Calibration of Seismic Data from the Western Margin of Great Bahama Bank with Exposed Strata in the Maiella Mountains (Italy)

Eberli, G.P.*, Anselmetti, F.S.**, Bernoulli, D.**, Betzler C.*** and Van Konijnenburg J.H.****

*Comparative Sedimentology Laboratory, University of Miami **Geological Insitute, Swiss Institue of Technology, Zürich, Switzerland ***University of Hamburg, Germany **** Carbonate Team Shell, Rijswijk

Rationale for Study:

The isolated carbonate platforms of the Bahamas are often taken as a modern analogue for the interpretation of ancient platform deposits. Insight to the architecture of the banks is limited to seismic and core data. Ancient analogs can help interpret these subsurface data sets. The Maiella Platform is a superbly exposed platform with a similar evolution as Great Bahama Bank. A comparison of the seismic and outcrop architecture helps to better understand the stratigraphic architecture and sedimentary processes at isolated platform margins.

Little Bahama Umbria/Marche Bank M. dei Fiori FLORIDA Adriatic Sea 0 100 km Gran S asso ROMA Northwest Providence PESCARA 26 e rida Channel Miami el N ? Chann Maiella A A D ROMA Mt. SimbruiB Marsica 30o 30o CA PL Straits of Flo Northeast Providenc Gargano M ine Intern B ni A estern L Tongu Mt. Lep al all Y W EM Unda ochth Clino Andros ini CA Site 1005 Site 1007 Island e of the Ocean onous Site 1006 Site 1003 Exuma Sound units Matese A 24 N o o Cay Sal Tyrrhenian Sea 0 0 Bank B NAPOLI Great Bahama Quaternary volcanoes Bank Pelagic sequences (Umbria/Marche basin) 50 km Continental areas Marine areas (continental crust) Carbonate turbidites; slope- and CUBA base-of-slope sediments Major thrusts Carbonate platforms Ocean crusts Subduction zones Carbonate platform: Subsurface front of internal A: Maiella - Apulia allochthonous units 80 78 76 B: Lazio - Abruzzi

Late Cretaceous (84 Ma) paleogeography and Map of Great Bahama Bank with location The Maiella platform and the base-of-slope the location of the Bahamas archipelago (B) of wells and seismic data set used in this setting in the Gran Sasso area and the and the peri-Adriatic platforms (M). study. present-day position of the Apulia (A) and Key: A, Adria; B, Bahamas; CA, central Atlantic; Lazio-Abruzzi (B) platforms. In the Gran D, Dinarides; EM, eastern Mediterranean; Sasso area the base-of-slope section is M, Maiella; PL, Piemont-Liguria ocean; thrust into Mesozoic-Tertiary strata and Y, Yucatan. flysch, while the Apulia platform margin in the Montagna della Maiella is only marginally involved in the thrusting. Architecture and Facies of Great Bahama Bank

Western Prograding Margin Bimini BankStraits of Andros Andros Bank 0.0

0.5

1.0

1.5

2.0

2.5 s (two-way tavel time) 3.0

3.5

4.0

30 km

Questions: What is responsible for the chaotic facies of Bimini and Andros Bank? What is the facies of these banks? Answer: Taking the Maiella Platform as an analog, the facies is a horizontally bedded platform interior facies. The seismic facies is caused by low impedance contrasts in the strata that is below the signal/noise ratio.

Stratigraphy and Architecture of the Maiella Platform Stratigraphic architecture A View from the Maiella platform to the Maiella platformmargin Gran S assod'Italia base of slope margin and onto the slope sediments.

SSE NNW 1200 m 5a In the foreground is the Cretaceous 5 4 3 2 Santo Spirito Fm. 3 500 m 4 5a Venacquaro Fm. platform, which is onlapped along the Cima delle Orfento Fm. F. Gelata Fm. Murelle Fm. 3-5 M. Corvo Fm. 1 2 2 vertical escarpment by slope sediments. 1 Tre G scale rotte Scaglia Bianca Fm. 0 Fm. change Morrone di Pacentro Fm. 1 1L V a Cefalone Fm. The overlying uppermost Cretaceous lle d e F ll'In m fe . rn Maiolica Fm. 0 o 0 0 0 12 km 0 10 km sediments level the relief

B between platform and slope.

Time Stages Eustatic curve after in Ma SSE Maiella platform marginNNW SSE Gran Sasso base-of-slope WNW Haq et al. (1988) Series 10 The top of the mountain to the left is Serravalian 15 Langhian Bolognano Fm. Burdigalian Miocene deposits 20 Sea-level Rise Fall formed by Upper Eocene slope and Aquitanian 25 25 25.2 Chattian ?5a ?5a Venacquaro Formation 30 30 Rupelian ? ? ? 35 Oligocene reefal units, which 35 36 Priabonian SS5 40 40 Bartonian

45 45 Lutetian SS4 prograde over slope deposits. 50 SS4 50 Ypresian Formation 54 ? Santo Spirito Fm. 55 55 Fonte Gelata Thanetian SS3 SS3 60 Vertical relief from mounaintop 60 3 ? Danian

Paleocene Eocene Oligocene Miocene 65 65 66.5

Maastrichtian 70 70 Orfento Fm. M. Corvo Formation escarpment to the valley floor is SS2 75 75

Campanian 80 80 SS1 approximately 1200 m. 85 85 Santonian Cima delle SS1 Scaglia Bianca Formation Upper Cretaceous Coniacian 90 90 Turonian Murelle Fm. Tre Grotte Fm. Cenomanian 95 95 96 Valle del Cefalone Formation From Anselmetti et al. 1997 Inferno & 100 100 Bocca di Valle ? ? ? Albian 105 105 SS0 ? 110 110 Aptian L. Cretaceous Morrone di 115 Barremian Pacentro Fm. Maiolica Formation (A), chronostratigraphy and time space diagram (B) of the Maiella platform and the Gran Sasso base-of-slope (after Vecsei 1991; Eberli et al., 1993; Sanders, 1994; Mutti et al., 1996; Van Konijnenburg, 1997). The two areas are not connected and correlation is based on biostratigraphy and facies evolution. Numbers refer to the supersequences defined in the Maiella platform and the correlative units in base-of-slope setting in the Gran Sasso area. Seismic facies of platform, escarpment and onlapping slope and its outcrop analog

Great Bahama Bank Maiella Platform

0 SSE NNW Tertiary slope and 6 Prograding Margin ? 6 prograding units constructional margin 0.2 5 4 Santo Spirito Fm. 6 3 2 5 0.4 Orfento Fm. 3 4 Cima delle Basin Fill Murelle Fm. Orfento Fm 2 0.6 1 Platform 0.8 Escarpment Basin Fill 1 Tre Grotto Fm 0 Tre G rotte Fm. s (two-way travel time) 1.0 Slope/basin Morrone di Pacentro Fm. aggrading platfrom

1.2 Escarpment km 0 1356724 8 91011121314 Platform Interior Escarpment Slope and Basin The western margin of the buried Bimini Bank has Schematic cross-section across the Mailla Platform The escarpment is an undulating surface with an ave- an escarpment that separates transparent/chaotic margin displays the escarpment, onlapping basinal rage declivity of approximately 35 degrees. Horizontally seismic facies from onlapping continuous reflections. sediments and the transformation from an aggrading layered platfrom carbonates extend to the escarpment, Above the escarpment the plaform develops from an to a prograding platfrom. documenting erosion of the marginal facies. aggrading to a prograding platform.

The synthetic seismic model, Maiella Platform Effects of noise and amplitude gains Stratigraphyof the escarpment CMP NO. 1 2141 6181 101 121 141161 181201 221 241261 281 301 321 341 361 381 1 km time-window of displayed sections 0 0

200 200 Basin Fill 400 Time (msec) Orfento Fm

400 Time (msec) 600 Platform no noise - true amplitudes 10% noise - true amplitudes 0 Basin Fill 600 Escarpment Tre Grotto Fm 200 Platform Interior Escarpment Slope and Basin

400 Seismic Facies at 30 HZ: Time (msec) 600 no noise - time-ramp scaling 10% noise - time-ramp scaling Platform: Transparent to low amplitude reflections 0

Karstified platform top: Strong wavy reflection 200 Escarpment at Cima delle Murelle with onlapping 400 Slope: High-amplitude continuous reflections Time (msec) basinal sediments. Cliffs are megabreccias, forested

Reefs: Discontinuity in reflection, small patch 600 no noise AGC (100ms) 10% noise AGC (100ms) areas are periplatform and slope sediments. reefs fall below seismic resolution 0 200 The transparent facies of the platform interior is 400 caused by the low reflectivity that barely exceeds Time (msec) the noise levels. 600

The sequence stratigraphic significance of carbonate platform escarpments Ages across hiatus in escarpment Depositional Geometries Depositional Geometries Slope and Basin 66.5

Maastrichtian SS2 SS2 74.5

SS1 SS1 Campanian

84 Santonian and 88.5 Hiatus Coniacian Time Diagram Using Sequence Stratigraphic Interpreta True Time Diagram 91 Turonian Cenomanian 97.5 Ma SS0 Albian Platform 1 km SSB Ages document coeval sedimentation in the basin and on the platform Anselmetti (1994) Seismic facies of upper slope and its submarine canyons

Miami

Submarine F L O R I A D Canyons 200 m Western Line

Clino Unda Wedge of N Andros Drift Deposit 1006 1005 Island Straits of Florida 1003 1007

CAY SAL BANK 1008 GREAT 1009 BAHAMA Nicholas Channel BANK

10 km ~100 m CUBA N Vertically exaggerated three-dimensional view of Pliocene slope topography with Location map of Bahamas Transect canyons that run perpendicular to and seismic survey area (black box). the shelf break into the Straits of Florida 1 km 550

Canyons in slope Transparent seismic facies consists of fine-grained periplatform ooze Seismic facies of slope is

high amplitude ms (twt travel time) and discontinuous

850 Seismic line along strike displaying submarine slope canyons on upper Seismic line along Bahamas Transect displaying slope slope with cut and fill geometries but the facies of the fill is not known. facies and canyon cuts. Comparison to geometry and facies of Cretaceous canyon fills, Maiella

SW Great Bahama Bank NE 2662 N Oligocene Mte S.Angelo 2669 m 0.7

U. Eocene 2500 m 0.8

2500 m 2400 m 0.9

U. Paleocene 1200 m m 1200 1.0 2400 m Camp.-Maast. two-way travel time (sec) travel two-way 2300 m a) 5 km 2300 m U. Eocene b) c) 700 m 700 m U. Paleocene a) Middle Miocene (Langhian) channel in the western slope of Great Bahama Bank with cut and fill geometry. b) Upper Paleocene (upper Thanethian Ð upper Ilerdian) channel in Upper Cretaceous slope sediments of the Maiella platform. Channelization occurred in stages, producing a cut and fill geometry with redeposited carbonates. The channel is overlain

by Upper Eocene (Priabonian) slope deposits that form a recessive scree slope. Cliffs at the top of the slope are Oligocene 50m reefs. Dashed line indicates a plane of an Alpine fault. c) View from southwest into Maiella channel displaying the cut and fill geometry of the infilling strata. The base of the channel is concave downward. The top is nearly flat as calcirudites and B grainstones fill the incision. D) Close-up of channel fill. A carbonate mega-conglomerate of Cretaceous platform clasts with large boulders up to 5m in diameter is deposited at the base of the channel. Amalgamated litho-bioclastic conglomerates d) and coarse carbonate turbidites fill the channel axis. The turbidites thin upward and interfinger with fine-grained limestone. Slope and Basin adjacent to Great Bahama Bank Seismic Facies

350 700 Platform SB SB Upper slope Cyclic shallow-water Middle to carbonate deposits m Lower slope Fine-grained prograding

600 lobes, canyon incisions ~

Toe-of-slope TWT (ms) Fine-grained sediment, turbidites TWT (ms) Basin small-scale channeling HST LST Redeposited carbonates, Cyclic deep- coalseced mounds, hemipe- water deposits and drift deposits lagic background sediments 2 km ~ 10 km 720 820 Discontinuous to chaotic facies overlain Transparent facies of unconsolidated slope by continuous high-amplitude reflections 2 km material; high amplitude incisions 1240 800 940

1 TWT (ms) TWT (ms) TWT (ms)

1610 1550 1300 1 Low-amplitude, highly coherent of drift Mounded moderate amplitudes at levees, chaotic to Discontinuous high-amplitude channelized deposit; 2 wavy to discontinuous sand waves transparent facies in channel middle to lower slope

Architecture of Seismic Facies

WSW Santaren Channel Site 1004 Great Bahama Bank Clino Unda ENE Little Bahama Site 1006 Site 1007 Site 1003 Site 1005 Bank FLORIDA 00 0 100 km Northwest Providence 26 Channel Miami Florida N Channel 0.50.5

Straits of e Northeast Providence in L rn Pleistocene/Holocene te es Tongue of the Oce WUnda Clino Andros Site 1005 Site 1007 Island Site 1006 Site 1003 Exuma 1.01.0 Sound 24 Pliocene Cay Sal an Bank

Platform Great Bahama 1.51.5 Bank Miocene msms Slope CUBA (twt)(twt) Base of Neogene Drifts 80 78 76 10 km Prograding clinoforms interfingering with drift deposit Dip-section through lower slope turbidite packages Strike-section through lower slope turbidite packages N S

sea bottom multiple sea bottom multiple

twt Site 1007 SW (ms) Site 1004 Site 1007 Site 1003 Site 1004 Site 1005 NE 1400 700 twt Site 1006 Site 1007 Site 1003 Site 1005 300 twt (ms) sea floor B (ms) 200 C 900 sea floor 500 400 A 700 D B 600 E

C ? D E 800 900 F

F sea floor E2 G G B H sea floor H C CI B 1000 I 1100 I C K D L E 1200 D K E 1300 L F 1 km M G PT F N 1400 H O I turbidites M G H K slump deposits 1500 I P L N K 1600 O L 1600 M M ve » 6.8 X N P N ve » 7 X 1800 1700 drift deposits O ML O CR 1 km turbidites slumps P P Seismic line 106 and line drawing with Lower slope and toe-of-slope along seismic line Cross line at Site 1007 in a strike direction, interpretation. Grey stippled area outlines 106 with line drawing and interpretation of displaying the lobate geometries of the drift deposits. geometries of turbidite and slump packages and turbidite and slump packages. associated faults. Base of slope facies in the Gran Sasso area

Channelized redeposited carbonates in the Monte Corvo Formation Umbria/Marche M. dei Fiori Adriatic Sea

Gran S asso ROMA PESCARA

Maiella A ROMA Mt. SimbruiniB Marsica Gargano Internal allochthonous units A M t. Lepin

Matese A N Tyrrhenian Sea

B NAPOLI

Quaternary volcanoes

Pelagic sequences (Umbria/Marche basin) 50 km Carbonate turbidites; slope- and base-of-slope sediments Major thrusts Carbonate platform: Subsurface front of internal A: Maiella - Apulia allochthonous units B: Lazio - Abruzzi

Location Map of the Gran Sasso area.

Prograding basin-floor turbidite fan complex see below

entation

Pelagic sedim o 2-5

S E

W N

Minor contour current activity

Depositional model for the basin floor turbidites in the Panoramic view of the eastern side of Monte Corvo. Monte Corvo Formation: in the lower part, thick-bedded bioclastic turbidites with a low-angle positive relief and associated Gran Sasso Basin. onlap geometries (white arrows), are overlain by sheet-like intraclastic breccias (b). The upper part of the Monte Corvo Formation consists of stacked, channelized intraclastic breccias (outlined in white) and calcarenite turbidites. The boundary between the Monte Corvo Formation (here lowermost Danian) and the overlying Fonte Gelata Formation shows no major erosional relief although it is associated with a major hiatus. The same is the case between the Fonte Gelata Formation (here Upper Paleocene to Middle Eocene) and the Venacquaro Formation ("middle"-Upper Oligocene).

Close-up from the overview photograph, displaying the Channelized trubidite lobe of the Monte Corvo Formation. Discontinuous seismic facies of the lower slope in western Great erosional downcutting of turbidite lobe into basin sediments. Bahama Bank is likely the seismic expression of the channelized lobes of turbidites seen in the Gran Sasso base of slope.

Summary Transparent, low reflectivity facies of the platform interior is the result of low impedance contrast in horizontally layered platform carbonates. Platform escarpment produces good seismic reflection despite its steep declivity, because of the high impedance contrast between the platform and onlapping basin sediments. Deep incised channels on the upper slope are a common feature of steep-sided carbonate slopes. Their filling consists mostly of coarse-grained platfrom material. The high-amplitude and discontinuous seismic facies of the lower slope and toe-of -slope is a direct result of the redeposition processes and the lobate nature of carbonate turbidite sequences. The high-coherent and low-amplitude seismic facies of the drift deposits is a result of low impedance contrast but large lateral homogeneity in these deposits. Wavy facies in the basin axis documents traction currents.