VIDAL ROMANI, J.R. (1) YEPES TEMIÑO, J (1) FERNANDEZ MOSQUERA, D. (1) DE UÑA, E. (2) & TWIDALE, C.R. (3)
(1) Ins i u o Uni e si a io de Xeolóxia "Isid o Pa ga Pondal", Uni e si y o A Co uña, 15071-A Co uña, Spain
(2) Depa men o Geog aphy, Uni e si y o Vigo, 32004-Ou ense, Spain
(3) Depa men o Geology and Geophysics, Uni e si y o Adelaide, Adelaide-5005, Sou h Aus alia, Aus alia
ROCK OF AGES
Abs ac
G ani e is emplaced deep in he Ea h's
c us . I cools and c ys allises and is
subjec ed o he mal and magma ic e en s,
and o ecu en s esses. I de elops
ex u es o ab ics as well as s ain pa e ns
which, as e osion b ings he ock mass
nea he su ace, ind exp ession in a ious
ac u e se s and sys ems.
F ac u es a e a enues o weakness exploi ed
by mois u e when he ock mass in e cep s
he g oundwa e zone (pa icula ly in he zone
700-800 m below he land su ace). The
pa e ns o hese ac u es a e imposed on
he shape o he land su ace a a ious scales.
Subsu ace wea he ing pa e ns a e de e mined
by ac u e densi y and a he mesoscale ind
exp ession, o example, in bo nha d s and a
he mic o in cle s o slo s. Once exposed o
epigene wea he ing and e osion bo nha d s
may, depending on clima e and deg ee o
exposu e, be ans o med in o nubbins o
kopjes. Ancien s ains and ab ics a e exploi ed
o p oduce gu e s, basins, and linea ions.
Tec onism con inues so ha new sca ps and
pop-ups de elop. Clima ic changes lea e
behind elic ea u es alien o hei new
en i onmen .
Thus g ani e o ms can be assigned di e en
ages: a gene ic age whe e mo phology is
ela ed o pas ec onic, he mal o magma ic
e en s; a p e-exposu e age whe e de eloped
by subsu ace wea he ing; an epigene age
whe e shaped a he land su ace; an inhe i ed
age whe e shaped by p ocesses ela ed o
p e ious clima ic egimes. Thus many
land o ms a e mul is age. The e en s o which
hey owe hei mo phology can in some
ins ances be aced back a in o Ea h
ch onology. (250 wo ds).
Conclusions
The i s p oblem in o de o unde s and he
elie de eloped on g ani ic ocks is o de e mine
whe he he o ms a e based on exogenous o
endogenous o igin ea u es o ally o pa ially.
I is also impo an o know he a e a which
a ious exogenous e osi e agen s esponsible o
he o ms (wa e , ai , ice) ac . The age o he o ms
gi es he age o he su ace o e which hey
de elop, as he e will be ound olde o ms,
ob iously, o e he oldes su aces, hough all he
o ms may disappea i he deg ading o he
su ace bea ing hem is in ense enough and long
in ime. So, i is unde s ood ha he e exis s a
g ea unce ain y in geologically de ining alue,
age, o igin and meaning o a su ace i we backed
on he o ms de eloped o e i . Anyway, he oldes
age o a o m should be logically in e ed om he
pe og aphical-s uc u al his o y o he ock. The
o he ages, which may be gi en, co espond o he
di e en phases la e o he exposu e o he ock
in su ace.
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