Table 2. X-Ray peak Gaussian fit parameters lmgh< 2> Weight% High<3> Sample A B c lmg1i+ ILow Mg calcite Calibration Samples (High/Low Mg Calcite; weight%) • 25/75 1.47 ± 0.12 3.37 ±0.18 7.55 ±0.06 2.92±0.09 0.14±0.03 44/56 3.67 ± 0.10 2.57 ± 0.15 7.65 ±0.09 3.16±0.11 0.37 ±0.03 65/35 4.81 ±0.10 2.46±0.11 3.91 ±0.09 3.30±0.14 0.62±0.03 88/12 6.20±0.10 2.55 ±0.15 1.58 ± 0.20 4.25 ±0.21 0.87 ± 0.03 XC-1 Samples (Depth; m) 11.1 3.95 ±0.35 2.51 ±0.55 0.48 ±0.22 1.67 ± 0.61 0.85 ±0.11 87± 10 11.8 6.31 ±0.18 2.44±0.23 2.75 ±0.20 3.65 ± 0.31 0.77±0.05 80±4 12.2 4.44 ±0.05 2.97 ±0.13 1.78 ±0.06 2.99±0.12 0.72±0.02 75±2 13.6±0.9 4.82 ±0.13 2.73 ±0.22 5.86±0.15 3.29±0.27 0.50±0.05 57±4 XC-2 Samples (Depth; m) 15.2±0.9 6.73 ± 0.38 2.26±0.49 1.65 ±0.44 5.34± 1.73 0.91 ±0.07 93±7 17.2±0.5 4.72± 0.27 2.00±0.34 5.48 ± 0.17 3.71 ±0.44 0.62±0.08 68±7 (l)Parameters A, B, C and Dare related (but not numerically equal) to high Mg calcite peak height, width, low Mg calcite peak height and width, resEectively. Gaussian fit model discussed in text. < Integrated peak intensities of (high Mg calcite)/(high Mg calcite+ low Mg calcite). <3lObtained comparing calculated intensity ratios with calibration curve. 1982LPSC...12.1623V constant (1974) units presented, both cores. illustrated relative proximity data. depression becomes changes into 4 however, According pressure (i.e., are from 2.5 XRU-1 unconformities sion The to m observed this beneath 5 m older are f- 0 I Q_ the w The E Fig. the respectively. vs. stratigraphic indicate were As Runit © to and 20 22 directly 10 Lunar 16 14 12 18 observed depth along area, 4 decay of elongated 6. 20 noted difficult. in are of that depths to than to at obtained Weight% XRU-3 downward Island and Fig. 5 m to Cactus. results cores these 0 in that consistent and in and any across be the rates in beneath displacement the 35 • 0 7, XRU-3; Note to at Table depressed and Planetary such drill cores determining Pressure first a m XRU-1 island xc but xc perimeter 10 core. the of Eniwetok high cross-section from of solution the the this pressure -1 -2 displacement locations. on high solution lateral d 1, the XC-1 XRU-1, Mg a 20 with smooth crater outline (depth)- the locations however, study, and similar Institute calcite, crater, of to beneath attenuation (i.e., and unconformities variations Atoll. opposite the low stratigraphic whether 4 30 decay unconformity cannot variation 4 WT Since shock to XC-2 and XC-2 of 2 displacement as and Mg circum- it to the Cactus to the • in Cactus determined is 40 considerations Provided the d- samples calcite 3 o/o the from be the order impossible metamorphic side or transition crater in were 3 in considerations • Structural determined. reef nature diagenetic not parallel HIGH In both north-west the Crater Crater 50 of depression are to correlative transition drilled addition, are (see downward the from XC-1 by is crest. cores accommodate v based of indicated noted level the 60 Mg to constructed crater), Fig. suggests to powder the ~ curve. study levels in trace suggest of NASA features According Nevertheless, the on of 7). in deeper a should Mg for CALCITE composition occurring 70 (Vizgirda with /~ line displacement XRU-1 by Couch Since the of a the X-ray in ~~ reef XRU-4. calcite Astrophysics possible sharp solid cratering Cactus calcite approximately the crater behavior be from theoretically 80 solution of no diffraction crest). to et is Mg and similar transition diagenetic beneath and single core with These al. depressed XRU the from available Crater cratering 90 (i.e., calcite open (1975) induced is unconformities depth of Data Ahrens, samples Ristvet argument in XC-1 spectra, and present relations stratigraphic circles, in the 100 these the reasonable 2 drastically ~ parallel transition) System transition data. and line evidence XC 1 to induced solution depres require crater. below et three 1980) core 1631 here with The just 3 are al. to m 1982LPSC...12.1623V 1632 from Characteristics fundamental observed observed Island, Mg lens. transitional relative sidered several fluidization Figs. Mixing material XC-1 which particle extent of decreased the previous brecciation approximately ciation lithology, sketched material Finally, As The First of Fig. peak calcite mixing calcite "excavation SEA © the If 2, the discussed drill the Lunar observed 7. of nor of conclusions and was as inside a 4 to high velocities excavated LEVEL.--r-~~-,----,.~,.,,~~~-r-~~~~~-r~ experienced data sentences cavity, Cross-section in in in ~ I fallback 0 f- and the E all, however, site, that with the J. belonging hole was displayed is likely Mg of samples Fig. mixing 40 30 to 50 cores 20 probably 10 reclassification Vizgirda and and the gradational the it 6), low the form in o a to of 15 depth. calcite was sufficient in expected 7. pattern since cavity". solution crater. Planetary suggests XC-1. fact occurred, Mg this drilled breccia and previous originally imparted during are, -- Limestone - may thickness regarding from collared I of our to calcite 00 - by some through initiated that and ejection feature, layer - 20 The the the XC-1 Neither therefore, % unconformity of XC-1 have methods It outside Mg cores considering to m Limit Observed the that lens T. the Institute transition degree the class datum creating transitional the sections, XC-2 is Transitional after saturated in of completely high J. in Cactus calcite the of cratering transition occurred 4 m and the unambiguously by of is exists, transitional drilled Ahrens XC-1 Cactus extrapolated of and 1 m of the not mechanics Mg in is XRU-1 used material passage of material these crater would thick 2 boundary • simple mean Crater an the situ data lens or core expected crater. the excavation, Provided calcite and the it inside but inviscid, event to less. Craterz Mg at observations occurs first is boundary in homogenize of brecciation nature 0 low reflects conditions not XRU-4 define constructed samples competent XC-2 deeper limited % flat-floored Couch of Mg both travelling in calcite toward The This of content' Cactus "mixing water sample experienced this the allow resulting by to calcite crater in which readily of cores the drill-core gradual et though the the result is a transitional levels explosion-induced at the level. is al. the zone layer, consistent the Crater minimum its NASA under was on the radially rate is not hand coralline lines" (1975). formation. cratered layer and craters. up high mixed from consistent difference in the detection. (Two-fold not within center change XRU-3 found retrieved. at in sketched to such is locations, contrasts Astrophysics which basis specimen Note lo aids also to in situ which ejection, depressed the the area downward interval substance. limit manner As limestone, low Fig. a of a anywhere of the from brecciation cratering 105 340,000 present and finely vertical totally the depicted with between the Solution The the this Mg of 6 in apparent Instead, ,000 drastically the respectively. shock in are size diagenesis down Time was in high all in crater, Fig. the calcite o 5 m to 4 Data stratified turbulent inferred depths the and exaggeration.) situ both unconformit1es The low has high valid, at event, else and never (YBP) samples. structure the in 7 depression definition to front. least System and the outward brecciation turbulence Mg suggests been i.e., Fig. cores low to transition depths depths central with on noted then in bulk mixing. ejected occurs. breccia lead all mixing calcite partial at Mg 7, Runit Brec After XC-2 con (see that The of low the the the of to of of at at in a a 1982LPSC...12.1623V levels depths from extent, inaccurate, central Island. vicinity. may homogeneities, portion structure simple crater error displacement lowest XRU the XC-1. uncemented 3.1 from On depression along carbonate earlier, approximately 20 to the the Apparent 50 unbleached first at approaches depth as Table vestigate ments, unbleached crater. origin cores ciation 1978) Mg 16 Seismic Seismic Paleontological the ± m m the we km/sec northeastern disturbance the second © calcite 1.5 produce solution below the the shock-induced is depth, are XRU-1 is would above in boreholes, end the shall Lunar 1. Lacking reef layer Such For in crater. however, of and and are m uplift. insufficient basis consistent center the In This limited the can the rock investigations the island, below seismic of extent velocities did with and example, margin, foraminif layer, the shells see observed as in carbonate mixing an this represents the appear not and Cactus is the phenomenon and the unconformity, of center be fossil Rather, occur Two shown 15 datum. must Cactus appears 6 m cratered the observation is good in causing increasing first to ocean be the observed Planetary this, may refraction drawn. case, m XRU-4, four compatible of i.e., evidence of the with to structural velocities an and it an beneath brecciation to depths) Crater other Ristvet datum. era the first of this evidence beneath unconformity, determined geologic the is alter next to and in be approximately On the sediments, isolated the margin Crater seismic 4 m to be unconsolidated decreased the the area. the conducted inferred shells encrusting Fig. second As decrease under be where the seismic be Institute pattern layer the of possibilities, depressed the section, observation depth, for cores would line crater observed (Ristvet Outside depiction et correlative investigated the between mentioned depressed with classification Cactus Since 7, basis cratering of controls, are (see is al. cores. seismic conclusion the case. beneath the layers or closest two of the possibility crater (Ristvet unclear in appears are (1978) these the interpretation is velocities be observed profile. than reflecting first on overestimated of • consistently Fig. the unconsolidated foraminifera, this are transition the Cactus, the solution Crater. et 550 Provided analogous maximum not the Runit beneath this Nevertheless, of are evidence, and supratidal induced observation observed to 3 m and large al. 2). at that with in presence in describe namely layers m refraction before high in to precisely et the regarding the ambiguous. and The a particular Based Structural the long second cannot distinguished 1978) crater. in together Island involves the thicken al., unbleached that greater distance the a the unconformities, by crater was to the Cactus Cactus variation the beginning to second brecciation. excavation consistently seismic from 1978) extent any depth low the in a Homotrema transitional Ristvet it of Mg by sediments supports on proximity the during The be of observed cable to third known. of XC-1 of profile is NASA the toward some at degrees is the Mg up firm this fracturing, these borehole conclusively calcite of study weakly co-existence Inhomogeneities that 2.4 a Cactus not Crater; floor depth any about uncertainties of layer, refraction existence is to complex shells calcite berm one-half layer Homotrema profile Project and et in km/sec of conclusions inhomogeneity not Astrophysics noted the the unconformities, 3 may speculations level limit Nevertheless, of Cactus, and The al. as of m. the this as transition of of layer vary 20 rubrum, as occurring 2 cemented located expected Cactus are the consisting of velocity a excavation evidence the cores down cores transition evidence transition (1978) this but m A and cementation. below symmetrical a be is above sharp velocities EXPOE upper whether morphology section, crater to of moderately complex profile found eliminated. below second crater. extent of of from occurs and no used lower geophysical a 2.0 and uniform both Crater concerning which south rubrum also diagenetic central Data do Cactus mixing. 16 depths, decrease between in the 60 carbonate involving km/sec radius in only in obtained sea 0.4 to m the (Ristvet of As sample of exist velocity structural bleached a situation cavity. m high respectively. recorded crater at suggest interface to the the System line beneath of indicate further km/sec level. weakly mentioned downward would margin in However, above The of cemented shallower depths thickness uplift; Crater evidence borehole outward cratered listed in and western parallel a as logs 20 results with break, Runit. crater depth Runit et along Pink, small brec layer from shal sedi 1633 This that that and and low one al., the the for in in (at be an its of of of of to to in a 1982LPSC...12.1623V 1634 60 the radiation process. patterns boreholes. excavation proximity Woolum, pattern, supports device. Central data. laboratory laboratory the rarefaction target, velocities why radiation the formation that velocity particles crater jection transition. and be and depth is layered In Material Suffield differences 2 As (HOB) despite device completely detonated media, empirical efficiency Co, m) The Gamma an an made shallower in target COMPARISONS order XC-2 explosion the © the 102 is attempt Cactus, experimental of observed excavation Lunar were one had Laboratory, Rh, As of the to (Alberta) clays, Because shallow observed therefore, are fell injected exhibiting is pattern 9 m second m1xmg levels 1974), were cores, (within correlation and of model logs at of J. measurements the As observed explain cavity wave the between being much between unconsolidated an 125 back reproduced ejected ground Vizgirda compared peak and 10 high to Sb craters, formed an water silts two approximately induced shock were distribution peak µ, were respectively) and in gain produced occurring high peak derived Planetary greater a and site 1 material, based accuracy into limits of at and m) explosive, the basically the Cactus is and explosions. McClellan explosion Cactus high the infilling level, deep at obtained XC-2. curves by a wave radiation 155 the recorded Snowball, and a intensity a the to penetration highest in broader deeper 1 to high based on silty lining Eu) Cactus in WITH result the (by the m, on corroborate intensity cavity the best high respective T. upon Crater Institute i.e., the sediments. respectively. to Fig. check and Lack from of competent of detonation the respectively a in nuclear occurred velocities sands. J. agree same relative 1 m for on depths to Air factor measured crater, comparison gamma Mg levels radiation zero peak. of 24 Cooper Ahrens The radiation Snowball at perspective reflection 8. and and basis corresponding the OTHER of the the may depths on Force most HOB. split calcite cratering Note several peaks material. well • samples Snowball 500 HOB, constitute Snowball device. excavation of dimensions gamma explosion Provided the both are This of formed There of after be to radiation from but spoon (1977), 36) of of with Base; radiation the Ristvet ton intensity The the of 16 the peak craters. gamma (see are nuclear data. produced of 500 (in depths whereas peaks the saturated yield interpretation CRATERS ± the nuclear of from The the two Some produced is TNT those well Mg the result consistently similarity 1.5 has terms samples by at sites this tons e.g., a the Cactus EXPOE a was propagated crater serves shock to cavity. thin of et observed of m small calcite the high growing observed the log, The 18 log levels explosive, peaks a in data of cratering hemisphere determined Cactus of of are that fission al. Fleischer the and only 105 not of to diameter NASA fallback coral this boreholes evidence Defense radiation latter, the TNT intensity formed. Crater wave were 20 to difference particle (1978) size is in m Other in 18 boreholes. originated transition observed. represent the speculated in AND further m also material is following crater the and 2 m kTon rock, products post-event size is Astrophysics in into and in substrate depths from efficiency measured described consistent delineation due sources. breccia in gamma of et also strength particles, presented from saturated, deeper 10.7 Research (16 A producing between levels motions. peaks substrate the relation CONCLUSIONS the XC-1 TNT cavity. al., 107 to elucidate in thin the travelled data. the m closest m Depths of propose As and the greater target, the sequence other, the for m lens. and 1975; free for radiation logs XC-2 materials equivalent than breccia (primarily fallback observed According (defined and by at anticipated, properties Data and same engulfed with neutrons heights In to in the Some of unconsolidated Cactus. Establishment, Cactus The the 19 similarities) Snowball surface Roddy It to of saturated the Fig. other addition, high of XC-2; Burnett the may radially a a forceful m System is two the XC-1, McClellan Mg the of maximum lens minimum the proposed observed cratering for and intensity as cratering 8. of well in of particle in explain nuclear events. Crater. due craters Cactus impact (1976), by calcite are These to of of Major crater crater these these XC-1 close three burst both (1 high high into and and was and the the the log the the on in to to to 1982LPSC...12.1623V volume/yield) and intensely nuclear with Snowball. could the sufficient nature of observed tively) ment, important Despite material sediments. shock-induced of important material those value considered collapse calculated be of p) existant), according depth breccia simple Applying Although motions and magnitude water the XC-2 Cactus. 4 © Fig. log nanocuries XC-1 al., at probably allowing of to to of Lunar a terrestrial ordered explosive critical the below lens can 1978. data these transient the strength 8. 5 m shattered I ()_ f--- w 0 5 in integrity away E the Cactus feasibility some Although to being (g and occurred Differences here. SL 20 40 30 for 50 Cactus 10 Snowball the the information occur; bottom this A is of (solid and and (Datum two have is - XC-2 it brecciation, resolution the per differences, not from the parameter distinct uplift. !-----< Bingham comparisons two movements 50 target Using !Om moved '\, model, Planetary core craters source crater of central the Crater gram, and line) acceleration '\, and been have central times dimensionless cores; intensely beneath of argument is " the types the Crater rim The mean in suggest a the can saturation, "- mixed, and toward respectively. central depth, cross-section for been measured water-saturated central on shocked for is of shock '- peaks. greater units plastic determining Institute position breccia peak rock the of be laboratory 1: the low quantitative mass site the terrestrial craters beneath folded, between 3 mapped. for substrates and, for mapped. turbulent coral H, of the (Dence water compression making formation peak crater (Wilson, two peak. Furthermore, model for movements the these gravity). coral of strength and lens for center • had of Figure (no with rock 20 a level.) Provided the measured craters description structure, Snowball. floor: a Numbered the the these Thus, can high two crater meteorite et m, up visually vertical Cactus, Kcps: nC1/g: of material. treatment coral variety 123456 brecciation clay may 1927, HOB and is al., becomes requires this a analogy Interestingly, Structural excavated be Melosh parameter, data compiled explosive the maximum properties, craters significant during are --- - up density, 1977). and ascertained, by size differences be total p. central exaggeration) and sets of distinguishable as top with to the 58-59). It of responsible According markers craters similar of silt Kcps nCi/g: a water-saturated and speculated, of gamma (1981) 1234'56 form less are -- Cactus layer volume appears, from cratering, NASA Determining and larger and crater study an cavity p, Snowball structure, relative -- beds - pgH/c, Bingham in differences shape. or coherent yield of The --- the mixing data uplift moved Cactus Mg Observed kilocounts Lower is in in gives the activity used Astrophysics in value, 2.4g/cc as of showing structure in characteristics calcite the central often / to yield is many the presented stresses for therefore, Cactus a depth indicate is this to limit also There units this particularly of in complex yield to however, some mode compared radially required crater amount can but both a than lens the (dashed stress, of the central clays, incomplete (from 8.5 Cactus gamma exist per high peak. has respects, to diameter to model, trans1t1onal been target the stress Crater be varying of is boundary in indication m, Snowball of the two the second Data a energy Ristvet in outward, while the limiting potential that crater. therefore, measured or drawn. comparable disruption line) Samples appears ( is before present, central mount extent y) silt serves discrete of to dependence. the of System distribution a difficult same evident well and following Snowball the the behavior. minimum for ~ and (or size et density ratio experi 1 case Where of retain crater of peak, bar as (rela order to from then, most 1635 they non bulk clay may sets and are the the for be an in to of is is 1982LPSC...12.1623V ratio palinspastic (Dence complex loose 1636 therefore, to had rock. subsurface calculated displacement of depression culations, general crater Robertson Meteor to Piekutowski peaks, breccia, structure, sion (Yurk (Shoemaker, cavity Cactus, either speculated on depression Grieve, and craters, Crater (Shoemaker, location identified interpretations Brent meteorite melt rocks example on et model. shocked 1968; Downward The The In Grieve d- al. the have the the a Floran, beneath Vizgirda 3 distribution of In • similar Fredriksson (1968), saturated cannot are and © et y theorized rock with one These y boundary. The observations. Crater basis et proposed and complex and 1977). 1: Lunar have Manicouagan, ray undergone and structures, log al., in et fragments downward is concentrated 4 and there Lonar J. depression al., of in data, located of inf reconstruction complex section al. more a extended intensity evidence, or the 1978). depth simple which 1975), 1963). Vizgirda be among are pulverized rates displacement and rocks of terms Boltysh, been erred (Shoemaker, Grieve distinct and 1977), Considering stemming (1977), 1: sand, drawn. Pohl thin speculative is analogy consistent electron craters, Lake Ahrens 5 a compatible This et to Planetary are near Melt These however, some beneath 1963) common beneath experimental utilized (Dence observed and sequence and downward others, al., displacement craters. of Thin (1 diameter logs, (1977) beneath even for and et Piekutowski an compatible are on central a Craters, The pattern m in the post-flow rock highly al. 1973). the layers between (1980), rocks 20-25 and analogy a from fallback the evidence, two interpreted T. spin or of the discussed has mere with those (1977) 1963). crater interesting et speculate In the Institute the saturated the nature depth The J. cratering with less) the the Gasses in in of basis Cactus. ratio. top al., layers At shocked a uplift. in km Ahrens not resonance and is are formed Cactus central crater an reasonable uncertainty simple events both 20 impact laboratory extensive lower Sierra between the On which Boltysh with that Meteor of surface speculate breccia similar fallback stratigraphic 1977). and to (1977) attenuation diameter actually m. of of detected The inward which in • 4 Bluff as of ring the that diameter target simple These model fact impact of Its model occurred Provided to those the basal peak "unit" craters and target in Crater Madera the craters apparent highly offer complex Using basis 5 m lateral Crater, observed lenses, depression to surrounding and and Cactus detected granitic (Milton remains, melt previous breccia attenuation eventually material material been that scale motions. structure in (Brenan at inferred materials, for the portions laboratory and attenuation is rock melt the rate of simple sufficient of in ratio shocked observations has by two the sheets coordinates. geologic consistent and at extent, the both relative formed distribution melt 1: observed study and attenuation crystalline complex other structures. the et gneiss of Brent, lens are distributions 5 been however, downward section, shock estimate lining transient Gosses distinct motions of and al., ratio for et (depth)- craters NASA At simple types in of the described was concentrated rates. dies lend at al., thus, these at of material stratigraphic 1972). studies, to clearly pre-Cambrian observations simple approximately entirely the the rates, and a central the for with Cactus the metamorphism; explosive detected the beneath structures, 1975). simple Astrophysics revealed Bluff of out intervals significant craters and during cannot are According that remains excavated 5 rate of cavity excavation Red the in basalt, craters · hypothesized 7 displacement extent structures. attenuation firm is in craters demonstrated at at melts displacement have in consistent true particularly peak sedimentary estimated structures calculated arguments, Stratigraphic is simple complex Wing crater the any greater in sedimentary at may be of in conclusions two respectively, craters ambiguous, is of control, cavity beneath and not similar typically such only crystalline or the agreement (Robertson 50% justified. Cactus support cavity speculative. autochthonous Data to simple cavity be Creek high in and Some been of geophysical Ries this rates amounts model craters, excavation depth, warranted. 1 shortening for suggests crystalline as of with beneath formed System however, positions intensely those by borehole intensity rock. complex such the beneath Cactus, (Dence, excava- depres (Grieve Meteor craters Cactus appear rate clearly Crater buried to rocks, of Based of about Gault and their rock with melt ring cal and the for d- the for At as of of in A is a a a 2 1982LPSC...12.1623V displacement beneath a limited the the the tion high Summarizing calcite intensely transition the disordering carbonate observation Fig. may peaks particularly in assumes a complex investigations approximates impact of mechanism be simple simple and Fig. model modification excavation discussed preference single 105 situ Grieve confirmed. resultant excavation modification high complex © stage, velocity have 9), 9. m in represents Lunar brecciation craters) and craters to Sketches crater excavation diameter a such velocities craters, in the iodrd central disordered of in rock. process produced a et for commonly the y mechanisms. does in the simple, suggests maximum the true and injection the y log craters. al. that a The (Schmidt suggests text. example, cavity observations serve the rebound log hydrodynamic Such limit mechanism XC-1 not (1977), such data, key Planetary crater (after depicting complex and of difference and data, Cactus model craters. the seem to observations the is a This of the that as core, involves of mixing invoked model Melosh, thickness Dashed sequence low an depth and support of deduced Cactus agree region central inferred transient the structure. to a can autochthonous Institute same essential crater cratering two viscosities Holsapple, acting and rebound hs observations Thus, peak. for (see have remainder between to is rebound line closely be 1981). "fluidized" both a modification central Cactus uplifts. envisioned diameter suggestion its possible of of on with basic to applicable e.g., in taken and crater; at As Maximum • close events difference 1 ejection the Reasons be SUMMARY the event, Cactus Provided mechanism m. this with Crater interpretations, 4 evidenced of theory contention 1981). If peak. Pike, to analogous rebound place to basis The similarity ratio during origin the rebound, the crater form ratio is that Structural has 5 as then are for to is consistent m of means The depth intensely depth excavation to 1980) in a by in is of less both been and of a some and described very explain the at 1: the the (Fig. lining in impact the Melosh of to central 5. and to clear. Cactus the to of a the central NASA and simple for transient proffered the turbulent The the of fallback study observed the Cactus the diameter 9) CRATER not shocked with to 1: the various orderly Grieve complex basal experimental melt Centripetal majority 3 process, rather transition by uplift the (1981) excavation Astrophysics sliding, value Crater and CENTRIPETAL uplift of highly the Grieve Crater transient crater breccia distribution mechanism, Cactus on MODIFICATION and complex ratio et crater crater and morphologic and, REBOUND high than Bingham commonly of the of al. craters, as was (specifically, shocked upper trend can Cactus geometry possible et sliding the probably, of model, cavity to deduced basis lens, centripetal Crater excavation indeed diameter crater Data explosive al. SLIDING 1: be low breccia craters. in melt 5 plastic Evidence facilitated in if produces of described material MODELS Crater. (depicted is would, System observed XC-2, that features Mg it downward floor. terrestrial, the terrestrial 20 of from layers exists, fluidized the infilling closely m, Cactus is, calcite sliding simple model model active crater such 1637 This This thus that two and and Mg for by an as of in in in is 1982LPSC...12.1623V 1638 Crater dynamic crater rebound shock-affected based B~ggild and caution, cratering Chave guidelines gories. Burnett Brenan Cooper Chave Couch quantitative research Acknowledgments-Discussions Gault Geological Dence Dence Fleischer Grieve Grieve Land Melosh Howard Milton Fredriksson Neumann p. events. 235-326. McKenzie Operations characteristics Mono, Pepin, AFWL-TR-75-216. Proc. Applications. Geo!. crater interrelations R. the to Some E. Baltimore. Bull. 1199-1207. Shock Shock 11-44. may central C. B. © L. occurrence D. K. K. on R. with M. D. M. R. Mar. Lunar R. 62, E., R. modification, H.J. H. Merrill, Lunar D. 0. K. in The S. Metamorphism E., and of Baltimore. was Metamorphism since model J., In F., E. rebound R. E. A. Cactus A. have R. R., mechanisms and L., Van basalt. Pergamon, F. A. S. (1%7) 266--283. in A., B. J. the peaks K., Quaide many Barlow (1952) County, Impact (1954) Sci. C. Fetzer R. (1981) L., F., in (1968) evaluation supported and Jr. Grieve the detailed Vizgirda and Peterson Sci. (1930) F. Offield Planetary Univ. Son with the Dube eds.), (1%5) Eniwetok B. features carbonate been Dence and of Price of 15, (1977) Diagenesis and Science of formulation to Woolum Merrill, features Conf. Planetary A Aspects W. A J., mechanism impact B. J., unique Melosh Shock and basement 987-1035. 267 energy North lunar other R. A., solid Calif., The p. T. N.Y. schematic Processes C., produced and Floran Goter on L., P. M. of 791-814. A B. and observations W., A. under of pp. as Explosion 5th, Milton Sciences, observed Brett, of Atoll 180, B., shell and Natural Young eds.), craters. solution summary the melts. zoning R., L., D. Dakota, Natural medium. impact of F., well considerations. properties Berkeley. similar and of (1981), target E., T. p. Institute and R. and and the 862-864. Oberbeck S. and DNA and with basis During skeletal R., 2061-2074. of structure D. J. model Ristvet Wilshire p. of rather Pergamon, In as G. by (1974) J. at biogeochemistry formational Geol. Robertson Waler Materials J., Ahrens Brown theoretical California 247-275. between recent Cratering Robertson Smith and Wyom. Impact Materials at properties to A. (1978) of B. a Canadian modulate the contract and Clays, 605 of REFERENCES Project of maximum Cactus (1972) • Cactus) carbonates. explosion presented Ristvet of B., Lunar than explosion Soc. V. H. Provided R. crater of the same Balasundaram A. pp. carbonate H. a In Geol. Manicouagan Tremba and R. calcite Pergamon, N.Y. G. R., (B. the M. water-saturated Amer. P. Institute (D. such Gosses J. Impact centripetal Mg processes. (1968) (B. 001-79-C-0252. P. craters: EXPOE. (1972) have neutron cratering and Explosion Glikson transitions modification on M. B. processes. was (1975) (1975) mollusks. Assoc. J. B. cratering M. yield and of calcite (1977) J. by as French structures, crater E., here Roddy, Bull. J. sedimentation (1977) Impact counterparts Bluff formed, Structure Sediment. and magnesium, French of the those Melosh petrography N.Y. dolomite. The Walter capture Nuclear A. Air M. Earth stress J. 83, Technology, impact models. Cratering Explosion Cratering NASA will, impact Y., sliding. and Terrestrial morphologies, Danske phenomena study, S. Geophys. R. Force origin cratering between Application by 2795-2808. in Contribution and (1973) Manwaring D., have Sci. 0. carbonate are of N. of as Petrol. gravity. however, which Tracks hopefully, J. Astrophysics melt, structure, Sierra calcareons and Pepin, N. Weapons M. of a in -1 Bull. gratefully is Geol. in Using Vidensk. and processes: (D. comparable Lunar Cratering tracer Res. Harrington mechanics Short, Red M. Pasadena, terrestrial impact speculated Werdland basic bar 37, relevant Snowball Quebec J. structural J. 8, Madera, in 60, and Short, E. Roddy, 83, of Geophys. 914-930. Wing target 1-41. the should Lake, is No. for Solids: and Australia. Laboratory, A., eds.), 190-192. Selsk. marine contribute morphologic 2761-2771. a acknowledged. calculated structures: R. (D. as regolith Data Bingham Moss cratering 3615, Part to eds.), and serve V. Sound, Creek California B. Texas, India: interpreted impact R. yield may implications. p. J. (an proceed to meteor Principles (1975) Skr. Merrill, Res. 0. structures. Roddy, 87-99. organisms. System F. 2. Science Division p. involve explosion as Pepin, influence dynamics, An J., structure: stresses. as Bermuda. 9, Chemical Rep. In principal 169-184. for craters plastic to Drilling Sedmik model useful a impact impact 91125. Mono, pt. press. cate eds.), R. guide with from This 175, the No. the and and II, 0. of In In J. a 1982LPSC...12.1623V Offield Plummer Pohl Piekutowski Pike Ristvet Ristvet Robertson Roddy Vizgirda Silliman Schmidt Shoemaker Wilson Yurk Geo!. experiments. Merrill, to P. Lunar Weapons V. Cratering impact Geol. p. (abstract). Impact Pergamon, Houston. Comets Cosmochim. meteorite the J., 189-199. P. R. (1978) Y. T. D. © B. H. (1974) B. Stoffler Survey. J. Soc. dissolution B. and R. J. L. craters. Y., eds.), Lunar and W. J. (D. (1980) L., (1978) L., P. and (1846) E. Laboratory, Geologic (D. M. N. crater. (1976) Amer. Planetary In N.Y. A. and Tremba E. B. A Yeremenko M. Couch Explosion M. and Acta D., Prof. and J. Ahrens p. In Quaternary Lunar Terrain and Ceramics and J. Proc. Middlehurst (1963) Pohn Roddy, 67-102. On Gall Mackenzie Int. 6, High-explosive of Impact Holsapple (1977) 44, Paper and Grieve R. Planetary 928--929. the magnesian Science Geol. Lunar H., T. H. Rep. and 1059-1069. Impact F., dependence L., Cratering Geophysical R. chemical Pergamon, J. G. Clay and A. 1042. diagenetic Fetzer Cratering and Couch 0. R. (1980) Planetary Rev. No. and Sci. K., (1979) F. K. XI, Ernstson Pepin, mechanics Institute Technology. A. T. calcites. Explosion 48 AFWL-TR-77-242. 18, G. A. Conf. and p. (D. cratering J. composition F. R. Shock-induced (1974) pp. Geology of P. N.Y. 885-887. (1981) D., 196-202. F., history (1977) and Investigations J. mechanisms Polkanov Science Kuiper, crater 7th, K. Goter Roddy, Fetzer Amer. • Predicting at R. (1977) Provided An Cratering McGraw-Hill, analogs p. Shock Meteor of B. of Lunar morphology 3027-3056. E. of experimental eds.), Eniwetok XII, J. J. Merrill, the R. Y. The Sci. R., A., effects the attenuation 0. observed 330 for mineral Crater, Decaturville and of A. p. by p. Goter Tremba Ries calcareous 274, (D. Pepin, the bowl-shaped, pp. 301-336. eds), 934--936. (1975) the Planetary in Atoll N.Y. on impact 61-83. J. Eniwetok Arizona. solubility E. calcite NASA investigation p. Mars and E. in Roddy, R., (abstract). at The 296 343--404. Chicago, impact corals. L., laboratory-scale Lunar crater. terrestrial R. Walter Institute, from pp. Astrophysics both Boltysh In Walter B. from central Nuclear R. The Merrill, structure, yes Amer. Pergamon, In Cactus and Abstracts D.R., IL. of 0. water Impact Moon, Houston. D. impact and depression-a uplift, transient Planetary Pepin, Craters. J. R., and eds.), Crater. data; no Data Sci. Missouri. Meteorites and high-explosive and with and N.Y. structures. Wendland (abstract). and 1, p. application System crater Air Wendland Explosion Geochim. Program, multiring Institute, 2nd 687-702. R. Force fossil U.S. ser., size and V. In B. In