Stage

Facies ID

DESCRIPTON

INTERPETATION

1

LP-f_n+1-ps

Pleistocene sediments (poorly compacted) cropping out west of Lagoa do Peixe escarpment (Barrier III).

Pleistocene sediments cropping out at the footwall top west of fault escarpment (Barrier III).

1a

LP-f_n+1-pf

Radarfacies underlying the lower lagoonal unit, displays regular reflections which are truncated (toplap-offlap) by its upper boundary.

Pre-fault radarfacies undergone hangingwall collapse and erosion.

LP-s_n+1-gf

Upward concave listric geometry surface that truncate Pleistocene sediments (west) and lower lagoonal unit (east).

Listric gravitational growth fault. See also associated branching normal faults.

LP-s_n+2-et

Offlap-toplap for reflectors underlying lower lagoonal unit; maybe an erosional truncation.

An erosional surface developed on the down-throwing hangingwall before fault controlled lagoonal accumulation.

2

LP-f_n+2-pe

Convex upward arcuted lower lagoonal unit, displaying onlap for lowermost reflections in the thickest zones, close to listric surface, and parallel reflections for uppermost strata.

Lagoonal accumulation during the first stage of fault displacement resulted in its convex geometry and greater thickness close to fault surface.

LP-s_n+3-ol

Surface at the top of the lower lagoonal unit, in the outcropping peat layer, showing onlap reflections for overlying radarfacies.

An increase in water depth giving rise to onlap of horizontal sedimentary layer on both sides in the lagoon depocenter.

3

LP-f_n+3-lag

Horizontal reflections in a hangingwall triangular area close to listric surface, showing onlap upon lower lagoonal unit and listric surface.

Localized sediment accumulation while fault displacement advanced, during a second stage of fault displacement, clogging Lagoa do Peixe depocenter (triangular wedge).

LP-s_n+4-dl

Discrete onlap-downlap features upon previous radarfacies on both margins of the Lagoa do Peixe.

Surface defining the vanishing stage of fault displacement, and the third stage of sediment accumulation in the Lagoa do Peixe.

4

LP-f_n+4-lag

Upward arcuated reflections at both Lagoa do Peixe margins, showing alternating onlap-downlap and toplap-offlap features.

Third stage of lagoonal sediment accumulation, characterized by the interbedding of lagoon sediments and sands from emersed areas on both sides of the Lagoa do Peixe.

5

LP-f_n+5-es

Dipping sinuous reflections in the Lagoa do Peixe escarpment, showing discrete downlap with lagoon sediment reflections.

Erosional degradation of the fault escarpment and deposition as interbedded layer of sands and lagoon sediments.

LP-s_n+n-df

Minor truncation of inner reflections of radarfacies.

Minor listric normal faults merging into master one, or diachronic synthetic and antithetic normal faults.

LP-s_n+5-dl

Irregular surface underlying recent dune sediments.

Surface upon which recent dune sediments prograde.

6

LP-f_n+6-dm

Horizontal and steeply dipping sigmoidal reflections, as also as thin horizontal reflection near the topographic surface.

Recent dunes and thin wind cover overlying previous sedimentary radarfacies: 6a—steeply dipping reflections: lateral limbs of recent dunes; 6b—horizontal reflections: frontal dune strata, and thin wind covers.

Types of radarfacies (f)

Types of boundary surfaces ( s )

ps = Pleistocene sediments

gf = growth fault

pf = pre-fault unit underlaying lower lagoonal

et = erosional truncation

pe = lower lagoonal, underlying peat layer

ol = onlap

lag = sediments clogging the lagoon

dl = downlap

es = erosional sediments close to escarpment

df = diachronic normal faults

dm = recent dunes and thin wind covers (Upper Holocene)