Geology Reference
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Fig. 18.10 Simplifi ed geological map of the present-day Tremp-
Graus Basin showing the location of the outcropping Alveolina
Limestone and the Roda, Capella and Pano Fms (modifi ed after
Serra-Kiel et al. 1994 , who used data from Fonnesu 1984 , Samsó
1988 and Tosquella 1988 , and Cuevas Gozalo 1989 ) . The box
indicates the area in part covered by Fig. 19.11a
Mutti et al. ( 1972, 1973, 1975 ) divided the forma-
tion into three units (lower, middle and upper). The
lower and upper units consist of a series of tabular sand-
stone bodies characterised by an upward-coarsening
grain-size profi le and a sigmoidal geometry of accre-
tion surfaces (Mutti et al. 1985 b ; Olariu et al. 2008a ) .
The upper unit of the Baronia Fm is interpreted to have
been deposited in shallower water, subject to stronger
tidal currents than the lower unit (Mutti et al. 1985b ) .
Wonham ( 1993 ) divided the Baronia Fm into two
low-order sequences. The lower sequence is com-
posed of a transgressive estuary succession with barri-
ers at the mouth of the estuary developed above an
erosional unconformity formed by lowstand fl uvial
incision. A tripartite estuarine facies distribution was
recognized with ebb-tidal delta deposits in the distal
western part of the basin and bay-head delta bars in
the proximal astern part of the basin. Higher-order
relative sea-level changes resulted in repeated basin-
ward shifts of facies and a successive broadening of
the estuary in time. The estuary deposits are overlain
by a relatively thin (up to 12 m) succession of trans-
gressive offshore and shelf deposits. The upper
sequence is also formed by a tide-dominated estuary
overlying an unconformity formed by lowstand fl uvial
incision (Wonham 1993 ). The wide estuary had no
barriers at its mouth and was fi lled with compound
cross-stratifi ed beds formed by ebb- and fl ood-directed
cosets containing tidal bundles; water depths were
interpreted to decrease from about 20 m at the base to
5-10 m at the top. The transgressive estuary fi ll is
overlain by a retrogradational set of lower shoreface
and offshore deposits (Wonham 1993 ) .
The Ametlla Fm (Mutti et al. 1972, 1973 ; Figs. 18.4 ,
18.5 and 18.11 ) rests conformably on the offshore
siltstones of the Passarella Fm. It is informally
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