Cretaceous-Tertiary Boundary Sequence in the Cacarajicara Formation, Western Cuba: an Impact-Related, High-Energy, Gravity-ﬂow Deposit

Geological Society of America Special Paper 356 2002

Cretaceous-Tertiary boundary sequence in the Cacarajicara Formation, western Cuba: An impact-related, high-energy, gravity-ﬂow deposit

Shoichi Kiyokawa Department of Geology, National Science Museum of Tokyo, 3-23-1, Hyakunin-cho, Shinjuku-ku, Tokyo 169-0073, Japan Ryuji Tada Department of Earth and Planetary Science, Graduate School of Science, University of Tokyo, 7-3-1 Hongo, Tokyo 113-0033, Japan Manuel Iturralde-Vinent Museo Nacional de Historia Natural, Obispo No. 61, Plaza de Armas, La Habana Vieja 10100, Cuba Takafumi Matsui Eiichi Tajika, Shinji Yamamoto, Tetsuo Oji, Youichiro Nakano, Kazuhisa Goto, and Hideo Takayama Department of Earth and Planetary Science, Graduate School of Science, University of Tokyo, 7-3-1 Hongo, Tokyo 113-0033, Japan Dora Garcia Delgado Consuelo Diaz Otero Instituto de Geologia y Paleontologia Via Blanca y Linea del Ferrocarril San Miguel del Padron, La Habana 11 000, Cuba Reinaldo Rojas Consuegra Museo Nacional de Historia Natural, Obispo No. 61, Plaza de Armas, La Habana 10100, Cuba

ABSTRACT

The Cacarajicara Formation of western Cuba is a more than 700 m thick calcareous clastic sequence that contains shocked quartz throughout, and spherules. Three members are recognized. The lower member consists of limestone and chert boulders, and disconformably overlies Cretaceous deep-water turbidite. It is characterized by: (1) a grain-supported fabric with only a small amount of matrix, (2) 5–15 cm, well- sorted clasts and occasional boulders, (3) reversely graded, discoidal or rectangular boulders showing a preferred orientation, (4) abundant shallow- and deep-water carbonate clasts in a well-mixed fabric, (5) direct contact between adjacent clasts, and (6) hydrostatic deformation within a black clay matrix. This evidence suggests that the lower member was deposited under conditions of high-density and high-speed laminar flow. The middle member consists of upward graded, massive to well-bedded, homogeneous calcarenite. Unusual fluid-escape structures in the thick calcarenite suggest that this member formed by high-density turbidity suspension. The upper member consists of fine calcarenite mudstone; there is no evidence of bioturbation. We infer that it was deposited from a dilute, low-density suspension.

Kiyokawa, S., Tada, R., Iturralde-Vinent, M., Masui, T., Tajika, E., Gracia Delgado, D., Oji, T., Nakano, Y., Goto, H., Takayama, H., and Rojas-Consuegra, R., 2002, More than 700-m-thick Cretaceous-Tertiary boundary sequence of the Cacarajicara Formation, western Cuba; Ejecta induced high-energy ﬂow deposit, in Koeberl, C., and MacLeod, K.G., eds., Catastrophic Events and Mass Extinctions: Impacts and Beyond: Boulder, Colorado, Geological Society of America Special Paper 356, p. 125–144. 125 126 S. Kiyokawa et al.

On the basis of these criteria, the Cacarajicara Formation is interpreted to be a single hyperconcentrated flow that was formed by high-energy and high-speed concentrated flow. The south-southeast paleocurrent direction suggests that this high- energy flow originated on the Yucatan platform and was triggered by the Chicxulub impact. We propose that a gigantic flow deposit was induced by earthquake-generated collapse of the Yucatan platform margin owing to ballistic flow from the Chicxulub impact.

INTRODUCTION on the lower member, which contains a thick clastic sequence. We also discuss the possible depositional mechanisms respon- Impact-related sedimentary deposits have been described sible for this thick sequence. at Cretaceous-Tertiary (K-T) boundary sites in the Yucatan Pen- insula region (e.g., Pope et al., 1999). In addition, coarse clastic REGIONAL GEOLOGIC SETTING sequences of impact origin have been reported from marginal areas of the adjoining Gulf of Mexico (e.g., Smit, 1999), and From Cretaceous to Eocene time, the Cuban island arc are inferred tsunami or gravity flow deposits (Bourgeois et al., moved northeastward along the southeast margin of the Yucatan 1988; Bohor, 1996; Smit et al., 1996). In the central Gulf of Peninsula (Fig. 1) (Pindell et al., 1988; Ross and Scotese, Mexico and Caribbean Sea, debris-flow deposits at some Ocean 1988). Fragments of the Yucatan block were detached and Drilling Program sites have been interpreted as originating from moved at least 350 km by left-lateral transform motion in the a collapsed platform margin (Alvarez et al., 1992; Bralower et Paleocene to early Eocene and formed the Guaniguanico terrane al., 1998). Proximal deposits of impact origin have also been (Rosencrantz, 1990; Iturralde-Vinent, 1994b). The Cretaceous discovered east and south of the Yucatan Peninsula. The nearest Cuban island arc finally collided with the North American con- such outcrop is on Albion Island, Belize, ϳ350 km south of tinent and formed a collisional fold and thrust belt (Iturralde- the Chicxulub crater (Ocampo et al., 1996; Pope et al., 1999). Vinent, 1994a, 1994b; Gordon et al., 1997). The orogeny in The East Yucatań oil field, which is located 350–600 km from western Cuba was characterized by collision and strike-slip de- the crater, contains a thick layer of impact ejecta and clasts formation during the Paleocene and early Eocene and resulted (Grajales-Nishimura et al., 2000). Deep core data from the cra- in very complex geology (Gordon et al., 1997). ter have revealed detailed characteristics (Hildebrand et al., Western Cuba consists of the Pinos and Guaniguanico ter- 1991; Sharpton et al., 1996). However, the record from the con- ranes (Iturralde-Vinent, 1994a; Kerr et al., 1999). The Pinos ter- tinental shelf to the oceanic basin on the east and south side of rane is a medium pressure–medium temperature metamorphic the Yucatan Peninsula is still poorly known. sialic complex. The Guaniguanico terrane contains ophiolite- Western Cuba consists of a Paleogene orogenic belt formed bearing thrust-nappe sequences of Paleocene to early Eocene by interaction between the North American and Caribbean age (e.g., Cajalbana ophiolite: Pszczolkowski, 1994), and was plates (Pindell and Barrett, 1990; Ross and Scotese, 1988; Gor- strongly affected by Paleocene–middle Eocene strike-slip de- don et al., 1997). The orogenic belt in western Cuba contains formation during the opening of the Yucatan basin (Rosen- Late Cretaceous to early Tertiary sequences that include a thick, crantz, 1990). The Guaniguanico terrane consists of several tec- well-preserved late Maastrichtian section consisting of the tonic belts, one of which is the Rosario belt (Iturralde-Vinent, Cacarajicara and Penãlver Formations (Pszczolkowski, 1986; 1996). The Rosario stratigraphic sections include continental Bohor and Seitz, 1990; Piotrowska, 1993; Iturralde-Vinent, slope and rise hemipelagic deposits of Late Jurassic to Late 1992, 1994a, 1994b, 1996). The depositional environments and Cretaceous age, as well as Paleocene and Eocene foreland de- trigger events for these unusually thick formations have been posits (Pszczolkowski, 1978, 1994; Iturralde-Vinent, 1994b; discussed, and several origins have been proposed, including Bralower and Iturralde-Vinent, 1997). The Guaniguanico ter- orogenic-volcanic debris deposits, impact-related ejecta, tsu- rane is overlain by ophiolites and volcano-sedimentary rocks of nami deposits, and earthquake-related megaturbidites (e.g., the Bahıá Honda–Matanzas allochthon. Well-preserved K-T Palmer, 1945; Pszczolkowski, 1986; Bohor and Seitz, 1990; boundary sequences in western Cuba include the Moncada For- Iturralde-Vinent, 1992; Takayama et al., 2000). End-Cretaceous mation in the Los Organos belt (Tada et al., this volume), the plate reconstructions (Iturralde-Vinent, 1994a) indicate that the Cacarajicara Formation in the Rosario belt, and the Penãlver study site was situated near the eastern margin of the Yucatan Formation in the Bahıá Honda–Matanzas allochthon (Takay- Peninsula, and may preserve proximal evidence related to the ama et al., 2000). K-T impact. The study area is located near Loma Cornelia, along the In this chapter we describe the lithologic characteristics of road from Soroa to Bahıá Honda, ϳ10 km north of the town the unusually thick Cacarajicara Formation, focusing especially of Soroa. There are excellent outcrops along an adjacent river, Cretaceous-Tertiary boundary sequence in the Cacarajicara Formation, western Cuba 127

84º W 83ºW 82ºW

Bahía Honda-Matanzas belt 50 km Peñalver Formation La Habana Cacarajicara Matanzas 23ºS Formation Guaniguanico Terrane Rosario belt Soroa 4000 m Los Organos impact crater 500 m 22º30'S belt Rosario belt fault Cacarajicara Formation Cuba Jurassic-Cretaceous 500 m deep-water facies Jurassic limestone Chicxulub LEGEND Los Organos belt Late Paleocen–Eocene Cretaceous shallow-water 4000 m shallow-water facies facies 4000 m Early Paleocene Jurassic-Cretaceous 500 m Pinar deep-water facies limestone Yucatán 22º20'S del Rio Jurassic continental Bahía Honda-Matanzas belt shelf facies 500 m Cretaceous deep-water Serpentinite mélange 500 m 4000 m facies Peñalver Formation slip direction of fault Cretaceous deep-water 1000 m 0 1000 km facies strike-slip fault

Figure 1. Geologic map of western Cuba, showing Guaniguanico terrane and location of Cacarajicara Formation outcrops (after Pushcharovsky, 1989). Map on right shows location of western Cuba and Yucatan Peninsula, with respect to buried Chicxulub impact crater and topographic centerlines. Dashed circles represent proposed crater diameters: 180 km (Hildebrand et al., 1991) and 300 km (Sharpton et al., 1992, 1996). where we conducted mapping and sampling (Fig. 2). We sam- ceous Polier Formation is partly disturbed by a reverse fault pled along roadcuts and river bluffs continuously every 5 m that dips 60Њ south and has steeply plunging lineations. This vertically, collecting the clasts and matrix in the breccia se- disconformable (erosional) contact is preserved in the hanging quences. Thin sections were prepared, and grain separation was wall of the fault. The upper boundary was disturbed by strike- accomplished by dissolution in hydrochloric acid and magnetic slip and shear deformation and is overlain by the Paleocene separation. More than 100 thin sections of rock chips, and 100 Ancon Formation. The Cacarajicara Formation is underlain by acid-dissolution samples were used to determine the grain type the Santonian?-Campanian-Maastrichtian Moreno Formation and size, and grain-boundary conditions, by using a petro- or older units at some other localities (Pszczolkowski, 1978, graphic microscope, energy-dispersive spectrometer (EDS; 1994). JEOL 5400), and electron probe microanalyzer (EPMA; JXA- 8800M) (for details see Yokoyama et al., 1993). LITHOSTRATIGRAPHY CACARAJICARA FORMATION The Cacarajicara Formation is an ϳ700-m-thick, upward- The Cacarajicara Formation is present only in the Rosario ﬁning, homogeneous, calciclastic sequence. It can be subdi- belt as nearly continuous strips 0.5–1.0 km wide and to 100 km vided into the Lower Breccia, Middle Calcarenite, and Upper long in an east-west direction (Fig. 1). Latest Maastrichtian rud- Lime Mudstone Members (Fig. 4). The boundaries between the ists, foraminifera, and nannofossils occur in the matrix and in members are gradual; there are no sharp lithologic discontinu- fossil-bearing limestone fragments, but no Paleocene fossils ities except for the contacts with Eocene sediments. have ever been reported (Pszczolkowski, 1986; Iturralde- In order to understand the depositional mechanism for the Vinent, 1992). Cacarajicara Formation, we focused our study on the detailed sedimentary structures and lithologic characteristics, including CROSS SECTION grain composition, size, shape, and boundaries, and matrix components. We used microscopic point counts for the Middle The Cacarajicara Formation dips 70Њ–80Њ to the north, as Calcarenite and the Upper Lime Mudstone Members and out- indicated by the thin pebbly layer in the calcarenite (Fig. 3); crop point counts for the Lower Breccia Member. Grain-size the pressure-solution cleavage preserved in the calcarenite dips variations were determined from 200 counts at one locality in 30Њ to the north. The lower boundary with the Lower Creta- each member. 128 S. Kiyokawa et al.

LEGEND Serpentinite shear zone Cacarajicara Formation sandstone and/or Upper Lime Mudstone siltstone (Eocene) Member B micritic limestone San Nago River lime mudstone (Ancon Formation) Middle Calcarenite Member Polier Formation sand-sized calcarenite bedding pebbly calcarenite (strike, dip direction) Lower Breccia Member pressure solution 99-44 cleavage Ancon 99-43 pebble breccia Formation n 70 e, 8 n fault reverse fault 99-42 cobble-pebble breccia disconformity n 75 e, 65 n 99-41 cobble breccia grain measurement area 99-40 (reverse graded 99-38 99-39 sample point 99-37 boulder clasts) Upper Lime 99-36 98-26 99-35 Mudstone Member 99-34 98-25 99-33 Middle 98-24 Calcarenite member 99-0 50 m 500 m 99-30 upper 99-2999-28 99-31 99-2799-26 submember 99-2599-24 n 74e, 62 s San Nago 98-23 99-2399-22 99-2199-20 98-22 99-1999-18 river 98-21 n 75 e, 38 n n 75 e, 21 n Eocene 98-20 n 39 e, 38 n Mx-6 98-19 n 58 e, 80 n upper sediments n 43 e, 48 n 99-7 submember 98-18 99-6 n 75 e, 87 n 98-17 99-5 98-16 99-17 99-4 98-15 99-1699-15 99-3 99-1499-13 Mx-5b 98-14 99-1299-11 99-2 99-1099-9 98-13 99-8 99-1 98-12 98-11 lower Lower Breccia Member 99-0 98-10 submember 98-9 Mx-5a Middle middle Mx-6 submember Calcarenite Mx-4 Member Mx-5b 0 98-8 Mx-5a 98-7 98-6 Mx-4 98-5 Mx-3 Mx-3 Lower 98-4 Mx-2 Breccia 98-3 Mx-1 lower Member 98-2 98-1 n 62 e, 78 n submember Mx-2 n 66 e, 76 n n 76 e, 78 n Mx-1 n 70 e, 45 s n 62 e, 78 n n 59 e, 80 n A Polier Formation n 66 e, 76 n Polier Formation

Figure 2. Geologic map of Cacarajicara Formation along San Nago River (left). Geologic map of Lower Breccia Member (right). Black dots and numbers are sampling points and sample number.

Lower Breccia Member spherules. The middle submember contains the pebble- to cobble-size breccia; there are no larger boulder clasts (Fig. 5C). The upper submember contains pebble-size breccia; black chert The Lower Breccia Member is more than 250 m thick and pebbles are more homogeneous in size than in the middle and is composed of cobble- to pebble-size clasts consisting of shal- lower submembers. low- and deep-water limestones, black chert, bedded chert, and Grain composition. More than 50% of the clasts in the greenish shale (Fig. 5, A, B, and C). The breccia is well sorted Lower Breccia Member are calcareous angular or rounded lime- and grain supported, with only a small amount of matrix. Dis- stone. The angular limestone is composed of rudist limestone, coidal or rectangular boulders ﬂoating among the cobble-pebble massive coarse calcarenite, foraminiferal limestone, and micri- clasts are conspicuous (Fig. 5, B and C). tic limestone with black chert layers. Small amounts of oolitic The Lower Breccia Member is subdivided into the lower, limestone and calcareous algal mat limestone are also present. middle, and upper submembers (Fig. 6). The lower submember The rounded limestone has a more eroded surface than the an- contains the cobble- to boulder-size breccia and larger boulder gular limestone, and is composed of micritic limestone, fora- clasts (Fig. 5B). The black clay matrix contains some shocked miniferal limestone, and dolostone, 3–10 cm in diameter quartz; the matrix in the basal part of this submember contains (Fig. 7). B serpentinite shear zone Ancon Formation 100 m Upper Lime Mudstone Member 0 black chert clast fluid-escape structure pressure-solution cleavage fault reverse fault strike-slip upper submember pipe-and-dish shaped fluid-escape structures pebble breccia pebble-cobble breccia pebble-cobble breccia (with boulder clasts) serpentinite shear zone Lower Brecia Member Brecia Lower Polier Formation Polier Middle Calcarenite Member Middle Calcarenite lower submember lower Cacarajicara Formation upper submember middle submember lime mudstone sandsize calcarenite pebbly calcarenite Lower Breccia Member Breccia Lower Upper Lime Mudstone Member Member Middle Calcarenite Ancon Formation Cacarajicara Formation lower submember A Figure 3. Cross section of Cacarajicara Formation. LEGEND Polier Polier Formation 129 130 S. Kiyokawa et al.

#/# = grain number of shocked quartz rare Sample number with PDFs / total number of quartz common 800 Ancon Formation grains massive foraminiferal 98- 99- #/# (%) limestone 44 43 41 Upper 26 25 39 Lime Mudstone 38 39/497 7.8 37 Member 36 24 34 9/99 9.0 fine sandstone 33 Dilute low-density suspension deposit - siltstone 600 30 23 28 24 22 medium- to fine 22 21 20 - grained 20 18 calcarenite 16 19 12 48/253 19.0 Middle 18 10 17 6 upper submember Calcarenite 16 5 24/184 13.0 9/110 8.1 Member 15 4 pipe- and dish-shaped 14 3 fluid-escape structures 13 400 2 20/191 10.5 12 11 1 44/452 10.0 (homogeneous) High concentration turbiditic suspension deposit coarse-grained 10 calcarenite 9 lower submember 0

8 Mx-6 49/588 8.3 pebble breccia

upper submember 7 200 pebble-cobble breccia Mx-5b Lower 6 23/192 12.0 5 Breccia Mx-5a middle submember 18/253 7.1

Member 4 Mx-4 63/712 8.8 cobble breccia 3 High-concentrated laminar-flow deposit (grain supported) with discoidal boulder clasts Mx- 3 48/272 17.6 (reverse grading) 2 1 15/101 17.6 lower submember Mx-2 10/96 14.9 Mx-1 26/135 19.3 0 m 59/293 17.7 Polier Formation (%) Cretaceous sandstone/shale alternation (turbidite)

spherules proportion location shocked quartz of shocked of nannofossil with planer quartz deformation features Figure 4. Lithologic column for Cacarajicara Formation. Squares and line of sample numbers indicate points in thin sections where proportion of shocked versus unshocked quartz was counted. Occurrences of spherules, shocked quartz, and nannofossils are shown in right columns. PDF is planar deformation feature. Cretaceous-Tertiary boundary sequence in the Cacarajicara Formation, western Cuba 131

Figure 5. A: Overview of Lower Breccia Member. Continuous outcrop is preserved along Nago River. B: Basal part of Lower Breccia Member. Breccia contains discoidal and/or rectangular clasts of black chert, greenish shale, and gray limestone. Pebble size fraction mainly contains rounded limestone clasts. Matrix in these clasts is very poorly preserved. C: Lower submember of Lower Breccia Member. Note black chert and greenish shale particles preserved in pebbly limestone clast. D: Pebbly calcarenite of lower Middle Calcarenite Member. White margin of black chert clast is replaced by carbonate. E: Elongated fluid-escape pipe structures in homogeneous calcarenite in upper Middle Calcarenite Member. Weak subhorizontal foliation is pressure-solution cleavage. F: Fluid-escape vein structures in homogeneous calcarenite of upper Middle Calcarenite Member. Diffuse webby laminations (slanting to right) of fluid-escape structures are well preserved in this sequence, and resemble structures seen in Penãlver Formation. Lens cap, 55 cm for scale. G: Rectangular bedded red chert clast in uppermost lower submember of Lower Breccia Member. Hammer, 35 cm for scale. H: Black chert clast in upper part of lower submember of Lower Breccia Member. Scale is film cap in center. I: Black siliceous sandstone clast in upper part of lower submember of Lower Breccia Member. Sandstone is 1 m thick and more than 10 m long. Note that there is no fault in this calcarenite.

Chert represents 40% of the pebble- to cobble-size clasts, basic rocks (Fig. 8B), quartz-rich sandstones (Fig. 5I) and which consist mainly of black chert (Fig. 5, B, C, and H), black pelitic and psammitic schists. The minor grain compositions chert associated with foraminiferal limestone, and red radio- imply a variable source area within a volcanic and orogenic larian chert (Fig. 5G). The black chert clasts are similar in li- region. thology to the black chert in the Cretaceous deep-water Pons Grain size and shape. There are two modes of grain sizes Formation of the Guaniguanico terrane. in the lower submember of the Lower Breccia Member (Fig 6). Minor clast components include green shale (Fig. 5G), The smaller clasts are ϳ3–15 cm and no size grading is obvious green altered volcanic rock, trachytic basalt (Fig. 8A), vesicular (Fig. 5C); this range composes 60%–70% of this member by 132 S. Kiyokawa et al.

Figure 5. Continued volume. The larger clasts are 30–300 cm (average long axis 40 abraded into softer, rounded limestone clasts (Figs. 5, B and C, cm; Fig. 5G), and compose to 5% by volume; this clast size and 8D). There are many hydrofractured limestone clasts in the range exhibits reverse grading (Fig. 6). The uppermost part of matrix alongside the larger clasts. Cracked chert clasts, matrix the lower submember contains the largest clasts, including some clay intrusion structures, and highly brecciated material form a that are Ͼ2-m-long, discoidal to rectangular black chert, and jigsaw puzzle-like mosaic or texture preserved along the lime- others that are Ͼ10-m-long, 80-cm-thick, black, less calcareous stone clast margins (Figs. 8F and 9, A and B). Some black chert sandstone blocks (Fig. 5, G, H, and I). The upper and middle is fractured, and sharp cracks are filled by the general matrix submembers lack large boulder clasts in the gradually formed clay (Fig. 8, E and F). Along narrow cracks in the large dis- fining-upward sequences. coidal boulders, dark brown clay matrix contains brecciated The largest angular clasts in the Lower Breccia Member pebbly micritic limestone (Fig. 9A). were not affected by abrasion. The cobble- to pebble-size car- Matrix. The matrix composes Ͻ1–3 vol% of the Lower bonate clasts are subrounded and subangular, and have homo- Breccia Member, and fills the very narrow spaces between the geneous compositions. The minor clast components, such as closely packed clasts. This matrix is composed of dark brown green shale, schist, and volcanic rocks, are mostly Ͻ5cmin to black clay and some sand-size carbonate fragments. Accord- diameter and well rounded. They were probably reworked long ing to EPMA element mapping, there are many dolomite frag- before deposition in the Cacarajicara Formation. ments in this clay matrix. The matrix is composed mainly of Grain-boundary condition. The clasts are mostly in direct brown to dark brown clay, and small amounts of sand-size car- contact with each other; harder angular grains are partly bonate, siliceous, and opaque grains (Fig. 9C). The basal part Cretaceous-Tertiary boundary sequence in the Cacarajicara Formation, western Cuba 133

Figure 5. Continued in this member exhibits an especially low content of limestone very homogeneous fabric (Fig. 5, E and F). The sand grains are grains. Sand-size carbonate grains in the clay matrix increase mainly composed of micritic limestone fragments and forami- upsection throughout the Lower Breccia Member. niferal skeletons, and a smaller amount of larger bioclasts. The massive, coarse calcarenite contains many unusual fluid-escape Middle Calcarenite Member structures similar to those reported in the Penãlver Formation near Havana (Bronnimann and Rigassi, 1963; Takayama et al., 2000). Fluid-escape structures in this submember are mainly ϳ The 300-m-thick Middle Calcarenite Member is com- pillar, pipe, and spiral shaped; there are some dish-shaped struc- posed of well-sorted, massive, homogeneous calcarenite, which tures (Fig. 5, E and F). exhibits upward fining and distribution grading. A partly pre- Grain composition. The calcarenite of the Middle Calcar- served pebbly bed and parallel laminations are rarely present enite Member consists of more than 85%–90% calcareous as bedding in this homogeneous calcarenite. The boundary be- grains, including two types of fragments: shallow-water bio- tween the Lower Breccia and the Middle Calcarenite Members clastic limestone, comprising rudists, stromatolites, and oolite, is a fault contact within the Eocene turbidite sequence. How- and deep-water fragments of micritic limestone and foraminif- ever, the rock gradually changed to fining upward. Except for the chert grains, the grain composition resembles the upper sub- eral limestone (Fig. 7). The lower submember mostly contains member of the Lower Breccia and the lowest Middle Calcar- rudist, bioclastic, and foraminifer limestone fragments, and the enite Members. upper submember mainly contains foraminiferal grains and mi- The Middle Calcarenite Member can be subdivided into critic limestone (Fig. 7). The remaining 15%–10% of the grains upper and lower submembers. The lower submember is com- are quartz and feldspar (6%–10%), chlorite-smectite-replaced posed of coarse granular carbonate calcarenite with pebble-size volcanics or serpentinite (3%–4%), and other minerals (Fig. 7). clasts (Fig. 5D). The calcareous sand grains are mainly com- Single-crystal piemontite, indicative of low- to medium-grade posed of limestone fragments of rudists, algal mats, and fora- metamorphism, and zircon and chrome spinel are present in the minifers. The pebble-size clasts are fragments of black chert, matrix in small amounts. greenish shale, volcanic rocks, and schist. The percentage of Calcareous grains compose Ͼ80 vol% of both the Caca- pebbly clasts gradually decreases upward. rajicara and Penãlver Formations, but the relative presence of The upper submember is composed of massive, coarse- to associate minerals differs significantly. On the basis of the mag- medium-grained, calcareous calcarenite, with a well-sorted and netically separated samples from each formation, the Cacara- 0 m 200 400 600 oeta lssaeo w ye:mjr37c iegopadmnrbudrsz ru.Szso ole lssices rmlwrt pe nlwrsubm lower in upper to lower o from diagram increase variation clasts grain-size boulder Detailed of Sizes Right: group. axis. size long boulder grain on minor of fluctuations and average group and shows size axis point cm short circle 3–7 on with of major Width size part types: Member. Darkest grain two co Breccia respectively. average grains of Member. Lower sizes, 200 are for show grain on used clasts Member based smallest method that Breccia is and field-observation Note point Lower largest and data of show Each Member points sequence. lines Calcarenite this rhombus Middle thick in and above points Square used data method variation. 33 Thin-section are size There data. Formation. size Cacarajicara maximum of and distribution Grain-size Left: 6. Figure

Lower Breccia Middle Calcarenite Upper Lime Member Member Mudstone Member

locality of samples 99-0 99-1 99-2 99-3 99-4 99-7 99-11 99-13 99-17 99-19 99-21 99-23 99-25 99-29 99-31 99-44 99-33 99-34 99-36 99-37 99-38 99-39 99-41

sample

number 0.001

aiu ie(gray dotsareshortaxis) maximum size average size minimum size

0.01 0.1

thin line:average grain of shortaxis Grain size(mm) thick line:average grain oflongaxis

100

1000

10 4 100 200 300

0 m Lower Breccia member

grain counted lower middle upper Middle locality submember submember submember Calcarenite Member (lower subm.) 20 40 20 40 20 40 20 40 20 40 60 20 40 60 80 20 40 20 40 0 0 0 0 0 0 0 0 number of grains 02 040 30 20 10 0 40 30 20 10 0 SHORT AXIS (cm) 20 40 20 40 20 40 20 40 20 40 20 40 20 40 60 80 20 40 0 0 0 0 0 0 0 0 number of grains 010 2030405060 LONG AXIS ne oso iiu,average, minimum, show to unted sz aito.Nt htti and thin that Note variation. -size (cm) oe rci Member. Breccia Lower f me fLwrBreccia Lower of ember 60 60 60 hdwsosgrain- shows shadow 0100 80 010220 100 80 010120 100 80 120 (cm) 500 A: Grain variation in thin section C: Grain variations from grain HCl dissolution residue HCl disolution residue Carbonate grain other count quartz 98-23 Magnetic 133 LEGEND HCl dissolution separated grains plagioclase (albite) grains 98-21 micrite 98-25 K-feldspar 183 chlorite + smectite massive N = number of grains 98-20 242 limestone chlorite + smectite + albite foraminifera chrome-spinel 98-19 grain (sample number) 432 rudists 98-22 pyrite biotite (altered) 98-18 244 bioclast foraminifera goethite 98-17 271 clast N = 92 muscovite 98-16 serpentine 98-24 408 and/or chlorite Magnetically separated sample 98-15 404 volcanics chlorite + smectite chlorite + smectite + albite 98-14 quartz N = 220 488 plagioclase chrome-spinel 98-13 209 K-feldspar 98-17 pyrite chert biotite (altered) 98-12 204 rutile shale N = 188 98-11 schist goethite 53 98-16 barite sandstone 98-10 185 spinel Peñalver Formation 98-9 29 N = 257 Middle Member Serpentine B: Grain variation from outcrop 98-14 Clay 99-0 Chlorite 221 LEGEND Hornblende angular N = 98 Epidote limestone clast 72 Celestite chlorite + smectite Mx-6 rounded 98-11 limestone clast Grossular 247 chert and/or Spinel Mx-5b limestone (Titanite) N = 276 N = 283 199 black chert Serpentine Mx-5a clay matrix Clay 98-12 Lower Member Chlorite 275 shale Hornblende Mx-4 Staurolite sandstone N = 146 Epidote

277 Grossular chlorite + smectite Mx-3 schist Clinopyroxene 98-9 Clinopyroxene Mx-2 volcanics (hedenbergite) 155 Biotite mudstone Pyrite Mx-1 N = 220 Ilmenite 122 conglomerate Magnetite Carbonate grains other Spinel (Titanite) N = 172 Rutile 0 50 100% Goethite Magnetically Sphene (Vol. %) N = 145 separated sample Chalcopyrite

Figure 7. Thin-section and outcrop-scale grain-type variation of nondissolved samples from throughout Cacarajicara Formation (left). Grain composition of HCl dissolution and magnetically separated residue (right). Box on right shows data comparable with Pen˜alver Formation, which has more variable grains. Considering metamorphic alteration, composition of grains between Cacarajicara and Pen˜alver Formations is very similar. 136 S. Kiyokawa et al.

Figure 8. A: Thin-section microphotograph (crossed polarizers) of basaltic clast from lower submember of Lower Breccia Member. B: Thin section of vesicular shard in Middle Calcarenite Member: B, crossed nicols; B’, parallel polarizers. Note that grains are ﬁlled by chlorite, although some portions of shard are isotropic and may be mostly glass. C: Thin section of well-rounded volcanic grains in coarse calcarenite from Middle Calcarenite Member (plain light). D: Polished section of pebbly clast from Lower Breccia Member. Varied clast types preserved in poor matrix. Rectangle shows E. E: Muddy matrix ﬁlls fracture in green chert. F: Polished section of coarse calcarenite of lower Middle Calcarenite Member. Cretaceous-Tertiary boundary sequence in the Cacarajicara Formation, western Cuba 137

Figure 9. A: Pebbly limestone with black matrix along 3-m-long, disk-shaped clast. Note that limestone float in black matrix has been affected by hydrofracturing. Lens cap, 5.5 cm for scale. B: Thin-section view of margin of limestone grain. Intrusion of matrix preserved in limestone grain in upper submember of Lower Breccia Member (parallel polarizers). C: Thin-section view of matrix from basal part of Lower Breccia Member. Isolated round quartz spherules are preserved. (Square shows more detailed Fig. 13B) E: Microcarbonate pisolith in thin section of medium calcarenite. Pisolith forms radial pattern crystal of carbonate with very thin, spherical shell. jicara Formation preserved only smectite and chlorite grains, stone. This size fractionation may have resulted from deposi- but the Penãlver Formation, especially the middle member, con- tional sorting of the original grains. tains serpentine, clay, epidote, chlorite, hornblende, and gros- Matrix. Matrix is rarely present in the well-sorted calcar- sular (Fig. 7). This difference probably reflects the low-grade enite, and when present it consists of very fine calcareous clay metamorphism of the Rosario belt. In addition, minerals such in the narrow spaces between sand-size grains. Calcite pisoliths, as serpentinite, clay, and hornblende may have decomposed or 200–300 lm and having very thin skin, are well preserved in altered to chlorite-smectite minerals (Fig. 7). the matrix of medium-fine calcarenite. They appears as 10 or cm thin sections, and compose 4 ן Grain size and shape. The calcarenite in this member is more grains seen in 3 well sorted, and the carbonate grains are mainly angular, Ͻ10% of the matrix. whereas the volcanic, schist, and shale grains are well rounded. The rounded noncarbonate grains may have a reworked origin. Upper Lime Mudstone Member The lower submember contains large fragments of rudist, bioclastic, and foraminiferal limestone. The upper submember The Upper Lime Mudstone Member is more than 100 m contains small grains of foraminifer skeletons and micritic lime- thick, and consists of homogeneous, massive, calcareous, fine 138 S. Kiyokawa et al. calcarenite and lime mudstone. The lithology gradually changes Analytical methods from that of the underlying Middle Calcarenite Member. The upper boundary with the Paleocene Ancon Formation is a fault Isolation of grains. We fragmented ϳ100 samples of calcar- contact, and the exact boundary is not observable. This member enite, weighing ϳ50 g each, to a grain size of 1 cm to few consists of calcareous, fine calcarenite and lime mudstone with millimeters. The samples were then treated with dilute hydro- some foraminifer skeletons, shallow-origin bioclasts, and black chloric acid for ϳ30 min and after complete dissolution of the carbon fragments that might be wood. Foraminifer skeletons carbonate material, the residue was magnetically separated into are very rare in the uppermost part of this member. Poorly magnetic, weak magnetic, and nonmagnetic grains. Thin sec- preserved sedimentary structures are present, such as cross- tions of the three kinds of residues (ϳ1–3 g) were prepared, lamination, bioturbation, or fluid-escape structures, in addition and these thin sections were used for counting and measuring to faint parallel bedding. The overlying Ancon Formation con- grains under optical and electron microscopes. The composition tains many foraminifers and exhibits a bioturbation texture. of the grains was determined by EDS or EPMA. There are some nannofossils in the limestone (Fig. 4), in- The nonmagnetic residue of shocked quartz was treated cluding Micula dexussata, which ranges from Coniacian to with silica-saturated hydrofluorosilicic acid for three days, so Maastrichtian; no Paleocene fossil was found in this member. that other minerals were completely dissolved. After making a thin section of the new residue, we produced a grain map of PALEOCURRENTS the thin section in a slide scanner. These scanner images make it easy to identify the normal and deformed quartz. Shocked Imbricated clast structures indicative of paleocurrents are quartz was identified by the presence of more than two sets of present in the Lower Breccia Member; the discoidal and/or rec- planar deformation features (PDFs: Fig. 11, A, B, and C), which tangular clasts show flow orientation. We measured the dips have distinct angles from the c-axis in the quartz (e.g., Sto¨ffler and strikes of clasts Ͼ40 cm in greatest diameter. The estimated and Langenhorst, 1994; French, 1998). When looking for de- current orientation is corrected for folding; the fold plane dips formed quartz on a map, we try to measure the PDFs, which 80Њ north with zero plunge of the axis (Fig. 10). The area of are characterized by at least two sets of straight planar features. Cacarajicara Formation distribution is 100 km long and the li- We exclude the spaced and planar fracture (PF) structures thology is very uniform, and we estimate that the folding plunge formed at this stage. Measuring the orientation of the PDFs of in this area is very shallow and not involved in crustal rotation. quartz in the thin section was performed on a universal stage The disk-shaped clasts preserve imbricated structures, and the (e.g., Montanari and Koeberl, 2000), and then plotted in fre- paleocurrent evidently flowed from north-northwest to south- quency distribution histograms. southeast in current terms (Fig. 10). We processed the magnetically separated residue to obtain spherules. Spherules were searched for under a stereomicro- IMPACT EVIDENCE scope, then the spherule surfaces were observed by electron microscopy. At this stage, we picked up only smooth spherules. Shocked quartz and spherules of probable impact origin After we examined the spherule surfaces, each grain was glued (e.g., Bohor and Glass, 1995; French, 1998) are present in the to a slide glass and we made half-cut polished sections for ob- Cacarajicara Formation. Carbonate pisoliths are also preserved servation by EDS and EPMA. Microfossils such as radiolaria, in the calcarenite, which might be a microcarbonate pisolith ostracoda, and foraminifera were distinguished at this stage. (Pope et al., 1999). The radiolaria, which are totally replaced with goethite, have round tests with well-regulated small openings and are very flow common in this formation. The ostracoda and foraminifera were clasts imbrication preserved only as lattice shapes replaced by oblong clay min- pre-rotation breccia plane erals. N N Reoriented N Shocked quartz

Shocked quartz is found throughout the Cacarajicara For- mation (Fig. 4). PDF orientation has been used as a shock ba- rometer to measure the intensity and distribution of shock pres-

total rotation axis: 0, N 65 E Circle = 7 % sures (Grieve and Robertson, 1976; Dressler and Sharpton, number = 212 80º clockwise rotation NNW to SSE 1997) Most of the PDFs in the shocked quartz from this for- Њ Њ Њ Figure 10. Paleocurrent direction for Lower Breccia Member. Plot mation are concentrated at the x (23 ), p (32 ), f (48 ), and c shows dip and strike of disk-shaped clast, which preserved similar (52Њ) positions from the c-axis of quartz crystals (Fig. 12). The direction. Note data reoriented 70Њ clockwise by N65E horizontal axis. presence of the p plane with a number of different orientation Cretaceous-Tertiary boundary sequence in the Cacarajicara Formation, western Cuba 139

ωπ ξ γ 25

Sample No. set grain 98-24 n=11 n=8 20 98-23 n=12 n=12 98-22 n=21 n=15 98-21 n=23 n=15 98-20 n=26 n=17 98-19 n=38 n=19 15 98-18 n=22 n=3 99-5 n=14 n=3 Mx-1 n=16 n=7 total 173 sets, 99 grains 10 Number of sets 5

0 0 20 40 60 80 Angle of c-axis PDF (degrees) Figure 12. Shocked-quartz planar deformation feature (PDF) orientation diagram.

planes suggests that the shocked quartz in the Cacarajicara For- mation was affected by more than 16 GPa of pressure. The abundance of shocked quartz with PDFs in the Caca- rajicara Formation varies from Ͻ20% to 7% of total quartz grains in the acid-dissolved residue (Fig. 4). The matrix in the basal part of the Lower Breccia Member and the ﬁne sand-size calcarenite in the upper Middle Calcarenite Member preserve shocked quartz in abundances as high as 15%–20% of the total number of quartz grains.

Spherules

The identity of impact-related spherules in the Cacarajicara Formation is still not known with certainty. However, the matrix in the basal part of the Lower Breccia Member contains three types of spherules. The ﬁrst type of spherule is gray, 200–300 lm in diameter, and has a very smooth surface and partly elongated shape (Fig. 13A). Based on backscattered electron images and EDS analysis, this type of spherule is composed of homogeneous clay minerals, mainly smectite. It may be an altered glass spherule. The second type of spherule consists of isolated silica spheroids preserved in the clay matrix within the basal Figure 11. A: Planar deformation features (PDFs) in shocked quartz Lower Breccia Member (Fig. 8B). These spherules are well (crossed nicols) from Middle Calcarenite Member (sample 98-18). rounded and are formed of a quartz crystal with radical extinc- PDF shows x and p planes. B: Backscattered electron (BSE) image tion (Fig. 13B). The third spherule type consists of goethite, of shocked quartz in Middle Calcarenite Member (sample 99-4). PDF which is distinguished by some larger (500–1000 lm in di- shows x and f planes, as measured on universal stage by microscope. C: PDFs in shocked quartz (crossed nicols) in Lower Breccia Member ameter) and other smaller (200–300 lm in diameter) spherules (sample Mx-1). PDF shows p, f, and x planes. (Fig. 8C). The larger spherules are similar in size to those in the Beloc samples (Izett, 1991; Bohor and Glass, 1995). The surface of the goethite spherules is a smooth and irregular plane. 140 S. Kiyokawa et al.

0.1 mm

0.2 mm B

0.1 mm 0.1 mm

C D E Figure 13. A: Gray spherules in matrix of Lower Breccia Member (0.3 mm in diameter, sample Mx-1). Note smectite in each grain. B: Silica- rich spherules in matrix of Lower Breccia Member (0.3 mm diameter). C: Large goethite spherules (sample Mx-1). D: Scanning electron microscope (SEM) image of gray spherule surface (sample Mx-1). E: SEM image of section of goethite spherules (sample Mx-1). Note dendritic texture preserved and overprinted by goethite.

The insides of large goethite spherules are very homogeneous pisoliths in the Middle Calcarenite member might have been and partly preserve a dendritic texture (Fig. 13E) that resembles formed as accretional carbonate tuff from impact-induced cal- the texture seen in the second type of spherule that has been cite vapor. entirely replaced by goethite (Bohor and Glass, 1995). DISCUSSION Carbonate pisoliths Here we review the origin, transportation, and depositional The carbonate pisoliths are well preserved in matrix of the mechanisms of the Cacarajicara Formation. The upward-fining middle-fine calcarenite of the Middle Calcarenite Member (Fig. sequence in this formation was likely formed by one gravity 9D). The matrix is formed of simple 200–300-lm-diameter cal- flow event. The sedimentary characteristics, however, are very cite crystals within a fibrous radial structure. These pisoliths different from those seen in normal turbidite and debris-flow have 1-lm-thick calcite wall that forms perfect spheres. This is deposits. We have focused on the flow characteristics of each a simpler crystal than the laminated ooids or microfossils, and member of this thick formation in order to infer flow transpor- it is not preserved in the other carbonate clasts or carbonate tation mechanisms, and relate these to the Chicxulub impact. grains. Similar pisoliths are also contained in the matrix within the middle member of the Penãlver Formation, which was not Transportation mechanisms metamorphosed. Calcite pisoliths in the spherule layer on Al- bion Island are 7–10 mm in diameter, larger than in the Caca- Lower Breccia Member. The clasts in the Lower Breccia Mem- rajicara Formation. However, a radial structure with 1–2-mm- ber have shallow-water, deep-water, and orogenic belt origins. thick shells is also present (Pope et al., 1999). The carbonate Many limestone and chert breccias resemble those in underly- Cretaceous-Tertiary boundary sequence in the Cacarajicara Formation, western Cuba 141 ing Cretaceous formations. The thick mixed-clast member may suggest that the Upper Lime Mudstone Member was formed by represent a collapse of the continental margin of the Yucatan a continuous, more dilute suspension. platform. We proposed that these thick clasts are transported by Takayama et al. (2000), however, proposed “homogenite,” laminar flow for the following reasons. which is formed by a tsunami, for the middle member of the The cobble- to pebble-size clasts in the Lower Breccia Penãlver Formation. The Middle Calcarenite Member preserves Member are mostly in direct contact with each other and are sedimentary features that are similar to those in the Penãlver similar to those in other grain-flow deposits (Bagnold, 1954). Formation. A tsunami produces mixing and turbidity in ocean Such clasts were affected by the high dispersive pressure of sediments and may occur with or slightly after gravity sliding grain collisions. The grain-boundary conditions around the clay and ejecta flow. The very thick high-density turbidity suspen- matrix, however, preserved hydrofractured clasts, cracked chert sion might have been produced tsunami-induced remixing. clasts, and matrix intrusion structures within limestone clasts. However, it is unknown whether the Cacarajicara Formation The pebble-size carbonate present in the matrix alongside large was influenced by a tsunami wave. boulders, which can be regarded as flow shadows, is preserved Relationship to the Chicxulub impact. The presence of as a highly fractured fabric. There is no evidence that the other shocked quartz and microspherules indicates that the Cacara- cobble- to boulder-size clasts were similarly influenced by this jicara Formation resulted from an impact. The paleocurrent dis- flow shadow. These features imply a high pore-pressure contribution inferred from the boulder imbrication in the Lower dition in this matrix, and the large clasts were fractured by the Breccia Member shows a north-northwest to south-southeast hydrostatic conditions. direction in modern terms. The Rosario belt belongs to an oro- The flow behavior of grain-supported sediments is changed genic terrane, and the basic structure is top-to-the-north verg- by flow speed (Pierson and Costa, 1987). Grain-supporting ence with east-west-striking folds and thrusts (Gordon et al., Њ mechanisms, such as the turbulence, dispersive stress, and flu- 1997). It is difficult to rotate bedding 180 inside such an oro- idization, increase with flow velocity. In this way, with increas- genic belt, so we propose that this paleocurrent flow came from ing pore pressure of the flow matrix, the grains floated and were the depositional area. When the Guaniguanico terrane of west- transported long distances (e.g., Shanmugam, 1996). The ern Cuba is restored to its original orientation at the K-T inter- Lower Breccia Member contains the following characteristics: val, the Cacarajicara Formation was situated on the southeastern margin of the Yucatan Peninsula (Pindell et al., 1988; Ross (1) the reverse-graded and imbricated fabrics of the boulder and Scotese, 1988). In this position, the south-southeast direc- clasts show the shear distribution of flow; (2) direct contact tion of paleocurrents is consistent with the former location of between each clast implies a high dispersive pressure condition; the Yucatan continental margin. and (3) many matrix intrusions and a mosaic or jigsaw puzzle texture alongside limestone clasts also indicate high pore pres- Sedimentation model sures. These features suggest that the Lower Breccia Member formed under laminar flow conditions in a very high speed di- Clastic rocks of the Cacarajicara Formation mainly origi- latant situation (Lowe, 1976; Todd, 1989; Shanmugam, 1996). nated from the collapse of the Yucatan platform (Fig. 14). The Middle Calcarenite Member. The homogeneous and well- deep-water limestone and black chert, which are main compo- sorted calcarenite with deep- and shallow-origin rocks implies nents of this formation, represent continental slope deposition, that the Middle Calcarenite Member formed under extremely whereas shallow-water limestone such as rudist and oolite lime- mixed, strongly turbulent conditions. Sustained steady or quasi- stones and dolomite represent platform margin deposition. The steady current and upward migration of a depositional flow volcanic and metamorphic rocks are also present in the San were required to form such a thick, massive calcarenite with a Cayetano Formation and the Roble member of the Polier For- homogeneous fabric and large-scale grading. This process is mation, which were also located on the continental margin or referred to as high-density turbidity suspension (Kneller and slope along the Yucatan platform. Branney, 1995). The diffused flow laminations in the massive The inferred sedimentation of the Cacarajicara Formation, and well-sorted facies also suggest that the grains belonged to which records laminar flow, high-turbidite suspension, and di- a strong suspension (deposit) environment, rather than a flow luted suspension, resembles the hyperconcentrated flow that has (shear) environment. The many fluid-escape structures also sug- been associated with high-energy and high-speed flows (Pier- gest that the deposit was formed by fast loading of high-density son and Costa, 1987). These sedimentary characteristics of the sediments under overpressured conditions. This evidence im- Cacarajicara Formation are similar to those of deposits pro- plies that the member formed from a high-density turbidity sus- duced by a subaqueous eruption (White, 2000). Subaqueous- pension. eruption flow deposits are also composed of three layers; in Upper Lime Mudstone Member. The fine-grained Upper ascending order, these are a grain-supported high concentration Lime Mudstone Member was probably deposited from a dilute of rocks that is identified with high-concentration laminar flow, sedimentary suspension. The gradually changing grain size and a massive to stratified, graded, volcaniclastic sandstone layer composition from those seen in the Middle Calcarenite Member that formed from a high-concentration turbidite flow, and a fine- 142 S. Kiyokawa et al.

Fireball ejecta curtain Ballistic flow high-energy ballistic 100 km flow enters ocean gas-containing ? hyperconcentrated flow tsunami 0 dilute suspension wave?

2000 m collapse / erosion seismic wave Caribbean Sea Yucatán Platform hyperconcentrated flow Stratigraphic characteristics (high-density, turbulent flow) Upper Lime diluted material dilute fine sediment lower-density Mudstone Member suspension velocity profile high density turbulent Middle Calcarenite suspension deposits (homogeneous, turbulent Member fluid-escape structure) high-density suspension grain suspension cloud high-concentration, high-speed laminar-flow deposit Lower Breccia (reverse graded breccia, Member poor matrix, hydrostatic fragmentation) rip-up clasts high-speed laminar-flow erosion surface

Figure 14. Schematic sedimentation model of Cacarajicara Formation. Note that impact-related shock waves and ballistic flows created gigantic hyperconcentrated flow. Flow consists of three different flow units that formed three sedimentary facies sequences: high-speed laminar-flow clasts, high-density turbulent-suspension deposits, and low-density, diluted, fine material. Middle and upper sequences might have been affected by tsunami wave mixing.

grained tuffaceous layer that formed a dilute low-density sus- 1989). This suggests that the seismic shock wave and ballistic pension (Mueller and White, 1993). The subaqueous eruption flows arrived almost simultaneously. flows are products of high-energy flow and suspension depo- As described here, the Cacarajicara Formation is a high- sition in the deep sea. The stratified middle sequence of the energy flow deposit that was formed by platform collapse re- subaqueous eruption flow, however, is different from that of the sulting from an impact-related seismic wave and ballistic flow. Cacarajicara Formation, which preserves a homogeneous cal- This flow transported the shallow- (continental shelf) and deep- carenite sequence. The massive, homogeneous calcarenite se- water (continental slop) sediments of the Yucatan platform mar- quence of the Cacarajicara Formation has a more mixed and gin to the deep Yucatan ocean basin. As evidenced by the thick suspended character. homogeneous calcarenite, such a gigantic flow would have been One possibility is that an extraordinary gravity flow was very turbulent. An immense tsunami resulting from the impact triggered by an impact-related earthquake, keeping in mind that might have mingled with this turbulence to form the very thick the estimated collapse locality of the Yucatan platform margin homogeneous calcarenite sequence. is more than 500 km from the impact site. The arrival of the CONCLUSIONS seismic wave (at 5–7 km/s) would occur ϳ2 min after the arrival of impact ballistic flows (the initial blast is 30 km/s and The Cacarajicara Formation is a Ͼ700-m-thick calcareous main body of the vapor cloud is 10 km/s or less) (Melosh, sedimentary sequence that fines upward. This formation con- Cretaceous-Tertiary boundary sequence in the Cacarajicara Formation, western Cuba 143 tains Maastrichtian fossils (foraminifera), and impact-related Bohor, B.F., and Glass, B.P., 1995, Origin and diagenesis of K/T impact spher- shocked quartz and spherules. Three members are identified in ules: From Haiti to Wyoming and beyond: Meteoritics, v. 30, p. 182–198. Bohor, B.F., 1996, Sediment gravity flow hypothesis for siliciclastic units at this formation. The Lower Breccia Member consists of a matrix- the K/T boundary, northeastern Mexico, in Ryder G., Fastovsky D., and poor breccia sequence formed by high-energy lamina-flow. The Gartner, S., eds., The Cretaceous-Tertiary event and other catastrophes in Middle Calcarenite Member is characterized by well-sorted Earth history: Geological Society of America Special Paper 307, p. 183– homogeneous calcarenite that was deposited from a high- 195. concentration sediment suspension. The Upper Lime Mudstone Bourgeois, J., Hansen, T.A., Wiberg, L., and Kauffman, E.G., 1988, A tsunami Member is composed of massive, fine calcarenite-lime mud- deposit at the Cretaceous-Tertiary boundary in Texas: Science, v. 241, p. 567–570. stone, which was deposited from a dilute suspension. The grad- Bralower T.J., and Iturralde-Vinent M., 1997, Micropaleontological dating of ual transition between the three members of the Cacarajicara the collision between the North American Plate and the Greater Antilles Formation can be explained by high-energy hyperconcentrated Arc in Western Cuba: Palaios, v. 12, p. 133–150. flow. Alternatively, the upper half of the formation can be in- Bralower, T.J., Paull, C.K., and Leckie, R.M., 1998, The Cretaceous-Tertiary terpreted as a deep-sea tsunami deposit (homogenite) similar to boundary cocktail: Chicxulub impact triggers margin collapse and exten- that in the upper half of the Penãlver Formation. The presence sive sediment gravity flows: Geology, v. 26, p. 331–334. Bronnimann P., and Rigassi, D., 1963, Contribution to the geology and pale- of shallow- and deep-water facies clasts, shocked quartz, spher- ontology of the city of La Habana, Cuba, and its surroundings: Eclogae ules, and a south-southeast-trending paleocurrent suggest that Geologicae Helvetiae, v. 56, p. 193–480. this flow was formed by Chicxulub impact-related, seismically Dressler, B.O., and Sharpton, V.L., 1997, Breccia formation at a complex im- induced gravity flow combined with impact ballistic flow. pact crater: Slate Island, Lake Superior, Ontario Canada: Tectonophysics, Therefore, the Cacarajicara Formation is one of thickest se- v. 275, p. 285–311. quences resulting from the gigantic Chicxulub impact-induced French, B.M., 1998. 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