The pinnacle reefs ofJabaloyas (Late I{immeridg¿an, NE Spain

The pinnacle reefs ofJabaloyas
(Late I{immeridg¿an, NE Spain):
Vertical zona[ionand associatedfacies related
[o sea level changes
M. AUREIi. and 13. BÁ])ENAS
Departamento de Ciencias de la Tierra,
Universidad de Zaragoza, 50.009 Zaragoza, Spain
ABSTRACT
Tite outcrops located near Jabaloyas (Northeast Spaln, Iberian basin)
allow the reconstruction of tite sedimentary environments of a late Kimmeridgian carbonate ramp. In tite middle ramp arcas, aboye storm wave base level, grew a set of reefs which generally display a pinnacle geometry. The fabrie of these reefs consists of different proportions of colonial forms (mainily
corals), internal sediment and microbial crusts to associated encrusting organisms. Four pinnacles have been sampled along a 6 Km proximal-distal section across thc ramp. Tite relative proportion of corals and microbial crusts
evaluated in titese samples allows to diffcrcntiate between coral titrombolites
and corál-mierobial ernst reefs fabrica. Changes in thesc fabrica allow to define some vertical and lateral zonation in the pinnacle recfs. Tite variation of
tite fabrics in the pininacle reefs and tite transition between the different associated facies have been related to sea level changes. An iitial fast rise of sea
level resulted in botit the drowning of the mid ramp grain-supported facies
and in tite grow of scattered coral thrombolites. Tite aggradation of tite pinnades, with increasing proportion of metazoan builders, was initiated and/or
followed during the continuous riscr of sea level, and coeval carbonate sedimentation recovered in tite inner arcas of tite middle ramp. The total risc of
sea level was between 12 to 15 m. During a subsequent stillstand of sea level,
tite successive observation of aggradational and progradational stacking patteras in tite coevally developed inter-reef facies allows tite diflerentiation of an
early and late highstand systems tract.
Key wnrds: Late Jurassic, Iberian basin, carbonate ramp, reef, sea level
changes
Cuadernos de Geología lb4ñ ca, mini. 22, 37-64.
Servicio de Publicaciones. Universidad C<>rnplutense, Madrid, 1997.
38
Al. Áu,-clI y B. Bádenes
RESUMEN
Los afloramientos localizados en las proximidades de Jabaloyas (Cordillera Ibérica, Teruel) han permitido reconstruir los distintos amiñentes sedimentarios de la rampa carbonatada del Kimmeridgiense superior. En las parLes medias de esta rampa, sobre cl nivel de base de oleaje de mal tiempo, tuvo
lugar el crecimiento de una serie de arrecifes alsíados, que generalmente presentan morfología de pináculo. La fábrica básica de estos arrecifes está formada por diferentes proporciones de formas coloniales (corales en mayor
abundacia), sedimento interno y costras microbianas, que incluyen organismos encostrantes asociados. Se ha evaluado la proporción relativa entre estos
componentes a partir de cuatro pináculos, localizados en los diferentes dominios de sedimentación. Los cambios en la fábrica arrecifal permiten definir
cierta zonación vertical y lateral en los pináculos arrecifales. Se han relacionado las variaciones en las fábricas arrecifales y los diferentes cambios en las
facies asociadas, con sucesivas variaciones del nivel del mar. Una etapa inicial
de ascenso rápido del nivel del mar implicó ia estabilización (le las facies granosostenidas interarrecifales, así como el crecimiento local de arrecifes doniinados por costras microbianas. El crecimiento vertical de los pináculos, con
un predominio de las formas coralinas, se inició o continnó durante esta eta-
pa de ascenso <leí nivel del mar, que también permitió la recuperación de la
sedimentación carbonatada en las zonas más internas de la rampa. El ascenso total del nivel dcl mar durante este intervalo fue de 1.2 a 15 m. En la etapa siguiente de estabilización del nivel del mar, la observación sucesiva de geometrías agradacionales y progradacionales, ha permitido diferenciar entre
los cortejos dc alto nivel del mar temprano y tardío (early and late higitstand
systems tract).
Palabras clave: Jurásico, cuenca Ibérica, rampa carbonatada, arrecifes,
caminos del nivel del mar.
INTRODUCTION
The growth of organisms that construct reefs is controlled by factors like
xvave energy, 1)ackground sedimentation, nutrient supply or oxygen fluctuations. Because some of these factors may change with depth, tite internal variation of the composition and fabric of tite reefs may reflect variations in sea
level. TIle interplay between reef and carbonate platforrn growth and sea le‘e’ vhdl
lid.> uve’’ i epuí LW ni >evei di »luutc> ~
rWllUdIl
dliii CUU1d~Ci
198i; James and Macintyre, 1985>. Tite resulting data have been applied to
the geological record to define sea level cycles of d¡ffercnt order and magnitude. To aclíjeve reliáble reconstructions of sea level cycles, a precise control
Tite pinnacle reefl oflabaloyas <Late Kimmeridgian, NF Spain)
‘39
on the vertical and lateral distribution of facies on ancient carbonate platforms is needed. If recfs are cocvally developed on these platforms tite study
of tite variation of tite reef fabric may provide independent control of sea level changes.
Tite Sierra de Jatalón <Iberian Chain, Teruel province, northeast Spain>
offers nearly undeformed and continuous outcrops, wbich include a set of
Late Ki mmeridgian patcit reefs. Titese reefs ivere developed in tite shállow
areas of a low-angle carbonate ramp. Most of them are 12 to 16 m itigh and
display a cylindrical to conical sital)e, with very steep slopcs. Based on titis
rnorpbology, early studies by Geyer (1965) and Giner and Barnolas (1979)
described them as pinnacles. Fezer (1988) and Errenst (1990a,b) provided a
more detailed studv of these reefs, especially on their coral fauna and associated facies. Further data ori tite composition, morpliology and stratigrapiti-
cal and sedimentological context taese reefs, have been provided by Leinfelder (1993), Leinfelder et al. (1993,1994), Nose (1995) and Baumgiirtner
and Revle (1995). Tite results reported on titese works, wliicli inelude detailcd descriptions of tite reef fabrie and discussioiis ábout tite factors which controlled tite origin and development of tite Upper Jurassic iberian reefs, have
provided the basis for our analysis.
The outcrops ]ocated near Jaibaloyas allow tite reconstruction of a 6 Km
long cross-secti.on, witich extends from inner to mid ramp areas. Four l)innacíe reefs tiave been sampled along titis seetion, establishing their vertical zonation hased on the variation of the proportion between microbial crusts and
metazoan builders. In addition, tite lateral and vertical distribution of the differení inter-reef facies bave been studied. Tite main aims of titis paper are: (1)
to propose a preliminary model, showing tite overalí vertical and lateral zonation of these reefs; (2) to place tite reefs in tacir sedimentological contcxt
b íntcrpretmg tite associated facies; (3) to relate tite initiation, development
and deinise of tite pinnacle reefs and associated facies with tite related sea level changes.
GEOLOGICAL AND STRATIGRAPH1CAL SETTING
Tite Iberian Citain, a montainous system located in the northeastern part
of the Iberian Peninsula, contains well-preserved and continuous outcrops of
Mesozoic sedimentary rocks. The Upper Jurassic outcrops of Jabaloyas are
located Southeast of Teruel (Nortiteast Spain), in tite western-central part of
the Iberian Chain (flg. 1). The reef studied were developed in marginal areas of Ile so-called Iberian basin. Marine sedimentation in the lberian basin
took place in shallow and extensive carbonate ramp settings (several hundreds of kilometres across) during Late Jurassic times. Titese ramps were
open to the Tetlíys sea to thc East. 1 lowever, during major flooding episodes
40
M. Aurelí y 8. Bádenas
N420
Fig. 1 —Location of Ihe studied aiea and distribution of tbe upper Jurassic outcrops between
Frías and Jabaloyas localities. The lower inset locates the five sections studied around Jabaloyas.
Fig. 1.—Situación del área estudiada y distribución de los afloramientos del Jurásico superior
entre Frías y Jabaloyas. La parte inferior muestra la situación de los perfiles estudiados en torno
a Jabaloyas.
The pinnacle reefs ofJabaloyas (Late Kimmeridgian, NE Spain)
41
conneetion with the boreal realm was possible aeross the so-caiUed Soria Seaway to tite Northwest (Aureil and Meléndez, 1993).
The main lithologies and stratigrapliic distribution of tite Kimmeridgian
sedimentary rocks of Ile Sierra tite Jabalón, between tite Arroyofrío and Jabaloyas localities, is shown in Fig. 2. The lower marly unit corresponds to tite
Sot tite Chera Formation and spans from Late Oxfordian to Early Kinnerid gian. This unit changes offshore to Ile rhythmic mudstone and marí alternations of tite Loriguilla Formation. The sandstones and ooliIlic gralnstones of tite Pozuel Formation prograde aboye titese units (AureIl, 1990; Bádenas and Aurelí, 1997).
The topmost Kimmeridgian unit includes tite reefal unit studied in titis
work. Based on titeir mieropalontological contení, Fezer (1988) dated Ile
studied reefs and associated facies as Late Kimmeridgian. According to Nose
(1995), they belong to tite the lowermost Late Kimmeridgian biozone (i.e.
acantbicum biozone). Lititostratigraphically, they have traditionaily been assigned to the Higueruelas Formation. 1lowever, according t() both its lithology, its fossil content and its lateral equivalence witit tite offshore micrites of
the Loriguilla Formation we propose tite use of Ile term Torrecilla Formation br Ibis reefal unit (Fig. 2>. Tite Torrecilla Formation is a Rlmmeridgian
reefal unit, defined by Alonso and Mas (1990) in the north-western part of
the basin.
A sequence boundary below tite Torrecilla Fm. is indicated by a significant backstepping of facies (Aurelí, 1990; Fig. 2). In earlier works, we correlated this sequence boundary with the unconformity which is found offshore
between the Loriguilla and Higueruelas Formations (Aurelí, 1990; Aurelí
and Meléndez, 1993). This boundary was developed during tite Early Tithoman. However, Ile precise dating reported by Nose (1995) makes unlikely
tbis assignment. Consequently, the studied reefs are located in Ile iower part
of a depositional sequence witich spans from Late Kimmeridgian to Early
Tititonian. This sequence would corrcspond to tite upper part of tite Kimmeridgian Sequence used in our previous works, and is also recognized in noiiitern areas <i.e., Facies Association II and III in Bádenas et al., 1993, Ricla
outcrops). A third order sequenee boundary below tite studied recís has been
also proposed by Nose (1995) and Baumgíirtner and Reyle <1995).
OVERALL FACIES DISTRíBUTION
IN THE TORRECILLA FORMATION
The Torrecilla Formation reacites a maximum tbickness of 72 m eastwards, ni Ile Barranco de las Balsillas section (see BB section in Fig. 2). To
Ile West, the upper part of tite unit is partly eroded, and is unconformably
overlain by Albian fluvial sandstones (i.e. Utrillas Formation). Tite lower
42
ca
ca
¡‘u,> pe!pn4s
Al. Ani-oíl y B. Bádenas
4
D
O
o
ir
Ii
‘4
fi
II
E
1
‘4
>1
4
1
<0
o
1-
o
u,
.0
ÍD
E
e.
Fig. 2—Stratigraphy of the FQimmeridgian between Pie Arroyí>frftí iríd 4 aL.>al >vis 1<xr,lities (see
Fig. 1 for location of the correlated sections).
Fig. 2. —Estratigrafía del Kimmeíidgiense entre Arí-oyofrú> y Jal.>aloyas (situación de perfiles en
laFig. 1>
The pinnac-le reefs ofjábaloyas (Late fúnuneridgion, NF Spain)
43
part of thc Torrecilla Formation consists of marís and burroxved sandstones
witb aibundant plant remains, deposited in transitional lagoonal environments. Two cyclic parasequences, including levels wiIl pinnacle reefs, are
identified in Ihe more eastern complete sections (Giner and liarnolas, 1979).
Tite resuits presented in tliis work are based on a facies analysis iii dic lower parasequence, which has been preserved of the Early Cretaceous erosion
along 1w studied outcrops (Fig. 2). Tite facies analvsis is hased on tite measurement of five key sections (see Mg. 1 for location) and tite lateral tracing
of tite main distinguished facies associations. From proximal western arcas Lo
distal castern ones, these sections are narned: Fuente de la Toba (FT), Barranco del I)iablo (ED>, Barranco cte Ja Hoz <EH), Barranco de la Canaleja
(1W) and l3ar¡-aneo de las l3alsillas (BE). The correlation of the studied sections ~u1(1tlíe latera! and vertical disíribution of the main facies associations
distinguislied in 1.1w lower parasequence is shown iii Fig. 3. The pinnacle reefs inc.li.íded iii diese sections were sampled from bottorn lo top. The pi-opor¡ion l)eLweeiI tite different components of tite reef fabrie ~vasestablislied bv
jjoinúcoiinting along thín sectíons. Three main facies associations have been
distinguislíed: rectal facies, inter-reef facies (A,13,C) a..nd tli.e topmost post-reef
facies 1).
IIEEFAL FACIES
‘111w n-iorphoiogy aud Lite fabrie of tite reefs of Jabaloyas has been descriI)ed by Fezer (1988), Errenst (1990a,b), Leinfelder et al. (1993, 1994) and
Nose (1995). Titese works include the identification and description of tite
diffcrent fossils aud titeir distribution along Ile reefs. Below, we outline tite
main features ol)scrved in the rectal facies.
Moíwi I(IWC’ OF
i-4vvl~S
Tite studied parasequence includes seattcred patch reef with variable
morphology. Most of t.bem have a írinnacle morphology and are distributed
in a discrete hoí-izon, from the ED to tIic BE sections (Fig. 4). Wcstward. in
Uhe FT section, tite pinnacles are absení and tliey laterally grade to a set of
m.etric patcli recta The pinnacles have a it.eight/widtb ratio close to 1 and
‘¡el-y steep slopes, more Ihan 450 The local coalescence of Lhese pinnacles
may result in reefs some tens of meter iii heigbt. Tite highness of dic pinnacies iw.reases eastward, with maxhnum vertical development in tite 1313 sitetion, wííere they can reach 16 m. Aronud Litis outcrop, metrie patch reefs are
also laLcrally found to tite top of tite pinnacles. l3etxveen the 1W and thc ED
sections, me pinnaeles are generally up to 12-13 m high. Locally on some of
44
Al. Aurelí y 8. Bádenas
V.g. 3.—Facies distribution iii the studied parasequence (see Fig. 1 fo>- location).
~g. 3.—í )istrib»íción de facies en Ea parasecuencia estudiad-a (situación en ]a Hg. 1
TIre pinnade reefs ofJabaloyas (Late Kimnmeridgian, NE Spain)
45
Fig. 4—Facies distribution in the BI 1 outcrop. The boundary between facies A asid C is an encrusted asid bui-rowed surface tlhat can be traced np into tire pinnacle core (i.e. 52 surface). The
distribufion of Pie samples in the Bit piimacle is also shown (tire topmost sample J is out of tibe
scope of tire photograph). See text for facies explanation.
Fig. 4—Distribución de facies en el perfil 1311. El limite entre las facies Ay C es una superficie
bioturbada y encostrada que se puede prolongar hacia el interior del pináculo (superficie 52). Se
muestra asimismo la distribución de las muestras analizadas (la muestra J queda fuera de la fotografía).
46
Al ..~ 1 ¿<‘vil y U. Badenes
/v >‘~>V
y,
~
8-
-—
FACIES O
____
FACIES C
FACIES A
Fig. 5,—Facies aud sampie distributhirí in the BC outcrop. lSelo~v tlíc st,sd cd
1>innacle. a intelí
ecl with a stratal niorj>hology is observed. See Lext br facies explana[i<n>.
Hg. 5—Distribución de facies y de muestras en cl perfil SC. Por ¿1 eI>ajo de.L pináculo se olJseIva
>a u k a rut ifal cía 1 gen metía bbíd ay - ‘Ver leyte para a explicación de 1vícii’s.
Th e pinnade reefi ojjabaloyas (Late Khnniehdgian, NR Spain)
47
PÁg. 6—Facies mxl sample distribution in Wc UD outcníp. Two prominent disa>ndnuities (le.
Sí and 82 surfaces) are found ja Wc pinnacle core. See text for facies explanation.
Fig. 6—-Distribución dc facies y de muestras en el perfil UD. l)entro del núcleo del pináculo se
reconocen dos superficies de discontinuidad (superficies SI y 52). Ver texto para la explicación
de facies.
48
M. AureIl y E. Bádenas
these sections (cg., BC section, see Fig. 5>, small biostronws up to 3 ni thick
are found below Ile pinnacles.
Fíat and sharp surfaces occur in the core of tite pinnacles. An upper surface, located 8 to 9 m aboye tite bottom of Ile reef is recognized in boIl the
BD, BH and BC pinnacles (see S2 in Figs. 4 and 6), whereas a lower surface,
located sorne 5 ni aboye tite bottom is recognized lii Ile more western pinnaeles, located around Ile BO outcrop (see Sí in Fig. 6).
Ti ni I4EEF FABIuC
The basic reef fabrie consists of variable proportions of boIl colonial
forms (mainly corals: 5-60%), microbial crusts and associated encrusters and
microencrusters (10-80%) and internal sediment <15-40%), giving risc lo framestone textures (Hg. 7). Other orgainisms such us lithophagid bivalves, gastropods and echinoids are common throughout Ile reef. The different proportions between colonial forms and mierobial crusts allows to separate two
reef types (based in the classification of Leinfelder, 1993): (1) coral-microbial
ernst reefs (refereed here as coral reefs), when tite proportion of colonial
forms is larger titan tite proportion of microbial crusts, and (2) coral-bearing
titrombolites <refereed here as coral titrombolites), composed of microbi al
crusts with a considerable amount of reef macrofauna (np te equal proportions of metazoans and crusts).
1. Colonial forms: Leinfelder el al. (1994) and Nose (1995) have classified
these red as coral-chaetetid-stromatoporoid microbial ernst recis. Tite dominant colonial forms are corals and, in much lower abundance, stromatoporoids, chaetetids, solenoporarean algae and sponges (malnly «lithistid» demosponges, according to Nose, in Leinfelder e! al., 1994). The corals include a number of different massive, itemispiterical and branching species. They
normaily occur as centimetrie lo decimetrie debris. Locally, large branching
eorals are found in growth position. According to Nose <1995), tite dominant
coral taica are Thamnasteria aud Microsolena. PAso frcquent are Galamophylliopsis, Stylina excelsa, Ovalasírea delgadol, Milleporidiumfin-mosum,
Chae! eles chabaisensis and Solenoporajurassica.
2. Microbial crusís: A dense micritic to peloidal (packstone) crust is found
around Ile colonial forms. This crust may also form tmportant volumes of
tite reef framework. Tite fabrie on titese crusts is mostly clotted and display
ini irregular growing with comnion domal morphologies. A particular crust
type deseribed by Scitníid (in Leinfelder e! al., 1994) for tite base of tite Jabaloyas ree! is represented by «downward facing nodular hemispheroidsí>.
Tite microbial ernst comprise variable proportions of boIl micro-encrusters,
ineíuding «Tubiphytes» morronensis (see diseussion iii Schrnid, 1995), Kosktnobullina socialis, Lithocodiwn, Bacinella, Thaumaloporella, Placopsilina,
TIre pinnacle reefs ofjabaloyas <Late Kiinmeridgian, NF Spain)
49
y,
-.
4
.4
Intsrnaj sdlment
Type 1 cav>t es
Type 2 caví e>
-
a,
‘
“
-
Nicrobial
Encr,ntecs: TbK- Koskinobullhría
Tublphytes
B- Bacinolís
Le- Lithocedlum
Th- Thaurretoporelia
Sp- Serpulid
A- Calcareous algae
Fig. 7.—Example of tire reef fabric, showing tire distribution of different encrusting organisms
(sample D in the 131-1 pinnacle>.
Fig. 7—Ejemplo de fábrica arrecifal, en el que se muestra la distribución de diversos orgarúsmos incrustantes (muestra D del Pináculo 21-1).
50
Al. Aurelí y Li Rádenas
and larger encrusters like serpulids or bryozoans (Fig. 7). Thcy usually form
less than 10% of tite total volume of the rock. However, witen tite fabrie 18 dominated by microbial crusts, Iley can reacit up to 20%. In these instances, tite
d iversitv of micro-encrusters is lower, being dominated by «Tubifhytes» morronensis. Botb tite microbial crusts and tite metazoají builders are largely bored by lithophagid bivalves.
3. Infernal sedimení: Two types of internal cavities are distinguislíed (Fig.
7): (1) type 1 cavities correspond to tite holes lcft during tite growing of both
colonial forms and microbial crusts; <2) type 2 cavities were origiriated 1w the
biocrosion and boring of the metazoan builders or the microbial crusts. Tite
cavities are generally filled by internal sediment. The internal sedimeuL
mosth’ consists of silty biomicrites (mudstoncs to wackestones), wilb scnttered debris of bivalves, echinoderms, gastropods, bentlíic forams, coralsand
microbial crusts. These niicritic fillings may be interrupted by tibe growiríg of
microbial crusts at several leveis. Grain-supported facies (i.e. peloidal aud
noidal packstones-grainstones) may also occur as interna) sediment. Bot.h
grain-supl)orted and micritie facies may be associated, formirig graded and
1 arninated structures in geopetal fillings.
GENERAL. [REN[)S (IP VERTICAL ANO LA-rERAL. ZONATION ON REIEFS
Four pinnacles regu.larly distributed in a proximal-distal ramp section
have been sampled in order to evaluate tibe general trend of tite vertical aud
lateral variation on tite proportion between colonial forms and ruicrobial
crusts.
1. Rl) pinnacle: Tite distribution of tite studied samples mvi the location
of tííe two planar surfaces along the core of the BD pinnacle is sbown in Fig.
6. Tite vertical variatiotí of the proportion of both colonial fornís aud mitrobial crusts (cf/mc ratio) is reported iii Fig. 8. Tite reef shows an overail upxvard increase of tite cf/mc ratio. Proportions of microbial crusts (45-75%)
are larger than colonial forms be]oxv Sí. The cf/mc ratio ranges froní 1.5 Lo
4 l)etween Sí and 52. In Uds zone, an important volume of the internal sediment contains ooidal particles, similar to LLe ones located in tite inter-reef
arcas (facies B, see below). Aboye 52, tite internal sediment is micritie and Ile
cf/mc ratio 15 larger titan 2.5.
2. 1311 pinnacle: ‘¡‘he distribution of tite studied samples in the BM pumaele is shoxvn in Fig. 4. Tite results reponed in Fig. 8 sitows overalí volumes of
colonial form between 40-70%, clearly larger titan microbial crusís (generally
below 30%). 1 loivever, Hiere al-e two arcas xxntit larger proporlion of mitrobial crusts: tite bottnm of Uae pinnacle (sample A) and Ile zone located
around tite 52 surface (sample G>. The cf/mc ratio is also differentbelow and
aboye tite 52 surface. i.e fi-orn 1 .3 to 3.2 and larger titan 6 respcctively.
Tlic pinnacle recj oJ jabaloyas (Late Rhntneñdgan, NR Spain)
nioroblal c,usts
-
]
51
ooi.io,mu/mIor.oruat
100%
A-
,1
50
0’
0
50
100%
-5,
10
2
e
o
¡
FACIES
A
2
FACIES
A
~
•~‘1
[~Bo
¡E
50
100
-
o
=48
Ñtfr ti
4
0
2
n,
0
A
o
¡
1~
1
Vi =~~Z~””’
oit osí o rE [líe paipo <ti» ti of col 00H11 fo rius ríd mi» olii =1Ci £ st
(¡<it Ii <Iín=4 is
vii [lic fo tu sounp Lcd porou ¡cíes. boiser! un p» >11 itA o»mU u»~ =Loííg tIno scc tíoos
1 ‘~Áurne of the íeef fiolíricí. 11w c=olurnuslot fluí to tu» igin show; Itt ‘sE 1
tic <u u o It¡ti» mí fi th oit o between colonial, 6 ~,ms and mocí-obí o] rEísts
g 8
\ tu w ion 1—tIcal de la p roporuidii de [orinas col o ni’ des x costr E mi i ola Ir> ES (mclii
otto los o rif,E [¡¡Sm»os cncost rolpIes is» >cioid 05> cl] los iii it,»> pinacu lo, sto di do ti, íd o en on
[<0w
tIc pu titos tu laminois delgadas <cl 04=se ha referido od ‘sol uiuelu totd dc lE fabrw E Erro » íf ol)
1 o colurnn,is loe úuio»doos a loo derecha muestran lo, ev >1 ucino ci-tic El di 1 líroluoreron cutre ha
iii Es OlOlilEl> 5 ‘1 custras microl¡iaiiois.
ji
sot í oto >1 iii ¡ u sIc ¡ s)
~o rclcrs tu fbi tot
52
M. Aurelí y B, Bádenas
3. BC pinnacie: Like in tite previous pinnacles, titere is an overalí upward increase of tite cf/mc ratio, only interrupted by samples F aud H (52
and 39% of microbial crust respectively). tite latter located on 52 siírface.
‘rite biostrome located below tite BC pinnacle was also sampled (sample A,
Figs. 5 and 8). Samples A and B show a close to 0.5 cf/mc ratio and titerefore correspond to coral titrombolites. ‘lite coral reef samples located below S2 slíow ratios up to 2.8, whereas tite ones located aboye líave ratios
down to 2.6.
4. BR pinnacle: Tite studied samples slíow a lower part (up te 12 m) dominated by microbial crusts (60 to 80 %, witit less titan 20% of coráIs) and an
upper part dominated by corals (less titan 20% of microbial crusts and 6070<Yo of corals). Only sample G, located 9 m aboye bottom reef, shows an
amount of microbial crust (30%) lower titan colonial forms (35%). It has been
not possible to recognize interior surfaces in tite reef core from outcrop observation. l--fowever, tlie comparison te tite otiter pinnacles, suggest tite location of S2 in tite boundary betwecn a Ioxver coral titrombolite area (ratios
ranging between 0.03 and 0.3) and tite upper coral reef one (ratios around 4).
Tite rcsultant data orí eacit pinnacle can be furtiter componed, establisiting
a correlation between tite insitore and offshore pinnacles (Fig. 9). Tite vertical zonation described aboye sitows a general similar trend in alí tlíe sampled
pinnacles, wlíiclí consists of an overa! inc—case of tite cf/mc ratio to tite top
of tite pinnacles. Tite upward mercase of tite corais in tite Jabaloyas reefs was
60
tora»
reela
cora¡-bearlng
ihnniboii¡sS
EH
~1
o
Fig. O
Cor reí ttion of the four soimpled piunacles boised on the Si oi»¡d 82 strrfoíces. showiug tire
latcral ‘s »nataju of te c»ulouial formns/microbiod críist raticx defining ctu-al-reef c,r coral thromb»,lit ¡c f tcws (see right coltionns in Kg. 8>.
Hg. 9 (u? reí >cio.r~ entre los cuatro pináculos muestreadts en base a las superfocíes Sí y 82, en
la cjue sc mucstra la variación Literal de la proporción formas coloniales/costras niicrobioinas
(ver 1 1)1 ulun is cíe la íu»rte derecha en la PÁg. 8)
TIre pinnacle reefr ofjabaloyas (Late Kimmeridgian, NE Spain)
53
previously reported by Giner and Barnolas (1979> and Leinfelder el al.
(1993). Stacked horizons wiIl similar cf/mc ratio separated by sharp surfaces are also recognized in tite studied pinnacles. On tite basis of tite intermediate Sí and S2 surfaces, a correlation between Ile pinnacles can be estajÁistaxi. Titree vertical zones are distinguished: (1> below Si, there are coral itrombolites, with variable proportion of corals; <2) between Sí and S2
surface, Ilere is some lateral variation on tite pinnacles: tite proximal ones
are dominated by colonial forms, whereas Ile distad ones are microbial crustdominated; (3) aboye 82 the microbial crust become searce, with cf/mc ratio
larger than 2.
TI lE ASSOCIATED FACIES
Tite vertical and lateral distriibution of Ile facies associations across tite
studied cross-section is shown in Fig. 3. As a whole, tite facies distribution
sitows a retrogradational stacking facies in tite lower part of tite parasequence, followed by a rapid progradation of facies in tite upper part of tite parasequence. Two man groups of inter-reef facies are found: grain supported facies in tite lower pad (Facies A and B), followed by mud-dominated facies in
tite upper part (Facies C). Facies O is found covering al! tite reef and inter-reef
facies, and titerefore they correspond to tite post-reef facies. 1 lowever, sorne
interfingering between Facies C and O also occur.
Tite boundary between tite grain- and mud-supported inter-reef facies is
located to tite lower part of tite pinnacles in tite offsitore seetions (BB section),
and to tite top in tite insitore sections (BO section, see Fig. (3). In titese proximal sections, tite líoundary is rnairked by a sitarp, burrowed (Thalassinoides)
ornd pon-Uy encrusted surface. la sorne outcrops, titis sm-face display some depositional siope towards tite flanks of tite pinnacles. tn tite BH outcrop (Fig.
4), tite boundary reaches a minimun higliness of 4 m aboye tite bottom of tite
pinnacles in Ile inter-reef areas. Titis highness inereases to tite flank of tite
pinnacle, reaching 8-9 ní. Moreover, titis surface has continuity in tite pinnacíe core (le. 52 surface).
FACIES A: IJF 0.1kM- ANO BIOCLASIIC l~’ACKSTONES TO GRAINSTONES
Facies A occurs below and laterally to tite more western pinnacles. It is
arranged both in massive and cross-laminated tabular beds 0.5 to 0.7 m titiek
and eross-beds up to 0.3 m thick. Tite peloids are variable in sitie and forní
np to 35% of tite volume of tite facies. Titere are also micritic intraclasts 2-3
mm in diameter, whicit consists of debris of tite reef microbial crust, incíndíng encrusting organisms such as «Tubi~hytes» inorronensis, Koski nobu/lina,
54
Ml urdí y B. i3ádenas
Bacinella, serpulids and bryozoans. Tite proportion of tite intraclasts ranges
froní 1 0 to 25 %.
Tite bioclasts forin np to 20% of tite total volume of tite facies and coiisists
of debris of corals (roundcd clasits of np to 3 cm iii diameter), bivalves. eclíinoids (Balanocidaris) and bentitic forains (lituolids). ln lower proportioii are
found otiter fossils sucit as gastropods, 1kTautiloculina oolithica, Cayeuxia, bryozoans. bracitiopods, clíaetetids, níiliolidae and solenoporacean algae.
ltxcí vs 13: 00.11 )A.l ..AND BTOCJÁSÁ 1< l’ACKS’ItNR TO ORAJNS’rt)NRS
Facies 13 is dic nsliore equival.ent of facies A. it is found below and latera!lv Lo tite more proximal pinnacle reefs. Facies 13 is arranged in tabular beds
(1.3 to 0.5 ní thiek. Cross-bedded lcvels up to 0.3 m thick also occur. The
ooíds forní np to 200/ti of tite total ‘solume of fixe facies. Titeir size is variable,
dispL u-mg diamcters up to 1 mm. Tite core of tixe ooids consists of sUicidastic. gralos aud skeletaL partides <bivalves, lituoUds, (iayeuxia, echinoids, gastrt)l)ods and Y. oolithica). They show 1)otit type 3 and 4 and alternation of
tvpc ,3 md mieritic coatings (classification after Strasscr, 1 986).
fLtc bioclxsts forin up to 300/o of tite facies a.nd inciude solenoporacean algae (xcix abundant), lituolids, corals, clíaetetids. bivalves, gastropods. Cayanta, ecitinoids, 1V. oolithica, brvozoans, serpuliós and miliolids. Tlíe facies
ma’»’ also contain up to 10% of both peloids aríd intraclasts of microbial crusts
similar to tite previously described iii facies Ik. Occasio.nally are also foií.n.d.
type í aud Y.! oncoids (c].assification after í)a.hanayake, 1977), sitowing skeletal cores (coráIs, bivalves, ec.hinoids, gastropods)
-
Facíns (2:
SKRI.JÚTAI. \VACKFSrONItS
kiries C ocettrs latera.Lly to tite upper paut of tite pinnacles and its overalí
Uhickness mercases offsitore. Althorigh. tíle top of tite FT section is cí-oded. ive
Nave. ¡ ¡íi.erprctcd that Facies C pinches oui to tIie more proxinial sections,
witere fíe pinnacie recis are also thougitt tobe absent (Fig. 3). Tite facies consísts of Lii rrowed tabular i)io.[nicrit.ic beds up Lo 0.3 m thick, alternatin.g witit
both ni ¡rl’» U veis and bioclastie levels incl.ud.ing debris of metazoan btíilders
(¡e to¡als and citactcLids) np to vi cm in diameter. Tite bioinicritic beds are
oní mping ox ti dic flanks of tite pinnacle rccfs.
11w skeleial debris ¡nay form up to 30 % of tite facies. CoráIs, (titaetetids
and u hmnords are tite more abundant skeletal grains, wIiem-eas otiter fossils like
hiv xli es líLuolids, gastropods, solenoptxracean algae,A. oolithica, miliolids, bryozoans ‘md serpulids are more searce. Tite facies also contain sifl of both cariton ite ‘md siuiciclastie grains. tntraelasts of microbial crasIs are also eommon.
TIre júnnacle regft ofjabaloyas (Late Kimmeñdgían, XIS Spain)
oía
O: PELOIDAL, OOIOAL
ANI) BiOCIASVI(.1 PALKSTONES AND CJRMNS’rONES
FACIES
Facies O is located on top of tite studied parasequence, aboye tite llorizon
witich includes tite pinnacle reefs. Tite loiver boundary of facies O is generally
a sitarp an even surface. Hoivever, in some outcrops (cg. BB and 13C seetions), some interiayering between facies D aud dic underlying biomicrites
(facies C) is observed (Hg. 3).
Facies O includes a wide spectrum of facies, defined by variable amounts
of peloids, ooids and skeletal grains. Tite facies domijíated by peloids corresponds lo peloidal aud bioclastie packstones aud peloidal grainstones. Tbey
form 0.5 to 1 ní titick beds, witb occasional cross-liedding. Tite facies contains np to 40% of peloidsand 250/ti of skeletal grains, mainly debris of lituolids, miiiolids, coráIs, gastropods (occasionaliy forming accumulations in disti-cte levels) and bivalves.
‘tite tíoid-dominated facies are ooidal and bioclastie packstones and
grainstones. Titey are arranged in 0.3-1 m tbick beds, locally cross-bedded
and eross-Iaminated. Tite ooids are mainly of type 3 (Strasser. 1986), are up
to 1 mm iii diarneter and generally dispiay siliciclastie cores. Tite skeletal
grains may forní up to 20% of Ile facies. Tite more abtindant fossils are biralves, gastropocJs, solenoporttceaii algae, inñíolids and lituoiids. Type 1 mM
II oncoids (Dalíanayake, 197’7) of 5 mm of mean diameter are occasionally
found.
Tite bioclastie facies are wackestones tú packstones and are arranged in
tabular beds 0.3 Lo 015 m thick. Tite more abundant skeletal grains are gastropods and soleííoporacean algae. Bivalves, Cayeuxia, coráIs, echinoids. Iituolids, níiliolids, brachiopods, dasycladacean algae (Acicularia) and N. oollíhica are fotiud in lower proportion. Most of titese bioclasts sitoív titin micritie coatings. Encrusted su rfaces with oysters aud accumulations of bivalves
givíng risc to a small patehes are occasionally found on titese facies.
INTERPRETATION
SEDíMEN’í’ARY REAl -MS IN Ti lE LATE KJ.MMERIDGIAN RAMP
Tlíe nature and distribution of Lite facies in tite studied parasequence,
allows tite reconstruction of tite sedimentary realms of tite Late Kimmeridgian carbonate ramp in tite Jabaloyas area (Fig. tú). Facies D is considered to
be deposited in inner ramp arcas (internal lagoon and marginal sand shoa]s),
whereas tite pinnacle reef arid associated facies (A, B, C) would growttí in tite
open and relatively deep mid ramp domains. Tite inner and mid ramp arcas
are placed aboye aud below fair iveatiter wave base respectively. The mid
56
Al. Aurelí y B. Bádenas
ramp areas are aboye storm wave base sea level, and titerefore periodieaily aiffected by high energy events (Burcitette and Wright, 1992).
Hg. lO.—Sedimentary model for [he Late Kimmeridgian carbonate rotmp in Pie Joibaloyas ares.
Fig. 10—Modelo de sedimentación poro» la rampa carbonatada del Kiniuoeridgieusc superior en
el sector de JabaJoyas
Two basic types of facies are recognized in tite mid ramp areas. Tite
more interna! domains are covered by grain-supported facies (facies A and
13), whereas tite outer realm of tite mid ramp is dominated by burroived,
mud-dominated facies, witich are indicative of lower energy environment
(facies C). Insitore, tite sediment is dominated by high energy ooids (type 3,
Strasser, 1986) and by a wide spectrum of skeletal grains. which are indicative of sitallow aríd open marine conditions (facies B). Offshore, tite grainsupported sedimenis are peloidaL and skeletal, including also a diversified
and open bentlíic community with forams, bivalves, solenoporacean algae
and eclíinoids (facies A>.
Scattered in tite mid ramp are found a set of patcit reefs. Tite elevation of
tite reefs aboye l)ottom floor was variable botit in time and in space. Based on
the BH section, where it is possible to examine tite relationsitip between coeval inter-reef facies and intermediate stages of growing of the pinnacle reef
(Hg. 4), tite maxiinum risc of the pinnacles aboye tite surrounding sediments
can be estimated to be around 4 lo 5 m. Tite elevation of tite patch reefs is reduced insitore. In tite more internal arcas of Ile mid ramp <Le., FT section)
only metric patch reef scattered between graln-supported oolithic and bioclastic facies are found.
Facies O is interpreted lo be originated in me- raníp aireas. Tite peloidal
and skeletal-dominated facies includes a benIlie community of gastropods,
miiolids, lituolids, bivalves and oysters, indicating partly restricted environ-
TIre pinnacle reciA ofJabaloyas (Late t{immeridgian, NE Spain)
57
ments. Titis restriction would be originated by tite presence of a belt of sand
shoals (oolititic and bioclastie facies), interpreted to be located in Ile transition between inner and mid ramp areas.
TI-lE PIMNACIÁ?
[<FF35
Tite relationship between tite reefs and tite associated facies exposed above sitows that Ile growing of tite pinnacles took place in mid ramp areas.
Giner and Barnolas (1979), Fezer (1988), Aurelí (1990), Nose (1995) and
Baumgártner and Reyle (1995) have proposed a similar setting for Ile reef
growing. The nature of tite organisms that constructed Ile reefs are also coiterent tú titAs assignnient (see Nose (1995) for details). In addition, tite associated micro-encrusters found commonly in the microbial crusts, wiIl Ba4nella, Lithocodium, Koskinobullina, «Tubiphylesx’ morronensis and serpulids,
are considered by Leinfelder el al. (1993> as representative of shallow ranip
areas.
Tite colonial forms are preserved in Ile reefs as debris of different size and
are only occasionallyfound in growth position. Tite breakage of tite skeletons
was due tú botit storm reworking and biocrosion. Part of the debris originated by these processes were accumulated in tite inter-reefs sediments or transported insitore. Accordingly, tite proportion of tite preserved metazoan builders in tite reef is lower titan the proportion during reef growing (Longman,
1981). l-Iowever, tite bulk of titese debris remains in the reefs, forming titeir
frameworks along lo tite microbial crusts.
Tite role of tite microbial crusts in Ile origin and development of Ile Late
durassic reefs has been examined in detail by Leinfelder el al. (1993, 1994>.
According to titese autitors, tite microbial crusts are of paramount importmce for Ile origin, stabiiitization and development of positive buildups. Tite
microbial crusts are binding and bounding togetiter the debris of tite metazoan builders, forming also variable proportions of Ile reef fabrie. Titese crusts
were rapidly itardened, as indicated by tite presence of borings on tite ernst itself. Tite development of tite microbial ernst is discontinuous, as it is shown
by both tite irregular intergrowing between peloidal or micritic fabrics and
tite presence of tite micro-encruster organisms.
Tite internal cavities, either left during tite reef growing or originated by
bioerosion, are rarely filled by marine or meteoric cements. Only some partially filled reef cavities (geopetais) have been later cemented by sparite. Most
of tite cavities are occupied by muddy (occasionally peloidal or ooidal) internal sediment. Titis mud may be originated cititer by bioerosion (Tueker and
Wright, 1990) or by filtering and baffling tite fine grain sediment suspended
in Ile surrounding marine waters. Arguments such as tite presence of ooids
or siliciclastie silt in tite muddy intemal sediment or tite occasional lamina-
58
14. Aurelí
y
J3• Bádenes
tion and gradatiori in tite peloidal fillings, demonstrate an external supply.
1 lowever, it is difficult to estimate itow mucit interna! sediment itas been originated cititer by bioerosion or by externa] supply.
DiSCUSSION: REEF GRO\VTH
AND SEA LIBVEL CHANCES
Tite general trend on tlie vertical and latera! reef zonation described above and tite inLer-reef facies distribution, aflows to discuss tite rclationship betiveen ttíe growing of the pinnacles asid Ile changes of sea level. Tite evolution
of tlíe studied parasequence titrougitout four successive sea level episodes is
sitown irí Fig. 11. Episodes 1 and 2 are coeval to a continnoas sea level rise
(Le. Lrarísgressive systems tract), witereas episodes 3 and 4 sliow tile facies
distribulion during tite subsequent stillstand of sea leve] (i.e., higbstand systenis tract) 11’ite evolutioíi in Fig. 11 itas been illustrated upwards from tite
ito.rizoií including tite reefs. Tite prexáous sandy, marly aud grain-supported
sitalloiv earboííates present in tite lower parL of tite sttídied sections (see Fig.
3) would represent a continuous flooding of tite ramp, from trajísitional to
sbailow marine environments.
-
TRANSCORIVSSIVE SYSTEMS
-rRÁCT
A. first episode corresponds to a fast rise of sea level iviticlí involved tite
initial flooding of tite carbonate ramp (Fig. 11.1). Tite top of this episode Corresponds to tite Sí surface. As a consequence of a rapid creation of accommodation in tite basin, a sedimentary starvation in tite mid ramp occurred.
Only tite fast vertical growing of some pinnacles is able Lo partly compensate
for tite accommodation. Stratal biostromes, ivith variable latera! extension,
also greív during titis episode. Tite local development of microbial crusts
produced tite stabilisatiou and bardening of tite substrata, allowing tite growing of tite coral forms in subsequent episodes (Leinfelder el al., 1993). Tite
partial reworkíng of tite microbial ernst is indicated by tite common presence of debris of tite ernst in tite coeval peloidal, oolithic and bioclastie facies A
and 13.
During Uds first episode tite reefs sitow widespread coral dírombolitie fabries. As indicated by Leinfelder e! al. (1993), tite main prerequisite for tite
occurrence of microbial crust is a eessation of tite background sedimentation
wtuch can be eommoniy tied to rises of sea level. 1 fowever, aecording to titis
autitor, low sedimentation rate is aÑo favorable for coral groívtit. Tite low
proporLion of corals and tite loív diversity of micro-encrusters during titis loiver epist)de are in(licativc of sorne restriction in tite manne envíronment. As
The pininicle reeJs ¿flahaloyas (Late Iúrníneridgian, PIE Spain)
59
explained by Leinfelder <1993) and Leinfelder e! al. <1993) a rise of tite dysaerobic waters due to lowering cireulation during sea level rises may exclude tite extensive growing of metazoans, witilst Ile euroxie microbes remxn.
Tite overail vertical growing of tite reefs followed and/or initiated during
tite continuing riser of sea level (Fig. 11.2). Tite inter-reef sedimentation recovered in tite intemal arcas of Ile mid ramp. Tite deposition of grain-supported facies A and 13 was coeval to tite reef development, as indicated by tite
I)resence of ooids and peloids in tite internal reef cavities. Both tite mercase of
tLíe background sedimentation aud tite recovery of Ile normal oxygenated
environment alter tite initial flooding of tite ni-np in tite more proximal areas, may explain tite rapid sitift from coral-titrombolitic to coral reefal fabries.
Titerefore, tite shaw boundary locally observed betíveen both types of reef fabrie in tite insitore pinnacles (e.g. Sí in ttíe BI) I)innacle) is likely to reflect
some nutrient and/or oxygen fluctuaLion.
Hoivever, titrombolitie fabries are stiiil dominant in tite offsitore reefs. Sedimentary rates were lower in tite external arcas of tite mid ramp, as indicated by tlíe offshore titickness reduction of Llie inter-reef facies. Tite coeval development of coral titrombolites and coral reef at apparentiy similar bathymetrie conditions, would refiect not only sorne latera! variation in Lhe oxygen
and/or nutrient content, but aÑo tlíe off-slíore decrease of tite sedimentary raLes across tite inid ramp area.
Wc líave placed Lite upper boundary of tite transgressive systems traet or
níaiximurn flooding surface on tite so-called S2 surface. Titis is a burroived
and encrusted surface covering tite grain supported facies A and 13 between
tite 131) and BI 1 sections. Tlíis surface is coeval tú tite development of tite fiat
surface witit mierobial crusts located some 9 m aboye tite bottom of tite more
proxiínal pinnacles (i.e. 82 surface. see Figs. 4, 5 and 6). Tite biomicritie inter-reef facies located off-sitore (facies C) are intensively burrowed, indicating
also some sedinientary condensation. Tite deerease of tite sedimentary rates
iii relation to tite increasing accommodation rates is also indicated by a retrogradational staeking pattern, ívitit tite progressive backsteeping of tite
rnud-supporLed facies (2.
1 liclislANIí SYSTEMS 1RACT
Tite rapid risc of tite sea level resumes at Ile onset of Ilis episode, dominated now by a sea level stabil ¡sation, witicit aillows tite recovery of Ile carbonate production. Tite successive observation of aggradational and progradational facies arrangement in tlíe sediments deposited during Uds sLillstand
episode, allows to difícrentiate between early ¿md late highstand systems
tract.
At tite onset of a first episode or early itighstand systems tract (Fig. 11.3)
¡
60
Al. Aurelí y B. Bádenas
¡So~
sc
FÉÁZ
e’
-‘~¶2~--
—1
4. LATE HIGHSTAND
3. EARLY HIE3HSTAND
2
2. MAXIMUM FLOODINS
1. INIT¡AL FLOODING
sA~»~. O
—
Ó
:~
fac es
fac¡esA
Fig. II
¡
<~~wísr;
¡
¡
increasing rol>,
¡
cl/m.c En Coral recia:
co»aI throsnbo¡ites
A
--
7éó~
¡
4m~
1000 ir,
—Evolution of tire pinnacle reefs ¿md associated facies relattd to sea level variation.
Fig. 11 —Evolución de los pináculos arrecifales y facies asociados en relación con las variaciones del nivel del mor.
TIre pinnacle reefs ofjabaloyas <Lale J-úmmeridgian, NE Spain)
61
titere was still an important accommodation available in tite inter-reef areas.
They were relatively deep sites, witicit become progressively filled up by tite
onlapping of tite offshore biomicrites. As a result, the elevation of Ile pinnacíes aboye bottom sediment was reduced. Qn Ile otiter hand, Ile restoration
of thc oxygenatcd environments during Uds bighstand episode allows tite recovery of Ile growing of tite colonial forms alí across tite studied pinnacles.
Titis results in some vertical aggradation of Ile reef aboye 52 surface. Tite aggradation of tite pinnacles, larger titan Ile accomimodation created, would
produce some sitallowing upward on them. Botit, tite composition of tite internal sediment found in tite reefs cavities and tite high proportion of debris
of colonial forms (mainly coráIs and chaetetids) in tite inter-reefs biomicrites,
indicate the coeval development of the reefs and the inter-reef biomicrites during Uds episode.
During tite late higitstand epísode (Fig. 11.4), Ile rapid progradation of
Ile inner ramp facies resulted in tite complete filling of tite available accom-modation. Titis progradation was favoured by botit tite relatively fiat arid
shallow topograpity of the mid ramp left after Ile filling of Ile inter-pinnacle
depressions and tite higit carbonate production. Skeletal and oolitbic levels
interbedded in the biomicritic inter-reef facies indicate tite progressive sitallowing upward of tite inter-reef areas. Over tiÉs skeletal levels are small coral
patcit reef developed.
FINAL REMARKS
1. Tlíe pinnacle reefs of tite Jabaloyas area sitow some vertical ¿md latera!
variation in tite relative proportion of microbial crusts and metazoari builders. Tite overalí pattern of reef zonation presented in our work is based on
vertical logs across four separated pinnacles, aiong to ficíd observation in intermediate reefs. However, titere are some lateral varibility in Ile reef fabrie
wititin individual reefs. Titis shouid be d.ue to coral aggressivity and, particularly, tú intemal differences in sedimentation (Leinfeder, per. com.). Therefore, Ile ratios of cf/mc presented in Figs.8 and 9, witicit are based on vertical logs along tite piinnacles, should not be taken as exael ratios. Also, in order to acitieve a more realistie pattern of Ile lateral variation of tite reef fabric
along to tite proximal-distal section, more intermediate reefs sitonid be evaluated under tite seope of Ilis work. However, we believe that Ile preliminary
results presented in titis work give a reliabie idea on Ile overall trending of
tite vertical and latera! reef fabrie variation. BoIl, tite similarity between Ile
vertical variation on alí tite sampled pinnacles and tite presence of correlatable horizons, which display comparable cf/mc ratios separated by discontínuity surfaces, give support to tIlis assumption.
2. Tite sedimentological analysis of tite reefs of Jabaloyas aud of titeir as-
62
Al. ¡1 u,-ell y .B. Bádenas
sociated facies presented in our work, itas aliowed to explain several aspects
related to titeir origin and deve]opment in the Late Kimmeridgian Iberian
carbonate rainp. Questions addressed in our work, sucit us tite relations.hip
betxveen reef and inter-reef facies or its evolution during successive sea level
variation along to a proxirnal-distaL section, gives additional information
aud support to tite results obtained in previous works, concerning tite faeL.ors witieh controlled tite origin and evolution of Líle tiipper Jurassic reefs
(see especiallv Leinfelder. 1993; Leinfelder el al., 1993, 1994; Baumgárt¡]er and. Revle, 1995 aud Nose, 1995). l-{esults reported in titese studies,
sucb us tlíe intense development of microbial ernst dite to very low background sediníentation rates amI to partial exelusion of corals by fiuctuating
oxygen/nutrieíít !evels related to sea leve! rises. are fiílly supported ‘»vitit
our data.
3. The studied sediments belong to a cyclic parasequence located in Lite
lower part of a titird order depositional sequence, witicit sparis froní Late
Kimrneridgian to Early Tititonian. Tite variation of aceominorlation deduced
from facies ana!vsis sitows a rapid initial sea level risc at tite onset of tite parasecínence, folloived by a later stillstand of sea level. Taking into account
1)otit tlíe nature of tite facies below aud abose tite pinnacles, tite mean tlíickness of tite stud ied parasequence and tite poonLy compactioií (>l)served in tIte
reef fabrie, tite total accommodaiton (Teated in tite basin froní tite initial developrnent cf tite reets to titeir late burial sitoií!d be around 20 rn. Titis arcommodation is a combníation of both, loca!. subsidence a.nd custatie variatiolls lost of tiíis sea level lise was concerítrated during tite deposition of tite
transgressive systems tract deposits, wbere it can be esti maled to be around
12-15 rn (see dashed arrows in Ng. 11, episodes Y and 2). Leinfelder (1993)
and Nose <1995) itave suggested an stroííg regional or global custatie control
on tUis risc of sea level.
1. Tite slíalioxv carbonate ramp developed at Jabalovas allows to anailyse
tite response to tite carbonate production on a carbonate ramp during a rapid
relative sea Jevel risc. Reduced carbonate production in tite studied Late Jurassic ramp during initial sea level risc resulted in a partly condensed section
in mi(I ramp arcas, folloxved by a laíídward shifL (backstepping) of the deeper
biomkritic facies. ¡Iowever, tite vertical aggradation of sorne reefs was able to
compensate for rnost of tite acconímodation ereated during sea level rise in
onter middle raffip arcas, resulting in a facies distribution similar to Llíe catcit
np type platforms defined l~ Keiídall and Schlager (1981). Duriííg late stages of rising sea level, carbonate production was recovered in sbal!ower areas, resulting in an aggradational stacking pattern (see lateral transition between facies A and B in Fhg. Ii .2). 1 liglí carbonate productivitv du ring tite ultenor slillstand of sea level resulted in tite facies agradation in tite iííter-reef
facies foliowed by a fast progradational pattern (i.e.. earlv and itigitstand systems tracis).
-
TIre pinnacle ¡-cefi qfJabaloyas (Late Khnrneridgian, NT SPain)
63
ACKNOWLEI)GMENTS
Finornciofl support was I4E)Uáed by fije project DOICYT PB 92-0862. Tbe work of 3. 8. was
f¡.rnded br a grant of tire Institutt» de Estc,dios Turolenses. Ibis researcb has greatly benefited
from disct,ssi.ons oiíwl revie’svs by 1. Nt. Martín, A. Meléndez otiíd R. R. Leinfeltíer.
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Manuscrito recibido: 29 dejunio 1995
Manuscrito aceptado:1O deJulio 19.96