Page 5 - Ragg_et_al-1999-Tectonics

RAGG ET AL.: TECTONIC STRESSIN SICILY 673

w SanBartolo Carrubo Cozzo Bimmisca Cassibile Capo E
(5) Negro(2)
Scalia(4) (3) (1)
-o

I ,I0 180

-0

--

o 18o

\ 180.• -_•--_M- aralsncdhalks

.'].'.] Evaporites

0 180 •'• Marls

Breakout 180 0 180 •-• (PMacktCsito.lniemsa-gnirRtadiinastgonFuesmsas.)

••o o Breccia

v• Rudisltimidestones.

• Cherrmyarllyimestones -0
• (AmerilloFm.)

-••-] M(HarlyylbiFmlmeasto.n)es

• Wackestones

Volcanics

;;;• (pyrocloasratlitcesrbeadsalts)

-•_• cClaoysnaltderendanetisnewwgeiptadhltimmeerastraolnnsesd

Black shales

=-•----(-S• treppFemn.o) sa

• Dolomites

Figure4. Stratigraphbyre, akouotrientatioanndbreakouotccurrenfcoerthewellsCassibil(ewell1),Capo
Negro(well2), Bimmisca(well3), CozzoScalia(well4), Carrubo(well5) andSanBartolo(well6) locatedon

the Hyblean Plateau.The severevariation in the deducedbreakoutorientationof the well Carrubocan be

assumebdedueto tooldamageN. otethatbreakoutnsacenceunderanangleof 90øto thedirectionof SHmax

(see text).

downfaultingthe Hyblean carbonatesby severalhundred strikesN75øE(rosediagramin Figure9). A secondorientation

meters westwards. Although they exhibit the same is nearlyorthogonaalndstrikesN135øE,roughlyparallelto

stratigraphoyf theelevatedHybleanPlateaut,heyhavebeen thedirectionof themeanstressorientatioonf westernEurope
ascribedto the foreland becauseof their location within the andperpendiculator the strikeof the GelaNappe.The third

westerncollapsedmarginof the plateau.Sincethe breakout trendstrikesN35øEin the directionof the openingof the
orientationscatterwithin the individualwells, we conclude Pantelleria Rift.

that there is a low-stressanisotropyin the southwestern The wells Simeto(well 16), Dittaino(well 17), andChiesa

segmenotf theGela-CataniFaoredeep. (well 18) are locatednorth of the Hyblean Plateauin the

To checkwhetherthereareprominenttrendsin thebreakout CataniaPlain (Figure 1). In the well Dittaino no breakouts

orientationosf the foredeepw, e havecombinedthe individual occurredandit is thereforenotconsidereadnyfurther.Thetwo

breakouotrientationfsromthe five wells(wells7-11) into otherwellsdisplaya NE trendingSHmaxorientatio(nFigure
onerosediagram.Despitethelimitedmeaningof theSHmax 6). Bothwellsdo notreachthe Hybleancarbonatesuccessions

direction from the breakout orientationsin the individual but cut throughthe Plio-Pleistoceneclays which fill the

wellst,hecombinationfthefivewellsintoonerosediagram foredeep.

indicatesthree dominanttrendsof SHmax. One orientation The NNE to NE orientation of SHmax obtainedin the wells